Develop Aspect-Oriented Java Applications with Eclipse and AJDT
By Matt Chapman, Dr. Helen Hawkins2005-05-16
Build configurations
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Some aspects form an integral part of a system, whereas others are used to provide particular features, such as debugging support, that are only required some of the time. Thus, you'll often want to selectively add and remove aspects from an application. AJDT provides this capability using the concept of build configurations, which define the source files within a project that are passed to the compiler. The tools make it easy to work with build configurations by enabling direct manipulation of source files from the Package Explorer within Eclipse. The Spacewar example has a debug aspect that is initially removed from the build configuration. If you look closely at the Package Explorer, as shown in Figure 6, you will see that the icon for Debug.java is hollowed out, indicating its exclusion. Notice also that the icon for the
spacewar package is partially emptied out, to indicate that some, but not all, of the package has been excluded.Figure 6. Package Explorer with excluded resources
You can add the debug aspect to the project simply by right-clicking the Debug.java file and selecting the Include in "demo" configuration menu option. The source and package icons will now fill in, as shown in Figure 7, and the project will be built to include this file (unless Eclipse autobuilding is disabled).
Figure 7. Package Explorer with everything included
If you now run the Spacewar program again, you'll see a new window, with debugging information.
To exclude an aspect, simply right-click the source file again and select the Exclude option. You can also hold down the Shift or Ctrl keys to select multiple source files, or even entire packages, to include or exclude. Changes made in this way affect the current, or active, build configuration, but sometimes it is useful to preserve a particular configuration for later use. This is done by storing build configurations in files with the .ajproperties extension. If you look in the Package Explorer for the Spacewar code, you will see two such files, called demo.ajproperties and debug.ajproperties, as shown in Figure 8. One of the icons has a triangle in it, which indicates that it is the active configuration. Any changes made to the configuration using the Include and Exclude contextual menu options are written to the currently active configuration file.
Figure 8. Build configuration files
To switch to a different build configuration, simply select the appropriate properties file, right-click, and select Activate this configuration from the contextual menu. The project is then rebuilt with the new settings. Another way to switch between build configurations is to select Project>Activate build configuration, which displays a submenu with all of the build configurations that exist for the current project. This submenu also has a Save as... option that allows you to create new build configurations by writing out the current configuration to a new file.
Finally, you can also edit configuration files directly. Double-click on a build configuration file to open it in the associated build configuration editor. This action presents a tree view of the source files in the project, with checkboxes to add or remove resources from the configuration, as shown in Figure 9.
Figure 9. Build configuration editor
Tutorial Pages:
» Updated tools make AOP easier for beginners and veterans alike
» Installing AJDT
» First steps
» The Outline view and editor markers
» The Spacewar example
» Build configurations
» Aspect Visualization perspective
» Debugging
» Generating documentation
» Further options
» Conclusion
» Resources
First published by IBM DeveloperWorks
