Method and system for generating, applying, and defining a pattern6851105
Abstract
The present invention relates a method and systems for generating, applying and defining patterns for software development. The software development tool receives an indication of a pattern, generates software code reflecting the pattern, and stores identification information for the pattern in a comment associated with the generated software code. The software development tool receives an indication of the software element, determines whether the software element is capable of playing the role, and when it is determined that the software element is capable of playing the role, designates that the software element plays the role in the pattern. The software development tool displays a plurality of software elements to a user, receives an indication of a selected one of the plurality of software elements, receives an indication of a user-defined pattern role that the selected software element plays in a pattern, and stores the plurality of software elements as the pattern.
Claims
What is claimed is:
1. A method in a data processing system having a plurality of patterns, wherein each of the plurality of patterns has an associated element type, the method comprising the steps of:
receiving an indication of an element type, wherein the element type is a class, link, or any known object-oriented component of a software program;
displaying a matching one of the plurality of patterns, the matching pattern having an associated element type that matches the received element type;
receiving from a user an indication of a selection of the matching pattern;
receiving an indication of a variation;
modifying the matching pattern based on the variation;
receiving an identification of a language; and
generating software code reflecting the modified matching pattern, wherein the software code is generated in the language.
2. The method of claim 1 further comprising the step of determining whether the variation is suitable for the matching pattern before modifying the matching pattern.
3. The method of claim 1, further comprising the step of storing identification information for the matching pattern in a comment associated with the generated software code.
4. The method of claim 1, wherein the step of generating includes the steps of determining a location for storing the generated software code and storing the generated software code at the location.
5. A method in a data processing system having a pattern, wherein the pattern has a first participant playing a first role in the pattern and a second participant playing a second role in the pattern, the method comprising the steps of:
receiving an indication of a first of a plurality of software elements, wherein the first of the plurality of software elements is a substantiation of an element type; wherein the element type is a class, link, or any known object-oriented component of a software program;
determining whether the first software element is capable of playing the first role;
when it is determined that the first software element is capable of playing the first role;
determining whether a second of the plurality of software elements is capable of playing the second role, wherein the second of the plurality of software elements is a substantiation of an element type;
when it is determined that the second software element is capable of playing the second role;
designating that the first software element plays the first role in the pattern; and
designating that the second software element plays the second role in the pattern.
6. The method of claim 5, further including the step of, when it is determined that the second software element is not capable of playing the second role, designating that a missing participant plays the second role in the pattern.
7. The method of claim 5, wherein the step of designating the first software element includes the steps of:
detecting a portion of the first software element; and
replacing the portion of the first software element with at least a portion of the first participant.
8. The method of claim 5, further comprising the steps of:
receiving an indication of a variation for the first participant; and
modifying the first participant with the variation before the first software element is designated to play the first role in the pattern.
9. The method of claim 8, further comprising the steps of:
receiving an indication of a second variation for the second participant; and
modifying the second participant with the second variation before the second software element is designated to play the second role of the pattern.
10. The method of claim 5, further comprising the step of storing identification information for the pattern in a comment associated with the software code.
11. A method in a data processing system for creating a pattern having a first particular with a first role name, and a second particular with a second role name, wherein the pattern is based on code having a first software element with a first coded name and a second software element with a second coded name, the method comprising the steps of:
receiving an indication of the first software element, wherein the first software element is a substantiation of an element type; wherein the element type is a class, link, or any known object-oriented component of a software program;
receiving an indication that the first software element corresponds to the first participant;
replacing the first coded name of the first software element with the first role name of the first participant;
receiving an indication of the second software element, wherein the second software element is a substantiation of an element type;
receiving an indication that the second software element corresponds to the second participant;
replacing the second coded name of the second software element with the second role name of the second participant; and
storing the code with the first coded name and the second coded name as the pattern.
12. A computer-readable medium containing instructions for controlling a data processing system to perform a method, the data processing system having a plurality of patterns, wherein each of the plurality of patterns has an associated element type, the method comprising the steps of:
receiving an indication of an element type, wherein the element type is a class, link, or any known object oriented component of a software program;
displaying a matching one of the plurality of patterns, the matching pattern having an associated element type that matches the received element type;
receiving from a user an indication of a selection of the matching pattern;
receiving an indication of a variation;
modifying the matching pattern based on the variation;
receiving an identification of a language; and
generating software code reflecting the modified matching pattern, wherein the software code is generated in the language.
13. The computer-readable medium of claim 12, wherein the method further comprises the step of determining whether the variation is suitable for the matching pattern before modifying the matching pattern.
14. The computer-readable medium of claim 12, wherein the method further comprises the step of storing identification information for the matching pattern in a comment associated with the generated software code.
15. The computer-readable medium of claim 12, wherein the step of generating includes the steps of determining a location for storing the generated software code and storing the generated software code at the location.
16. A computer-readable medium containing instructions for controlling a data processing system to perform a method, the data processing system having a pattern, wherein the pattern has a first participant playing a first role in the pattern and a second participant playing a second role in the pattern, the method comprising the steps of:
receiving an indication of a first of a plurality of software elements, wherein the first of the plurality of software elements is a substantiation of an element type; wherein the element type is a class, link, or any known object-oriented component of a software program;
determining whether the first software element is capable of playing the first role;
when it is determined that the first software element is capable of playing the first role;
determining whether a second of the plurality of software elements is capable of playing the second role, wherein the second of the plurality of software elements is a substantiation of an element type;
when it is determined that the second software element is capable of playing the second role;
designating that the first software element plays the first role in the pattern; and
designating that the second software element plays the second role in the pattern.
17. The computer-readable medium of claim 16, wherein the method further includes the step of, when it is determined that the second software element is not capable of playing the second role, designating that a missing participant plays the second role in the pattern.
18. The computer-readable medium of claim 16, wherein the step of designating the first software element includes the steps of:
detecting a portion of the first software element; and
replacing the portion of the first software element with at least a portion of the first participant.
19. The computer-readable medium of claim 16, wherein the method further comprises the steps of:
receiving an indication of a variation for the first participant; and
modifying the first participant with the variation before the first software element is designated to play the first role in the pattern.
20. The computer-readable medium of claim 19, wherein the method further comprises the steps of:
receiving an indication of a second variation for the second participant; and
modifying the second participant with the second variation before the second software element is designated to play the second role of the pattern.
21. The computer-readable medium of claim 16, wherein the method further comprises the step of storing identification information for the pattern in a comment associated with the software code.
22. A computer-readable medium containing instructions for controlling a data processing system to perform a method, the data processing system having a pattern having a first participant with a first role name, and a second participant with a second role name, wherein the pattern is based on code having a first software element with a first coded name and a second software element with a second coded name, the method comprising the steps of:
receiving an indication of the first software element, wherein the first software element is a substantiation of an element type; wherein the element type is a class, link, or any known object-oriented component of a software program;
receiving an indication that the first software element corresponds to the first participant;
replacing the first coded name of the first software element with the first role name of the first participant;
receiving an indication of the second software element, wherein the second software element is a substantiation of an element type;
receiving an indication that the second software element corresponds to the second participant;
replacing the second coded name of the second software element with the second role name of the second participant; and
storing the code with the first coded name and the second coded name as the pattern.
Description
FIELD OF THE INVENTION
The present invention relates generally to data processing systems and, more particularly, to methods and systems for generating, applying, and defining patterns for software development.
BACKGROUND OF THE INVENTION
Patterns are a literary form of software engineering problem-solving discipline. The goal of patterns within the software community is to create a body of literature to help software developers resolve recurring problems encountered in various domains (e.g., software architecture and design, and software development processes and organizations) throughout all of software development. Patterns help create a shared language for communicating insight and experience about the recurring problems and their solutions to promote proven techniques while avoiding "re-inventing the wheel."
In general, a pattern is the abstraction from a concrete form that keeps recurring in specific non-arbitrary contexts. Each pattern has at least one participant, and each participant plays a role in the pattern. For example, one well-known pattern is an adapter pattern. The adapter pattern solves the recurring problem of allowing classes, which could not otherwise work together, to work together because of incompatible interfaces. As is well known in object-oriented programming, a class is a blueprint used to create an object that has a known identity, state, and behavior. An interface is an abstract class or a Java.TM. interface that unrelated objects can use to interact with one another. It defines a set of method signatures, but does not implement them. A class that implements the interface agrees to implement all of the methods defined in the interface. The adapter pattern identifies the following as participants in its pattern: a client class, a target interface, an adapter class, and an adaptee class. The roles of these participants in the adapter pattern are described as follows. The client class calls methods associated with the target interface. The adaptee class has a method that a software developer wants the client class to call, but the adaptee's method is not supported by the target interface. Rather than modify the adaptee class to implement the target interface, which may not be an option if the software developer doesn't have the source code for the adaptee class, the software developer manually codes the adapter class participant to implement the target interface such that it calls the adaptee class method. This effectively delegates the method call from the client to the adapter so that the client class can remain independent from the adaptee class. Following the adapter pattern to delegate method calls made through a single interface is especially important where a client class needs to call multiple methods from different classes that are not associated with the single interface.
Software visionaries have published descriptions of a number of patterns in addition to the adapter pattern that solve a variety of common design problems faced by software developers. The published descriptions typically utilize the well-known Unified Modeling Language (UML) to graphically illustrate a pattern. UML is a general-purpose notational language for visualizing, specifying, constructing, and documenting complex object-oriented software systems. UML is more clearly described in the following references, which are incorporated herein by reference: (1) Martin Fowler, UML Distilled Second Edition: Applying the Standard Object Modeling Language, Addison-Wesley (1999); (2) Booch, Rumbaugh, and Jacobson, The Unified Modeling Language User Guide, Addison-Wesley (1998); (3) Peter Coad, Jeff DeLuca, and Eric Lefebvre, Java Modeling in Color with UML Enterprise Components and Process, Prentice Hall (1999); and (4) Peter Coad, Mark Mayfield, and Jonathan Kern, Java Design: Building Better Apps & Applets (2nd Ed.), Prentice Hall (1998).
These literary descriptions and graphical representations identify the following elements of a pattern: a meaningful pattern name that reflects the knowledge and structure of the pattern, the underlying problem solved and the context in which the problem seems to recur, the solution in terms of its participants (e.g., classes and objects) and the relationships between its participants (e.g., static and dynamic rules for composition, inheritance, and instantiation that generally dictate the roles of pattern participants), and the ramifications of applying the pattern (e.g., tradeoffs based on chosen design pattern alternative). It is up to the software developer to manually generate the code corresponding to the pattern and tailor it to the given application or project. This manual generation of a pattern instance suffers from a number of problems: first, it is time-consuming, tedious, and subject to human error; and second, a software developer that is behind in his work will typically skip commenting his code to reflect the use of a common pattern. Hence, other software developers looking to make use of or replace the common pattern cannot easily locate it within the existing code. Conventional software development tools do not address these problems.
Software visionaries have also published techniques to follow for redesigning unwieldy program code prior to or concurrent with adding new functionality that may otherwise add to the complexity of the existing program. These techniques are collectively known as "refactoring." Refactoring rejuvenates software by improving the structure and performance of existing software without changing the behavior of the software. When refactoring, the software developer typically takes manual, incremental steps to improve the structure of existing code to reduce complexity and avoid prolonged debugging. Such incremental steps may include renaming a method, moving a field from one class to another, or consolidating two similar methods in a superclass. New functionality is generally added after refactoring.
Applying a pattern to existing code combines refactoring with adding new functionality to improve the design of existing code. When applying a pattern, a software developer follows published instructions for generating the known pattern, but manually ascertains what elements of the preexisting code need to be modified or deleted (i.e., refactoring) as well as what elements of the pattern need to be added (i.e., additional functionality) to implement the pattern. Conventional software development tools do not provide support for applying a pattern to existing code. The developer also may deem a portion of the existing code as an undesirable or bad pattern that needs to be redesigned. Faced with the problem of redesigning a bad pattern, the developer typically surveys the existing code to detect any instances of the bad pattern and then manually applies a selected pattern to transform the code for each instance of the bad pattern. Conventional software development tools lack the capability to address these problems.
Finally, software developers often produce reliable and proven program code segments that can be shared between projects and with other developers. Typically, the software developers need to document and advertise the use of this proven program code segment to propagate its continued use. In such cases, the software developer takes the manual steps to copy and paste the proven program code segment into a new project. Conventional software tools lack the ability to assist in automating and publicizing the available patterns/code segments. Thus, there is a need in the art for a tool that avoids the foregoing limitations of conventional software development tools.
SUMMARY OF THE INVENTION
Methods and systems consistent with the present invention provide an improved software development tool that overcomes the limitations of conventional software development tools. The improved software development tool generates a pattern instance to offer a tailored and documented pre-emptive solution to a common software design problem, applies a pattern to a portion of existing code to improve the design of existing code, and defines a user pattern from existing code to provide a developer with the capability to capture a proven pattern for reuse. Patterns that are generated or applied have pattern information embedded in an associated comment by the improved software development tool to allow these patterns to easily be detected both textually and through the graphical diagrams to facilitate communicating the pattern's existence an for future design improvements.
In accordance with methods and systems consistent with the present invention, a method is provided in a data processing system. The method receives an indication of a pattern, generates software code reflecting the pattern, and stores identification information for the pattern in a comment associated with the generated software code.
In accordance with methods and systems consistent with the present invention, a method is provided in a data processing system having a pattern The pattern has a participant playing a role in the pattern. The method receives an indication of the software element, determines whether the software element is capable of playing the role, and when it is determined that the software element is capable of playing the role, designates that the software element plays the role in the pattern.
In accordance with methods and systems consistent with the present invention, a method is provided in a data processing system. The method displays a plurality of software elements to a user, receives an indication of a selected one of the plurality of software elements, receives an indication of a user-defined pattern role that the selected software element plays in a pattern, and stores the plurality of software elements as the pattern.
In accordance with methods and systems consistent with the present invention, a method is provided in a data processing system having source code. The method detects a first pattern in the source code, and replaces the first pattern with a second pattern that is different than the first pattern.
Additional implementations are directed to systems and computer devices incorporating the methods described above. It is also to be understood that both the foregoing general description and the detailed description to follow are exemplary and explanatory only and are not restrictive of the invention, as claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an implementation of the invention and, together with the description, serve to explain the advantages and principles of the invention. In the drawings,
FIG. 1 depicts a block diagram of a data processing system suitable for practicing methods and systems consistent with the present invention;
FIG. 2 depicts a flow chart illustrating an exemplary process performed by the software development tool in FIG. 1 for generating a pattern instance;
FIG. 3 depicts an exemplary GUI screen for initiating the generation of a pattern and for showing both a graphical and a textual view of the pattern instance generated by the software development tool in FIG. 1;
FIG. 4 depicts an exemplary screen showing a list of pattern options that the software development tool in FIG. 1 may generate based on a class element type and showing configurable properties and parameters that the software development tool in FIG. 1 may use to generate the selected pattern;
FIG. 5 depicts an exemplary screen showing other configurable properties and parameters that the software development tool in FIG. 1 may use to generate an adapter pattern;
FIG. 6 depicts another exemplary screen showing other configurable properties and parameters that the software development tool in FIG. 1 may use to generate a Java Bean pattern;
FIG. 7 depicts an exemplary screen showing a request by the software development tool in FIG. 1 to provide a special pattern property in order to generate a specific pattern;
FIG. 8 depicts an exemplary screen showing an example response from the software development tool in FIG. 1 after determining that a selected pattern with a variation based on a change to configurable properties or parameters may not be applied to the selected element;
FIG. 9 depicts an exemplary screen showing the source code generated by the software development tool in FIG. 1 in response to the selected Singleton pattern of FIG. 4 with the variation that Singleton and Singleton Factory properties have the same value;
FIG. 10 depicts an exemplary screen showing the source code for the Singleton class generated by the software development tool in FIG. 1 in response to the selected Singleton pattern of FIG. 4 with the variation that Singleton and Singleton Factory properties do not have the same value;
FIG. 11 depicts an exemplary screen showing the source code for the Singleton Factory class generated by the software development tool in FIG. 1 in response to the selected Singleton pattern of FIG. 4 with the variation that Singleton and Singleton Factory properties do not have the same value;
FIG. 12 depicts an exemplary GUI screen for initiating the generation of a link pattern and for identifying the two nodes between which the software development tool in FIG. 1 will generate a selected link pattern;
FIG. 13 depicts an exemplary screen showing a list of pattern options that the software development tool in FIG. 1 may generate based on a link element type, and showing configurable properties and parameters that the software development tool in FIG. 1 may use to generate the selected pattern;
FIG. 14 depicts an exemplary screen showing the source code generated by the software development tool in FIG. 1 in response to the selected pattern of FIG. 13;
FIG. 15a depicts a flow chart illustrating an exemplary process performed by the software development tool in FIG. 1 for applying a pattern to a portion of existing code;
FIG. 15b depicts a flow chart illustrating an exemplary process performed by the software development tool in FIG. 1 for applying a pattern to a portion of existing code;
FIG. 16 depicts an exemplary screen showing a selected class element within a portion of existing code prior to the software development tool in FIG. 1 applying a selected pattern to transform the portion;
FIG. 17 depicts an exemplary screen showing a list of pattern options that the software development tool in FIG. 1 may, apply to the selected class element in FIG. 16, showing configurable properties and parameters that the software development tool in FIG. 1 may use to apply the selected pattern, and showing a suggested pattern role for the selected class element;
FIG. 18 depicts an exemplary screen showing a first portion of the transformed source code and its corresponding graphical representation generated by the software development tool in FIG. 1 in response to applying a variation of the selected Singleton pattern to the selected class element in FIG. 16;
FIG. 19 depicts an exemplary screen showing a second portion of the transformed source code and its corresponding graphical representation generated by the software development tool in FIG. 1 in response to applying a variation of the selected Singleton pattern to the selected class element in FIG. 16;
FIG. 20 depicts an exemplary screen showing another variation in the configurable properties and parameters that the software development tool in FIG. 1 may use to apply the selected Singleton pattern;
FIG. 21 depicts an exemplary screen showing the transformed source code for one Singleton pattern participant generated by the software development tool in FIG. 1 in response to applying another variation of the selected Singleton pattern shown on screen 1900 in FIG. 19 to the selected class element in FIG. 16;
FIG. 22 depicts an exemplary screen showing the transformed source code for a second Singleton pattern participant generated by the software development tool in FIG. 1 in response to applying another variation of the selected Singleton pattern to the selected class element in FIG. 16;
FIG. 23 depicts an exemplary screen showing configurable properties and parameters that the software development tool in FIG. 1 may use to apply an Observer pattern to the selected class element in FIG. 16, and showing a suggested pattern role for the selected class element;
FIG. 24 depicts an exemplary screen showing a list of pattern options that the software development tool in FIG. 1 may apply to a selected link element in FIG. 16 and showing configurable properties and parameters that the software development tool in FIG. 1 may use to apply the selected pattern;
FIG. 25 depicts a flow chart illustrating an exemplary process performed by the software development tool in FIG. 1 for capturing a user-defined pattern from existing code;
FIG. 26 depicts an exemplary dialog box that the software development tool in FIG. 1 may use to display a user identified pattern participant and to receive a role to be assigned to the identified pattern participant;
FIG. 27 depicts an exemplary dialog box that the software development tool in FIG. 1 may use to display a user identified pattern participant and to receive a role to be assigned to the identified pattern participant;
FIG. 28 depicts a data structure of the language-neutral representation created by the software development tool in FIG. 1;
FIG. 29 depicts representative source code;
FIG. 30 depicts the data structure of the language-neutral representation of the source code of FIG. 29; and
FIG. 31 depicts a flow chart illustrating an exemplary process performed by the software development tool in FIG. 1 to produce pattern code.
Reference will now be made in detail to the description of the invention as illustrated in the drawings. While the invention will be described in connection with these drawings, there is no intent to limit it to the embodiment or embodiments disclosed therein. On the contrary, the intent is to cover all alternatives, modifications, and equivalents included within the spirit and scope of the invention as defined by the appended claims.
DETAILED DESCRIPTION OF THE INVENTION
Methods and systems consistent with the present invention provide an improved software development tool that generates a pattern instance, that applies a pattern to a portion of existing code to improve the design of the existing code, and that can be used to create a new pattern from existing code. The improved software development tool saves development time and expense while promoting better design practices by allowing a developer to automatically generate a pattern on command and to automatically apply the pattern to existing code to improve the design of the code. Thus, this system enables the developer to avoid having to interpret and manually implement the pattern provided in a book, and to avoid the risk of incorrectly implementing the pattern. Furthermore, the improved software development tool enables a programmer to capture a good design and make it into a reusable pattern.
Patterns allow software developers to implement sound engineering architecture and design for resolving common, recurring problems encountered throughout all of software development. Through the use of pattern generation in accordance with methods and systems consistent with the present invention, a developer can organize, document, and produce more maintainable software. In addition, a developer can manually or automatically detect an undesirable pattern and transform the undesirable pattern into a desirable one.
Implementation Details
FIG. 1 depicts a data processing system 100 suitable for practicing methods and systems consistent with the present invention. Data processing system 100 includes a memory 102, a secondary storage device 104, an I/O device 106, and a processor 108. Memory 102 includes a software development tool 110 for generating, applying, and defining a pattern for a software project 112, which is stored in the secondary storage device 104. The software project 112 comprises source code in at least one file which, when compiled, forms a sequence of instructions to be run by the processor 108. Software development tool 110 also includes a transient meta model (TMM) 114 that is generated by the software development tool to store a language-neutral representation of the source code for the software project 112. Software development tool 110 further includes a plurality of pattern program modules 116 that contain instructions that the software development tool performs to generate or apply a respective pattern as described herein. One skilled in the art will recognize that data processing system 100 may contain additional or different components.
Although aspects of the present invention are described as being stored in memory, one skilled in the art will appreciate that these aspects can also be stored on or read from other types of computer-readable media, such as secondary storage devices (e.g., hard disks, floppy disks, or CD-ROM); a carrier wave from a network, such as the Internet; or other forms of RAM of ROM either currently known or later developed.
Generating a Pattern Instance
To generate a pattern instance, the software development tool 110 supports the fir definition of a pattern using programming language statements or instructions that are encapsulated in a program module for each pattern. The programming language may be any object-oriented programming language, such as the Java.TM. programming language or C++. The program module may be a class that is compiled with the software development tool 110. Alternatively, the program module may be a script file, which is well known in the art. The script file will be interpreted by the software development tool at runtime. For the software development tool to generate a pattern instance or apply a pattern to existing code as described below, each pattern implements methods 2710 defined in a Source Code Interface (SCI) pattern interface 2700 shown in FIG. 27. As described herein, the software development tool performs the apply method 2718 for a pattern to invoke the transient meta model (TMM) to create or change source code corresponding to the pattern in a software project 112.
The TMM that is generated by the software development tool is described in greater detail in U.S. patent application Ser. No. 09/680,063, entitled "Method And System For Developing Software," that has been previously incorporated by reference. The data structure 2800 of the language-neutral representation is depicted in FIG. 28. The data structure 2800 comprises a Source Code Interface (SCI) model 2802, an SCI package 2804, an SCI class 2806, and an SCI member 2808. The SCI model 2802 is the source code organized into packages. The SCI model 2802 corresponds to a directory for the software project 112 being developed by the user, and the SCI package 2804 corresponds to a subdirectory. As is well known in object-oriented programming, the class 306 is a category of objects which describes a group of objects with similar properties (attributes), common behavior (operations or methods), common relationships to other objects, and common semantics. The members 2808 comprise attributes and/or operations.
For example, the data structure 3000 for the source code 2900 shown in FIG. 29 is depicted in FIG. 30. UserInterface 2902 is defined as a package 2904. Accordingly, UserInterface 2902 is contained in SCI package 3002. Similarly, Bank 2906, which is defined as a class 2908, is contained in SCI class 3004, and Name 2910 and Assets 2912, which are defined as attributes (strings 2914), are contained in SCI members 3006. Since these elements are in the same project, all are linked and can be accessed by the software development tool. The data structure 3000 also identifies the language in which the source code is written 3008, e.g., Java.TM. programming language. The software development tool's utilization of the TMM to produce a customized design model and corresponding source code for a selected pattern is explained below with reference to FIG. 31.
The software development tool 110 hosts a substantial number of pattern definitions, including patterns attributable to the four software visionaries known as the "Gang of Four" (Erich Gamma, Richard Helm, John Vlissides, and Ralph Johnson) who published a popular authoritative text on design patterns. The Gang of Four patterns identified herein are more clearly described in Gamma, Erich, et al., Design Patterns: Elements of Reusable Object-Oriented Software, Addison-Wesley (1995), which is incorporated herein by reference. One skilled in the art will appreciate that the pattern generation performed by the improved software development tool is not limited to the Gang of Four patterns, but may also be used with other patterns.
One of the Gang of Four patterns is the Singleton pattern, which ensures that a class has only one instance and provides a global point of access to it. Therefore, clients (e.g., external classes or objects of classes) access a Singleton instance solely through Singleton's instance operation, which returns the one instance of the class. To illustrate the use of a Singleton pattern, the following problem scenario is given. Two objects of two different classes (i.e., two independent executable sections of code) both access a third object having an operation responsible to play an audio clip, the resulting sound is confusing as the two different audio clips are effectively played at the same time. Use of a Singleton class for the third class in this scenario prevents this problem from occurring. Because there is only one instance of the Singleton class for an object to call, only one of the two class objects can access the single instance of the Singleton class to play an audio clip at a given time. The components and variations of the Singleton pattern will be further explained below.
Turning to FIG. 2, an exemplary method in a data processing system for generating software code based on a pattern in accordance with the present invention is shown. To create an instance of a pattern in the software code, the software development tool 110 first receives an element type to distinguish the type of pattern that is to be created (step 202). The element type can be a class, a link, or any known object-oriented component (e.g., method or attribute) from which a new pattern instance can be created. A link is generally a structural relationship between classes, such as a single or bi-directional association, or an aggregation.
In one implementation, depicted in FIG. 3, the software development tool receives a selected element type (e.g., class) and is prompted to generate a pattern based on the selected element type by the activation of a respective radio button 302 on an exemplary GUI interface or screen 300. One skilled in the art will appreciate that any known programming technique for inputting data could be used to convey the same information to the software development tool. Screen 300 shows an empty graphical editor pane 304 and an empty source code editor pane 306 to illustrate a newly opened project 112 that does not yet contain any software code. Therefore, the TMM 114 will have an empty data structure 2800 until invoked by the software development tool to generate a pattern instance.
Referring back to FIG. 2, in response to the prompt to generate a pattern instance, the software development tool displays a list of pattern options that are applicable to the selected element type (step 204) and from which the developer can choose. An exemplary list of pattern options 402 that are applicable to generating a pattern based on class element type 302 is shown in FIG. 4. Examples of the well-known pattern options that may be applied to a class are also identified in Table 1 and Table 2 below with their respective definitions.
TABLE 1
Gang of Four Patterns For A Class
Pattern
Name Pattern Description Pattern Participant & Role
Abstract Provides an interface for Abstract factory
Factory creating families of related or .cndot. declares an interface
for operations that
dependent objects without create Abstract product objects.
specifying their specific .cndot. this participant cannot be
read-only.
classes. Abstract product
Use abstract factory pattern .cndot. declares an interface
for a type of
when Product object.
.cndot. a system should be Concrete factory
independent of how its .cndot. implements the operations
to create
products are created, Concrete product objects.
composed, and .cndot. this participant cannot be
read-only.
represented. .cndot. this participant cannot be
an interface.
.cndot. a system should be Concrete product
configured with one of .cndot. defines a product object
to be created
multiple families of by the corresponding concrete
factory.
products. .cndot. implements the Abstract
product
.cndot. a family of related interface.
product objects is .cndot. this participant cannot be
read-only.
designed to be used .cndot. this participant cannot be
an interface.
together, and you need to
enforce their constraint.
.cndot. you want to provide a
class library of products,
and you want to reveal
just their interfaces, not
their implementations.
Adapter Convert the interface of a class Target
pattern into another interface client .cndot. defines the
domain-specific interface.
expects. Adapter lets classes .cndot. This participant cannot
be a class if the
work together that couldn't class adapter (see below) version
is
otherwise because of chosen.
incompatible interfaces. Adaptee
There are two variations of the .cndot. defines an existing
interface that needs
adapter pattern: object adapter adapting.
and class adapter: Adapter
Use adapter pattern when .cndot. adapts the interface of
adaptee to the
.cndot. you want to use an target interface.
existing class, and its .cndot. this participant cannot be
an interface.
interface does not match .cndot. this participant cannot be
read-only.
the one you need.
.cndot. you want to create a
reusable class that
cooperates with unrelated
or unforeseen classes, that
is, classes that don't
necessarily have
compatible interfaces.
.cndot. (object adapter only) you
need to use several
existing subclasses, but
it's impractical to adapt
their interface by
subclassing every one. An
object adapter can adapt
the interface of its parent
class.
Chain of Avoid coupling the sender of a Handler
Responsibility request to its receiver by .cndot. defines an interface for
handling
pattern giving more than one object a requests.
chance to handle the request. .cndot. implements the
successor link.
Chain the receiving objects .cndot. this participant cannot
be read-only.
and pass the request along the .cndot. this participant
cannot be an interface.
chain until an object handles it. Concrete handler
Use Chain of Responsibility .cndot. handles requests it is
responsible for.
when .cndot. can access its successor.
.cndot. more than one object may .cndot. if the Concrete
Handler can handle the
handle a request, and the request, it does so; otherwise it
handler isn't known a forwards the requests to its
successor.
priori. The handler
should be ascertained
automatically.
.cndot. you want to issue a
request to one of several
objects without specifying
the receiver explicitly.
.cndot. the set of objects that can
handle a request should be
specified dynamically.
Composite Compose objects into tree Component
pattern structures to represent part- .cndot. declares the interface
for objects in the
whole hierarchies. Composite composition.
lets clients treat individual .cndot. Implements default
behavior for the
objects and compositions of interface common to all classes,
as
objects uniformly. appropriate.
Use the Composite when .cndot. Declares an interface for
accessing and
.cndot. you want to represent managing its child components.
part-whole hierarchies of .cndot. (optional) defines an
interface for
objects. accessing a components parent in
the
.cndot. you want clients to be recursive structure, and
implements it if
able to ignore the that's appropriate.
difference between .cndot. This participant cannot be
an interface.
compositions of objects Leaf
and individual objects. .cndot. represents leaf objects in
the
Clients will treat all composition. A leaf has no
children.
objects in the composite .cndot. defines behavior for
primitive objects
structure uniformly. in the composition.
.cndot. this participant cannot be
read-only.
.cndot. this participant cannot be
an interface.
Composite
.cndot. defines behavior for
components
having children.
.cndot. stores child component.
.cndot. implements child-related
operations in
the Component interface.
.cndot. this participant cannot be
read-only.
.cndot. this participant cannot be
an interface.
Decorator Attach additional Component
pattern responsibilities to an object .cndot. defines the interface
for objects that can
dynamically. Decorators have responsibilities added to
them
provide a flexible alternative to dynamically.
subclassing for extending .cndot. this participant cannot be
read-only.
functionality. Concrete component
Use Decorator .cndot. defines an object to which
additional
.cndot. to add responsibilities to responsibilities can be
attached.
individual objects .cndot. this participant cannot be
read-only.
dynamically and Decorator
transparently, that is, .cndot. maintains a reference to a
Component
without affecting other object and defines an interface
that
objects. conforms to Component's interface.
.cndot. for responsibilities that .cndot. this participant
cannot be read-only.
can be withdrawn. .cndot. this participant cannot be
an interface.
.cndot. when extension by Concrete decorator
subclassing is impractical. .cndot. adds responsibilities to
the component.
Sometimes a large number .cndot. this participant cannot be
read-only.
of independent extensions .cndot. this participant cannot be
an interface.
are possible and would
produce an explosion of
subclasses to support
every combination. Or a
class definition may be
hidden or otherwise
unavailable for
subclassing.
Factory Use the Factory Method Product
method pattern when .cndot. defines the interface of
objects the
pattern .cndot. a class can't anticipate factory method creates.
the class of objects it Concrete product
creates. .cndot. implements the Product
interface.
.cndot. a class wants its .cndot. this participant cannot be
read-only.
subclasses to specify the Creator
objects it creates. .cndot. declares the factory
method, which
.cndot. Classes delegate returns an object of type Product.
responsibility to one of Creator may also define a default
several helper subclasses, implementation of the factory
method
and you want to localize that returns a default Concrete
Product
the knowledge of which object.
helper subclass is the .cndot. may call the factory
method to create a
delegate. Product object.
.cndot. this participant cannot be
read-only.
Concrete creator
.cndot. overrides the factory
method to return
an instance of a Concrete Product.
.cndot. this participant cannot be
read-only.
.cndot. this participant cannot be
an interface.
Observer Define a one-to-many Subject
pattern dependency between objects so .cndot. knows its observers.
Any number of
that when one object changes Observer objects may observe a
state, all its dependents are subject.
notified and updated .cndot. provides an interface for
attaching and
automatically. detaching Observer objects.
Use the Observer pattern in .cndot. this participant cannot
be read-only.
any of the following situations: Observer
.cndot. When an abstraction has .cndot. defines an updating
interface for
two aspects, one objects that should be notified of
dependent on the other. changes in a subject.
Encapsulating these .cndot. this participant cannot be
read-only.
aspects in separate objects ConcreteSubject
lets you vary and reuse .cndot. stores state of interest
to
them independently. ConcreteObserver objects.
.cndot. When a change to one .cndot. sends a notification to
its observers
object requires changing when its state changes.
others, and you don't .cndot. this participant cannot be
read-only.
know how many objects .cndot. this participant cannot be
an interface.
need to be changed. ConcreteObserver
.cndot. When an object should be .cndot. maintains a
reference to a
able to notify other objects ConcreteSubject object.
without making .cndot. stores state that should
stay consistent
assumptions about who with the subjects.
these objects are. In other .cndot. implements the Observer
updating
words, you don't want interface to keep its state
consistent
these objects tightly with the subjects.
coupled. .cndot. this participant cannot be
read-only.
Proxy pattern Provide a surrogate or Proxy
placeholder for another object .cndot. maintains a reference
that lets the proxy
to control access to it. access the real subject. Proxy may
Proxy is applicable whenever refer to a Subject if the
RealSubject and
there is a need for a more Subject interfaces are the same.
versatile or sophisticated .cndot. provides an interface
identical to
reference to an object than a Subject's so that a proxy can
be
simple pointer. substituted for the real subject.
.cndot. controls access to the
real subject and
may be responsible for creating
and
deleting it.
.cndot. other responsibilities
depend on the
kind of proxy:
.cndot. remote proxies are
responsible for
encoding a request and its
arguments
and for sending the encoded
request
to the real subject in a different
address space.
.cndot. virtual proxies may cache
additional
information about the real subject
so
they can postpone accessing it.
.cndot. protection proxies check
that the
caller has the access permission
required to perform a request.
.cndot. this participant cannot be
read-only.
.cndot. this participant cannot be
an interface.
Subject
.cndot. defines the common
interface for
RealSubject and Proxy so that a
Proxy
can be used anywhere a RealSubject
is
expected.
.cndot. this participant cannot be
read-only.
RealSubject
.cndot. defines the real object
that the proxy
represents.
.cndot. this participant cannot be
read-only.
Singleton Ensure a class only has one Singleton
pattern instance, and provide a global .cndot. a class, which should
be instantiated
point of access to it. only once.
Use the Singleton pattern when .cndot. this participant
cannot be an interface.
.cndot. there must be exactly one Singleton Factory
instance of a class, and it .cndot. a class with a static
method to
must be accessible to instantiate Singleton.
clients from a well-known .cndot. this participant cannot be
read-only.
access point. .cndot. this participant cannot be
an interface.
.cndot. when the sole instance The Singleton and Singleton
Factory
should be extensible by could be the same class. In this
case, it
subclassing, and clients will contain a static method to
instantiate
should be able to use an itself only once.
extended instance without
modifying their code.
State pattern Allow an object to alter its Context
behavior when its internal .cndot. defines the interface of
interest to
states change. The object will clients.
appear to change its class. .cndot. maintains an instance of
a
Use the State pattern in either ConcreteState subclass that
defines the
of the following cases: current state.
.cndot. An object's behavior .cndot. this participant cannot
be read-only.
depends on its state, and it .cndot. this participant cannot
be an interface.
must change its behavior State
at runtime depending on .cndot. defines an interface for
encapsulating
that state. the behavior associated with a
.cndot. Operations have large, particular state of the
Context.
multipart conditional .cndot. this participant cannot be
read-only.
statements that depend on ConcreteState
the object's state. This .cndot. each ConcreteState
implements a
state is usually represented behavior associated with a state
of the
by one or more context.
enumerated constants. .cndot. this participant cannot be
read-only.
Often, several operations
will contain this same
conditional structure. The
State pattern puts each
branch of the conditional
in a separate class. This
lets you treat the object's
state as an object in its
own right that can vary
independently from other
objects.
Visitor pattern Represent an operation to be Visitor
performed on the elements of .cndot. declares a Visit
operation for each class
an object structure. Visitor lets of ConcreteElement in the
object
you define a new operation structure. The operation's name
and
without changing the classes of signature identifies the
class that sends
the elements on which it the Visit request to the Visitor.
That
operates. lets the Visitor determine the
concrete
Use the Visitor pattern when class of the element being
visited.
an object structure contains Then the Visitor can access the
element
many classes of objects with directly through its particular
interface.
differing interfaces, and you .cndot. this participant cannot
be read-only.
want to perform operations on Visitor Adapter
these objects that depend on .cndot. provides trivial
implementation for
their concrete classes. Many each Visitor's operation.
distinct and unrelated .cndot. this participant cannot be
read-only.
operations need to be .cndot. this participant cannot be
an interface.
performed on objects in an Concrete Visitor
object structure, and you want .cndot. implements each
operation declared by
to avoid "polluting" their Visitor. Each operation implements
a
classes with these operations. fragment of the algorithm
defined for
Visitor lets you keep related the corresponding class of
object in the
operations together by defining structure. Concrete Visitor
provides
them in one class. When the the context for the algorithm and
stores
object structure is shared by its local state. This state
often
many applications; use Visitor accumulates results during the
traversal
to put operations in just those of the structure.
applications that need them. .cndot. this participant cannot
be read-only.
The classes defining the object .cndot. this participant
cannot be an interface.
structure rarely change, but Element
you often want to define new .cndot. defines an accept
operation that takes a
operations over the structure. visitor as an argument.
Changing the object structure Concrete Element
classes requires redefining the .cndot. implements an accept
operation that
interface to all visitors, which takes a Visitor as an
argument.
is potentially costly. If the .cndot. this participant cannot
be read-only.
object structure classes change .cndot. this participant
cannot be an interface.
often, then it's probably better
to define the operations in
those classes.
TABLE 2
Additional Patterns To Be Applied To A Class
Pattern Name Pattern Description Pattern Participant & Role
Bean pattern This pattern can be used to Single Bean Class
modify existing class or to For each property the pattern
creates an
create a new public class so that attribute (its visibility
is controlled by
it will contain user-specified the "Set visibility" option)
used to store
bean properties. the property value. Such
attributes are
initialized in the constructor.
The "Generate get methods" and
"Generate set methods" options
control
whether to create "get" or "set"
accessors to the created
properties.
JavaServer This pattern can be used to
Pages Pattern generate JavaServer Page
content file to display properties
of beans. To take full advantage
of this pattern, you must have
the beans to display in your
JSP-capable webserver
classpath.
Description A catalog-entry-like Typical Attributes
Archetype description. A collection of .cndot. type-unique number,
code or name
values that apply again and for the type of objects
described,
again. Provides behavior across e.g. Power Pick Up.
the collection of all things that .cndot. Description-text
description of the
correspond to its description. type of objects described,
e.g. Long
For example, your red pickup is wheelbase, large engine.
a vehicle; it's a thing with its .cndot.
itemNumber-analogous to a
own serial number (called a catalog entry number.
vehicle identification number), .cndot.
defaultValue-contains default
purchase date, color, and value for an attribute in a
odometer reading. The corresponding PartyPlaceThing,
corresponding catalog-entry- Role or MomentInterval.
like description is vehicle Typical Methods
description; it establishes Descriptions often include
methods like
manufacturer, model number, how many are available and
calculate
date of manufacture, and total for quantity. Use a
plug-in point
available colors; it also is a when it has algorithmically
complex
good place to locate business- behavior and we want the
option of
related methods like, "how plugging in an alternative
behavior at
many of these trucks are in times.
good working order?" .cndot. findAvailable-locate a
PartyPlaceThing that is
available
(to play a particular Role in a
particular MomentInterval).
.cndot. calcQtyAvailable-count
the
PartyPlaceThings available (to
play
a particular Role in a
particular
MomentInterval).
.cndot. defaultAlgorithm-some
sort of
calculation.
.cndot.
invokePlugInElseDefaultAlgorithm-
if plugin supplied then invoke
it
or else invoke the
defaultAlgorithm.
MomentInterval Represents something that Typical Attributes
Archetype needs to be worked with and .cndot. number-unique
identifying
tracked for business or legal number used by external
entities to
reasons that occurs at a moment reference a specific
instance of the
in time, or over an interval of class.
time. Either a moment or an .cndot.
dateOrDateTimeOrInterval-time
interval of importance in the of moment or duration of
interval.
problem domain. A sale is .cndot. priority-e.g., high,
normal, low.
made at a moment in time, the .cndot. total-cached result
from a
date and time of that sale. A calcTotal method (for
performance
rental happens over an interval to prevent necessary
iteration across
of time, from checkout to MI's).
check-in. A reservation occurs .cndot. status-e.g., for a
LoanApplication
over an interval of time, from one of New, Submitted,
Approved,
the time that it is made until the Rejected, etc.
time it is used, canceled, or Typical Methods
expires. A sale could even be .cndot.
makeMomentInterval-supports the
an interval of time, if you track business process for
making one,
the duration of the sale for that is.
performance assessments. .cndot. addDetail-adds details
(parts).
What's important is that it is one .cndot.
calcTotal-interacts with its parts
of these two, not which one of to calculate its total.
the two it is. .cndot. recalcTotal-recalculates
its total
(forcing a recalculation,
regardless
of any internally buffered
value).
.cndot. complete-complete the
MomentInterval.
.cndot. cancel-cancel the
MomentInterval.
.cndot. mi_generateNext-generate
next
(subsequent) MomentInterval.
.cndot. mi_assessWRTPrior-assess
with
respect to prior
moment-intervals.
.cndot.
mi_assessWRTSubsequent-assess
with respect to subsequent
moment-
intervals.
.cndot. mi_comparePlanVsActual-
compare MI's representing the
planned with MI's representing
the
actual.
.cndot.
listMomentIntervals-class/static
method: list all of the moment-
interval objects.
.cndot. calcAvgMomentInterval-
class/static method: calculate
the
average moment-interval (usually
average amount, although it
could
be something like average weight
or
average fulfillment time).
PartyPlaceThing A party (meaning, a person or Typical Attributes
Archetype an organization), place or thing .cndot.
serialNumber-uniquely identifies
is someone or something who an instance of this class,
e.g.,
plays different roles. A person vehicle identification
number,
might be both an employee and social security number.
a customer. A place might be .cndot. address-contact
information:
both a retail outlet and a postal address, e-mail address,
wholesale outlet. A thing might phone numbers.
play a role in a manufacturing .cndot. customValue-values
differing
process and a different role in a from the default for this
type of
purchasing process. Things object (defaults in
corresponding
often act as containers for other Description).
objects and usually include Typical Methods
methods like assess .cndot. isAvailable-determines
if it's
performance or assess value. currently available (checking
status
or interacting with its Roles).
.cndot.
getCustomElseDefaultValue-gets
its custom value or if not
present
asks its corresponding
Description
for its default value.
.cndot.
assessValueToBusiness-assesses
its value to the business (by
interacting with its yellow
roles).
.cndot.
assessPerformance-assesses its
performance (by interacting with
its
yellow roles).
Role archetype Role is a way of participation Typical Attributes
by a party (person or .cndot. status
organization), place or thing. Typical Methods
Many times persons or .cndot. assessAcrossMIs
organizations are eligible to .cndot. listMI
play the same role (for example, .cndot. listRoles
owner) within a problem .cndot. assessAcrossRoles
domain that we are working in.
So we model the role-player (a
party, place, or thing) as well as
the role (the "hat" that the party,
place, or thing is wearing). The
role player captures core
attributes and behaviors that
apply no matter what
combination of hats it might be
wearing. For person, that often
includes attributes like legal
name and date of birth. It also
includes methods that enforce
business rules across the
collection of roles being played,
for example, a method
"authorized for" that interacts
with each role and applies rules
across that collection of roles to
determine if it is authorized to
take a given action. Party,
person, and organization roles
are the norm. Occasionally
you'll find place and thing roles
too (for example, a product and
its two roles, "product in a sales
process" and "product in use").
Class Stub This useful pattern can be
implementation applied to a class in order to
pattern create stubs for all the methods
found in interfaces (and their
parent interfaces) this class
implements. If a class extends
another class, then this pattern
creates stubs for all the
constructors found in the
superclass. These constructor
stubs simply call the
corresponding constructors in
the superclass.
The software development tool also provides an option to display all pattern options prior to receiving a selected element type. After a pattern selection is made in this implementation, the software development tool may prompt the developer for information regarding the element type necessary to implement an instance of the selected pattern for the developer's current software development project, i.e., to generate the corresponding code.
The software development tool receives a pattern selected by the developer 206. Based on the pattern selected by the developer, the software development tool determines whether the pattern has configurable features (step 208) and, if so, displays them for the developer to complete or modify (step 210). A configurable feature defines a variation of the pattern. A configurable feature is a property or a parameter of the pattern that a developer can modify or select to tailor the pattern that is created. A configurable property may be an identification of a role for a pattern participant, or an attribute or method associated with a pattern participant. To adhere to the definition of the selected pattern, the software development tool uses default entries for configurable properties to complete or generate the pattern instance when the developer does not provide any modifications. Parameter options control whether a feature of a selected pattern definition is to be applied in generating the selected pattern instance as explained below.
As depicted in FIG. 4, in response to the selection of a Singleton pattern 404, the exemplary parameterization dialog box 405 displays configurable properties 410 and parameters 420. Singleton configurable properties 410 include: a name for a Singleton class 411 to be generated, a name for a Singleton factory 412 which has a static method to instantiate Singleton (this property causes a variation in how the Singleton pattern is applied, as explained below), the name of the unique instance attribute or variable 413 that refers to the one instance of the class to be utilized by other objects, and the name of the instance method or operation 414 to access and return a reference to the unique instance attribute 413 (e.g., returns a reference to Singleton object for this example). One skilled in the art will appreciate that configurable properties 410 correspond to various elements used for generating the selected pattern.
Singleton parameters 420 include "Generate thread safe code" option 421, and "Create pattern links" option 422. "Generate thread safe code" option 421, when selected, ensures that the pattern (e.g., Singleton) object behaves correctly in a multi-threaded environment by using a synchronized block in the instance method 414. A thread is a path of execution, and a program may have more than one thread. A synchronized block is a Java construct that prevents a simultaneous access of a block of code by multiple threads. The "Create pattern links" option 422, when selected, generates pattern information (e.g., see FIG. 9, Singleton pattern information 912), such as dependency links that identify relationships between classes and interfaces participating in the pattern. Pattern information is embedded in a comment field associated with a respective pattern element or participant so that a pattern instance can later be easily identified in the corresponding source code. Embedding pattern information will be further described below.
Other parameters, depicted on screen 500 in FIG. 5, which may be displayed (depending on the design of the selected pattern) include: "Copy documentation" 522, "Initialization variant" 524, and "Version" 526. Copy documentation 522 controls whether to copy comments from methods in interfaces participating in the pattern to the stubs of these methods made by the pattern in classes implementing such interfaces. Initialization variant 524 defines the kind of initialization for an attribute of a pattern participant. For example, in the previously introduced adapter pattern, the adapter class has an attribute 525 that is initialized based on a call from a "set method" or based on a "constructor parameter" for an object of the adapter depending on the selection for the Initialization variant 524. Version 526 defines whether an object or a class variation of a selected pattern is to be generated.
Additional parameters, depicted on screen 600 in FIG. 6, which are primarily for generating a Java Bean instance include "Generate get methods" 622, "Generate set methods" 624, "Create default constructor" 626, and "Set visibility" 628. A Java Bean is a software component built using the Java.TM. programming language that is designed to be used in Java programs and manipulated in a Java Graphical User Interface (GUI) builder tool. In general, the software component is a self-contained group of software elements that can be controlled dynamically and assembled to form applications by the Java GUI builder tool. A Java Bean is more clearly described in Robert Englander, Developing Java Beans, O'Reilly (1997). Generate get methods 622 and Generate set methods 624 control whether to create "get" or "set" accessor methods for a specified property 612 in a Java Bean pattern. Create default constructor 626 controls whether the software development tool automatically creates a constructor to initialize an attribute or variable for the specified property. Set visibility 628 controls whether the attribute for the specified property 612 is privately accessible, protected but capable of being accessed by a subclass, locally accessible to objects in the same package, or publicly accessible. As is well known in object-oriented programming, a package is a library of classes grouped together based on common functionality, like performing I/O.
Returning to FIG. 2, after displaying the selected pattern's configurable properties and parameters in step 210, the software development tool determines whether a special pattern property needs to be defined (step 212) and, if necessary, receives the special pattern property prior to generating the selected pattern instance (step 214). A special pattern property is a property that the software development tool expects the developer to provide because the software development tool cannot deduce a default entry. As depicted on screen 700 in FIG. 7, a special pattern property is defined for generating an abstract factory pattern instance. In this example, the special pattern property for this pattern, which the software development tool asks to be defined, is the identification of a concrete product (see message 702). The yet to be identified concrete product will implement the interface of abstract product 714 and will have its objects created by concrete factory 716. In this example, the developer is prompted on another screen for the name of an existing class element or a new class element to be created as part of the pattern that will fulfill the role of the concrete product.
As shown in FIG. 2, if a developer makes any entries or modifications (i.e., variations from default values) to the selected pattern's configurable parameters or properties, the software development tool receives the variations (step 216) and determines whether the selected pattern with the variations can be applied to the selected element (step 218). To determine whether the variation is suitable, the software development tool checks the variation for syntax errors and for semantic errors such as a duplicate name for two properties that need to remain unique. In addition, the software development tool will check the selected pattern with the variation for completeness. For, example, screen 800 illustrates that a variation of removing and not replacing the default entry or identification for the Singleton factory 412 is not permitted (see message 802). The Singleton pattern cannot be generated unless the Singleton Factory 412 property or role is supplied by the developer to complete the pattern.
As shown on screen 400 in FIG. 4, Singleton 411 and Singleton Factory 412 have the same value, which results in a single class having a method to instantiate itself only once as shown in FIG. 9. Singleton Factory 412, however, may be given a different value (e.g., the name Singleton Factory) which results in a variation in the Singleton pattern instance that is generated as illustrated in FIGS. 10 and 11. Thus, each pattern has a plurality of variations based on configurable properties and parameters associated with each pattern.
If the selected pattern does not have any configurable properties, then the software development tool determines the software language in which the pattern is to be generated (step 220) For example, standard programming policy for the developer's company may fix properties for a pattern like the "stub implementation" pattern. When a selected pattern instance is to be applied to a new project, the software development tool references a language variable associated with the new project to identify the default software language to use in generating the selected pattern instance. For instance, the language variable may identify the software language to be the Java.TM. programming language or C++. Similarly, the software development tool references a path variable associated with the new project to identify the location to store the new pattern instance (step 221). In one implementation, both the language variable and path variable may be accessed and modified by a developer.
Once the applicable software language has been identified, the software development tool generates source code corresponding to the selected pattern and received variations (step 222). FIG. 31 depicts a flow chart illustrating an exemplary process performed by the software development tool to produce pattern code. Initially, the software development tool determines whether the participant has already been found in the source code for the project 112 (step 3102). Because the software development tool is generating a new instance of the selected pattern for the project 112, the TMM 114 data structure is empty or does not yet contain code corresponding to a participant in the pattern. Consequently, the software development tool invokes the TMM 114 to add an element to the project 112 corresponding to a participant type to be created, such as a class for the Singleton participant (step 3104). The software development tool next determines whether the element now identified as a pattern participant has constructors for operations or attributes associated with the pattern participant (step 3106). As described below in context with applying a pattern to an element within existing code, the software development tool invokes the TMM to match attributes, operations, and operation statements in an element that has been identified as a pattern participant and that has at least some constructors associated with the pattern (step 3108). When generating a new pattern instance, the element that is added as a pattern participant does not yet contain any constructors so the software development tool invokes the TMM to add attributes, operations, and operation statements to the newly added element that correspond to the role of the participant (step 3110). Finally, the software development tool determines whether the pattern has another participant for which the steps 3102-3110 need to be repeated (step 3112).
In FIG. 9, the exemplary screen 900 shows the source code 902 generated in response to the selected Singleton pattern of FIG. 4 with the variation that Singleton 411 and Singleton Factory 412 have the same value (i.e., attributes and operations of these two pattern participants are assigned to the same class element). The single class diagram 920 graphically reflects the generation of the selected Singleton pattern with the same variation. In FIGS. 10 and 11, the screens 1000 and 1100 illustrate the source code 1002 and source code 1102 generated in response to the selected Singleton pattern with the variation that Singleton 411 and Singleton Factory 412 have different values (e.g., participants given same name as the respective property or role). In this scenario, the attributes and operations 1104 for the Singleton pattern have been automatically generated in association with the source code 1102 for Singleton Factory class 1106. The class diagrams 1022 and 1024 graphically reflect the generation of the selected Singleton pattern with this variation.
Finally, as previously mentioned, pattern identification information is retained automatically by storing the identification information for the selected pattern in a comment associated with the generated software code based on the selected pattern (step 224). Returning to FIGS. 9 and 10, the pattern identification information 912 and 1012 identify the pattern, the role of a supplier of the class instance (Singleton Factory), and the name of the supplier participant playing the role (Singleton in FIG. 9, and Singleton Factory in FIG. 10).
Because the pattern information is embedded in source code comments, documentation generation and future modifications or improvements to a program for a project can be facilitated as the pattern within the code is made recognizable. As explained below, the software development tool can automatically detect undesirable code and transform it to improved code corresponding to a selected pattern. By embedding pattern information in source code comments, the generated pattern can later be identified as undesirable code, which can be easily located from among all other code in a program.
For example, a developer may utilize a Singleton pattern to ensure that only one instance of a class is created when the code for a particular project is compiled and executed. While this may have been a good design decision at the time, there may be reasons to improve the design, like improving the performance of the code which lead the developer to identify the Singleton as a bad pattern for the code. Applying another pattern or an improved version of the Singleton pattern to replace the originally generated pattern is supported by the software development tool as explained in context with "Applying A Pattern To Existing Code," below.
The software development tool is not limited to generating a pattern based on a selected class element type. For example, screen 1200 in FIG. 12 depicts an exemplary GUI screen for initiating the generation of a link pattern and for identifying the two nodes (a node may be a class or an interface) between which the software development tool will generate a selected link pattern. In this implementation, the software development tool receives a link element type and is prompted to generate a pattern for the selected element type based on the actuation of a respective radio button 1202 and by the identification of the node 1210, SingletonFactory class, and the node 1220, Class 1.
To generate a link pattern, the software development tool 110 performs the process steps shown in FIG. 2 and described above. FIG. 13 depicts a screen 1300 that shows an exemplary list of pattern options 1302 that the software development tool may generate based on a link element type, and the configurable properties 1311 and 1312 that the software development tool may use to generate the selected "Association as Vector" link pattern 1304. Screen 1400 in FIG. 14 depicts an exemplary screen showing the source code 1402 generated by the software development tool in response to the selected "Association as Vector" pattern of FIG. 13. As illustrated in FIG. 14, the software development tool embeds pattern information 1404 in a comment associated with the source code 1402, which as mentioned advantageously supports documentation of the project and later detection of the pattern in the code.
Applying a Pattern To Existing Code
Applying a pattern to existing code involves generating a pattern instance that replaces in whole or in part a portion of software code for a project, while not altering the external behavior of the remaining software code. Thus, applying a pattern extends the concept of refactoring to improve the design of software after the design has already been coded or written. By utilizing the software development tool to apply a pattern to existing software as described below, a problem in existing software code can be reworked to conform to a solution described with respect to the pattern definition.
FIGS. 15a and 15b depict a flow diagram of an exemplary process that the software development tool performs to apply a pattern to existing code. Initially, the software development tool receives an indication of a selected element within the existing code that is to be transformed as a result of applying the pattern (step 1502). The selected element can be a class, a link, or any known object-oriented component (e.g., method or attribute) that may be a participant or identify a relationship in a pattern to be applied.
In one implementation, the software development tool receives the indication of the selected element in response to a developer selecting the graphical notation of the selected element in the graphical editor pane 304. In the example depicted in FIG. 16, screen 1600 shows that the diagram 1602 corresponding to the "CashSaleDetail" class element has been selected. The "CashSaleDetail" class element is a portion of the existing code for a CashSales project 112 that has been read into the TMM 114 data structure 2800 and that is represented graphically by "CashSale" class symbol 1620, "IMakeCashSale" interface symbol 1630, "ProductDesc" class symbol 1640, "ProductPrice" class symbol 1650, and "InsuffPaymentException" class symbol 1660. While the "CashSaleDetail" class element is not in view on source code editor pane 306, the constructor method element "CashSaleDetail (ProductDesc prod)" 1602 which is a defined operation within the "CashSaleDetail" class is in view on the source code editor pane 306, indicating that "CashSaleDetail" class element has been selected. The software development tool may also receive the indication of the selected element to apply a pattern in response to the developer identifying the selected element in the source code editor pane 306.
As shown in FIG. 15a, the software development tool also receives from the developer an indication that a pattern is to be applied to the selected element (step 1504). The indication to apply a pattern to the selected element may be conveyed in response to the developer choosing a respective option from a pull-down menu or from a speed menu that appears when a button on a mouse is actuated while an associated cursor is over the selected element. One skilled in the art will appreciate that any known programming technique for inputting data could be used to convey the same information (i.e., the selected element and the indication to apply a pattern) to the software development tool.
In response to receiving the indication of the selected element and the indication to apply a pattern, the software development tool determines the suitable patterns that may be applied to the selected element (step 1506). The software development tool determines which patterns are suitable based on the type of selected element, such as a class as opposed to a link or a member. To determine suitability, the software development tool checks if a participant in a respective pattern uses the type of selected element. The example shown in FIG. 17 indicates that the Singleton option 1702 has been selected. This corresponds to the software development tool identifying that a Singleton pattern uses an element of type "class." To further illustrate the software development tool analysis of whether a pattern is suitable for applying to a selected element assume that the developer had actually chosen the "IMakeCashSale" interface symbol 1630 as the selected element to apply a pattern. In this example, the software development tool determines that the Singleton pattern uses a class participant that has a static variable that refers to the one instance that is created for the class. The method for creating the one instance of a Singleton and the variable that then refers to the one instance of the class may be delegated to a SingletonFactory class but not an interface. Therefore, the software development tool determines that a Singleton pattern cannot be applied to the selected interface element and the Singleton pattern would not be listed as an option in this example. One skilled in the art will appreciate that a similar analysis could be performed for any pre-defined pattern that has known participants with known roles as previously described.
The software development tool then displays the suitable patterns from which the developer can choose (step 1508). FIG. 17 depicts an exemplary screen 1700 that shows a list of pattern options 1704 that the software development tool may apply based on the selected element CashSaleDetail being a class element type. Example pattern options that may be applied to a class are reflected in the list 1704 with their respective descriptions, and are presented in Table 1 herein. Similarly, FIG. 24 depicts an exemplary screen 2400 that shows a list of pattern options 2404 that the software development tool may apply to the selected element 1670 between CashSaleDetail 1610 and ProductDesc 1640, which are of the link element type.
The software development tool next receives an indication of a selected pattern option (step 1510) from among the pattern options displayed, and determines whether the associated selected pattern has more than one participant (step 1514). In the event that the selected pattern has more than one participant related to an additional element, the software development tool performs a heuristic to determine whether there is another related element in the existing code that is suited to be the additional element, i.e., that is suited to play the role associated with the different pattern participant (step 1516). To determine whether another related element is suited to play the different role in the selected pattern, the software development tool performs the heuristic of locating pattern identification information in a comment associated with the selected element 1610 or associated with other related elements 1620, 1630, 1640, 1650, or 1660. As shown in FIG. 21, identification information 2110 identifies the construct for the related class element "CashSaleDetailFactory" in the comment associated with a Singleton pattern. In this example, the software development tool then knows to search within the existing code for a class element with the name "CashSaleDetailFactory" that may already be suited for playing the role of Singleton Factory.
The software development tool may also utilize a heuristic that combines checking the existing code for common pattern naming conventions of pattern participants (e.g., a class having a name which is or includes "Singleton Factory") with searching the existing code for constructs in other related elements that show the implementation of pattern properties and pattern functions that reflect the role of the different pattern participant. For example, when applying the Singleton pattern, the software development tool will look in the existing code for a class element that has the Singleton pattern attribute of "instance" matched with a "get" function having the same return type of instance. Both are found in the CashSalesDetailFactory class element 2202. Thus, the software development tool would have identified this class to fulfill the different role for the Singleton pattern.
In the event the software development tool does not identify another element that is suitable to play a role of the different pattern participant, the software development tool provides a missing participant needed to complete the selected pattern option (step 1518). After providing the missing participants, or if the pattern does not have more than one participant, the software development tool 110 displays the pattern participants (e.g., 1715 and 1716) and their roles (e.g., 1711 and 1712, respectively) (step 1520). Providing a missing participant includes adding a new software element to the existing code, as explained below in relation to FIGS. 21 and 22.
In addition to displaying the pattern participants and their roles in step 1520, the software development tool also displays a recommended role 1730 for the selected element based on the pattern and the other related elements that were found to be suitable to play a role in the pattern as described above. Because the Singleton pattern can be implemented with only one class, the example depicted in FIG. 17 shows that the selected element (CashSaleDetail class) is assigned the roles of both Singleton 1711 and Singleton Factory 1712. The example depicted on screen 2300 in FIG. 23 shows that the software development tool will provide a recommendation (e.g., subject 2302) for the role of the selected element in a pattern that necessarily has multiple participants (e.g., observer participants 2310) as well, such as for the Observer pattern (a pattern that specifies that an Observer object be notified of a state change of a Subject object).
The software development tool also determines whether the selected pattern has configurable features (step 1522) and displays them (step 1524) for a developer to change in order to vary the application of the pattern as described previously for generating a pattern instance. Configurable features for a pattern include configurable properties 1710 and parameters 1720. As shown in FIG. 17, a role for a pattern participant is a property of the pattern so the software development tool allows roles (e.g., Singleton 1711 and Singleton factory 1712) to be reassigned by the developer to related elements in the existing code. Upon receiving a variation to configurable properties 1710 (including participants and roles) and parameters 1720 (step 1526), the software development tool checks the variation for syntax and semantic errors based on the selected pattern (step 1528), and determines whether the selected pattern with the variation can be applied (e.g., can't enter the name of an interface to be assigned the role of Singleton 1711 or Singleton factory 1712 as previously discussed) (step 1530).
If the selected pattern can be applied, the software development tool determines the software language in which the pattern is to be generated (step 1532) and the location where the transformed source code is to be stored (step 1533). Because the software development tool is applying a pattern to existing software code, the software development tool references the extension of the filename associated with the existing software code to be modified to ascertain the language for applying the selected pattern. For example, Java.TM. code will have a ".java" extension and C++ code will have a ".cpp" extension. The software development tool may also perform these steps in the same manner as previously described for generating a pattern instance by referencing project variables for language in use and for path to store a software code file.
Once the software language is determined, the software development tool transforms the portion of existing software code corresponding to the selected pattern with any received variation (step 1534) and refactors the transformed source code (step 1536). To transform the portion of the existing software code, the software development tool performs the process steps depicted in FIG. 31 as previously described to invoke the TMM 114 to produce the pattern code in the project 112. Transforming the portion of existing software code generally means adding, modifying, or replacing the code in the selected element or in the other related elements that were designated as pattern participants to reflect a role played by a respective pattern participant. Code elements that are added to a participant in the pattern correspond to attributes, methods, or constructs needed to define and implement a role for the participant. Refactoring may comprise changing a reference to the selected element or related element that have become a participant in the applied pattern to an appropriate reference within the pattern.
For example, applying the Singleton pattern variation shown in FIG. 17, the software development tool transforms the selected CashSaleDetail class by adding the attribute "instance" 1802, the method "getInstance" 1902, and the construct "protected" (not shown in source code editor) that is graphically depicted as a "#" addition to the constructor for CashSaleDetail 1922. These elements are added to CashSaleDetail to prevent other objects from creating separate instances of this class. Any other class (e.g., CashSale class graphically depicted as diagram 1830) referencing the CashSaleDetail class (graphically depicted as diagram 1820 on screen 1800 in FIG. 18) calls getInstance 1904 rather than construct an instance of the Singleton, CashSaleDetail, themselves. Hence, as part of applying the Singleton pattern, the software development tool searches the existing code for prior references to the CashSaleDetail class and refactors the prior reference to include a call to the getInstance 1904 method to preserve the one instance of CashSaleDetail class. The pattern identification information is retained by storing the identification information for the selected pattern in a comment associated with the generated software code based on the selected pattern (step 1538).
In another example shown on screens 2000, 2100 and 2200 in FIGS. 20-22, respectively, the software development tool receives a variation in the selected Singleton pattern that calls for the roles of Singleton 1711 and Singleton factory 1712 to be associated with two different participants (i.e., 1715 and 2016). Based on the variation, the software development tool searches the existing code for the participant "CashSaleDetailFactory" 2016, determines that this participant is missing, and generates the source code 2202 for the missing participant 2016.
To complete the application of a pattern to a portion of existing code that includes the selected element, the software development tool generates identification information 1810 and 2110 for the selected pattern 302 in a comment field associated with the existing code such that the pattern can be detected in the existing code. This facilitates the automatic detection of a bad or anti-pattern in order to apply a new pattern as the software development tool can find bad pattern participants by searching the comment fields in the existing code as opposed to searching elements in the existing code for naming conventions or constructs associated with the bad pattern participants. Thus, it is contemplated that in lieu of receiving a selected element to apply a pattern, the software development tool may receive a selected anti-pattern to automatically detect. To detect the anti-pattern, the software development tool may follow one or more detection rules or heuristics as described herein for applying a pattern to a selected element. Thus, the software development tool advantageously will support updating existing code associated with new versions of known patterns (e.g., a new implementation of the Singleton pattern), and deem the older, previously applied pattern as being "bad" and in need of replacement.
Defining A New Pattern From Existing Code
The software development tool may also be used to define and store a new pattern based on a developer's identification of related elements within existing code. FIG. 25 depicts a flow diagram illustrating an exemplary process performed by the software development tool for capturing a user-defined pattern. As one skilled in the art will appreciate, any known programming input mechanism may be used to signal the software development tool that a developer wishes to define a pattern. As shown in FIG. 25, the software development tool receives an identification of one or more selected elements to be pattern participants in the user-defined pattern (step 2502). The developer conveys which elements in the existing code are to be included in the pattern by clicking a mouse button when an associated cursor is over one of the selected elements in the source code pane 306 or when the associated cursor is over the respective graphical notation in the graphical code pane 304. Alternatively, the developer may convey the group of elements to be included in the user-defined pattern by utilizing a known drag and drop feature of a mouse to corral the group of elements textually or graphically.
After an identification of the one or more selected elements to be pattern participants is received, the software development tool creates a copy of the one or more selected elements (step 2504). Each of the one or more selected elements has a coded name and has an associated sub-element, such as an attribute or method. The software development tool next receives an assigned role name for each selected element identified by the developer as a participant in the pattern (step 2506). FIG. 26 depicts an exemplary dialog box 2600 that the software development tool may use to display the user-identified one or more pattern participants and to receive a role name to be assigned to the identified one or more pattern participants. The role name is indicative of the operation that the participant handles within the existing code in relation to the related elements that have been identified as participants in the pattern. The software development tool then locates within the copied portion of the existing code the coded name of each identified one or more pattern participants and replaces the coded name with the respective assigned role name (step 2508). This advantageously allows any subsequent developer to easily utilize this defined pattern where appropriate based on the roles assigned to participants in the pattern.
The software development tool also receives modifications to the one or more selected elements in the copied portion of the existing code (step 2510). In this step the developer may be allowed to modify or remove an operation from the one or more selected elements or identified pattern participants. Thus, sections of the copied portion of the existing code that are not essential to be preserved as part of the pattern can be removed. In addition, the software development tool may receive an indication from the developer identifying sub-elements (e.g., attributes or methods) of the one or more elements that are to be configurable options in the pattern (step 2512). The software development tool may mark or enclose each configurable sub-element with a known identifier (e.g., "^subelement^") that is not part of a construct or operator for the software language associated with the existing code. When the pattern is utilized in future software projects, the software development tool when prompted to apply the defined pattern can easily identify, display, and then receive a variation to the sub-element that the developer indicated would be configurable.
The software development tool then stores the pattern (step 2514) and places the pattern name in the list of other pattern templates (step 2516). The pattern name may be one of the role names assigned by the developer or a name provided by the developer to capture the purpose served by the pattern or the solution that the pattern solves.
While various embodiments of the application have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible that are within the scope of this invention. Accordingly, the invention is not to be restricted except in light of the attached claims and their equivalents.
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- Inventors
Coad, Peter; Charisius, Dietrich; Aptus, Alexander;
- Assignee
Borland Software Corporation (Scotts Valley, CA)
- Published
Feb-1-2005
- Current US Classes:
717/106
717/108
717/109
717/114
717/116
- Application #
680030
- International Classes
G06F 009/44
- Field of Search
717/100 717/103-106 717/108 717/109 717/114 717/116 717/138 717/117 719/315 715/507 715/513 345/473 345/588 706/50 706/48 709/236 382/159
- Examiner
Das; Chameli
- Agent
MacCord Mason PLLC
- US Patent References:
4882756
4956791
5189709
5485569
5699310
5748769
5768590
5860004
5915259
5916305
5946484
5960200
6085035
6122757
6292938
6346945
6459435
6615199
6651108
6651240
6691122
6748588
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