Extending Eclipse: creating a Java project without displaying a wizard

November 18th, 2008

The usual way of creating a Java project is by showing a wizard that guides the user through the different configuration options. In case you want to customize the existing wizard (add a new page, for example), you specify the org.eclipse.ui.newWizards extension point in your plugin.xml and specify a new wizard section with project attribute set to true. But what if you want to create a new Java project in a purely programmatical way without showing any wizard dialog?

The published API to configure the Java project is the org.eclipse.jdt.ui.wizards.JavaCapabilityConfigurationPage. It has two public utility methods, createProject and configureJavaProject that do most of the heavy lifting. The first problem is that the second method is not static (which means that you need an instance of this page to call it), and the second problem is that the implementation of these methods is calling into internal classes. Fortunately, all the APIs that are required to create a new custom Java project are published. Let’s take a look at the sequence of steps.

First, call ResourcesPlugin.getWorkspace().getRoot().getProject(projectName) to get the IProject handle. Calling exists() will let you know whether the project named projectName already exists. All the following steps assume that this project does not yet exist.

Next, call project.create and project.open. This will create and open the new project.

Now it’s time to create the source folders for the project. Suppose you want to create a source folder named custom. Start by creating a new IPath instance with IPath customPath = new Path(“custom“). Next, call IFolder customFolder = project.getFolder(customPath) and finally customFolder.create(true, true, null). If you have more than one source folder, repeat the steps above for each one of them. A source folder can be a link to a directory on your hard disk. To mark the source folder as link, call IFolder.createLink API, passing the path to the hard disk location. The second parameter can be IResource.ALLOW_MISSING_LOCAL to allow the creation of the link source folder even if the linked target folder does not (yet) exist.

Next step is configuring the classpath entries for the new project. The classpath entries include:

  • your source folders
  • your custom jars
  • the JRE container

To create an IClasspathEntry instance that corresponds to your source folder, call JavaCore.newSourceEntry(project.getFullPath().append(customPath)) where customPath is the IPath instance created above.

The simplest way to create the classpath entries for the JRE container is to use the PreferenceConstants.getDefaultJRELibrary() method. This will return the classpath entries for the default JRE of the workspace. If you want to use another JRE, you would need to iterate through the VM install types returned by the JavaRuntime.getVMInstallTypes(), and iterate through the VM installs for each one of them. The IVMInstall does not expose an API to check its Java compliance. Cast it to AbstractVMInstall and check its getJavaVersion() to the specific compliance spec string (such as JavaCore.VERSION_1_6 for Java 6.0, for example). Once you find a matching JRE, you can get its classpath entries with the following:

  • Get the JRE container path with IPath containerPath=new Path(JavaRuntime.JRE_CONTAINER)
  • Assuming that you have found a matching AbstractVMInstall, create its path by IPath vmPath = containerPath.append(vmInstall.getVMInstallType().getId()).append(vmInstall.getName())
  • Now, the classpath entry of that JRE is simply JavaCore.newContainerEntry(vmPath)

To create a classpath entry for a custom jar (with optional javadoc and source attachments), use JavaCore.newLibraryEntry API. The first parameter is the path to the jar file that can be constructed with the various FileLocator APIs. The sources can be specified via the second and the third parameters. The javadoc attachment is passed in the classpath attribute array (fifth parameter). To construct an IClasspathAttribute entry, use JavaCore.newClasspathAttribute API with IClasspathAttribute.JAVADOC_LOCATION_ATTRIBUTE_NAME name and “file:filePath” value where the filePath is the URL of your javadoc file.

Next step is to create a IJavaProject by using IJavaProject javaProject=JavaCore.create(project).

Next step is to add the Java nature to the new project. This is done by getting the IProjectDescription of the project with the IProject.getDescription, creating a new String[] array to hold an additional entry, copying all the existing nature IDs (from IProjectDescription.getNatureIds() API), adding the JavaCore.NATURE_ID entry and setting back the description.

Next step is to create the default output folder for the project. The name of the default output folder can be taken from the PreferenceConstants.getPreferenceStore().getString(PreferenceConstants.SRCBIN_NAME) and the folder itself is created with the same IProject.getFolder and IFolder.create APIs as for the source folders. The only difference is in that the output folder needs to be marked as derived. In order to do this, pass IResource.FORCE | IResource.DERIVED as the first parameter to the IFolder.create method and call IFolder.setDerived(true) afterward.

At this point, the project is ready to be refreshed (before the actual classpath is set). Call project.refreshLocal with IResource.DEPTH_INFINITE).

Next step is to set the classpath on the java project. Call javaProject.setRawClasspath passing the array of all the classpath entries created before.

The next optional step involves setting custom natures and moving the Java builder in the builder sequence. If your project is going to have a custom nature with custom builders, you first need to add the custom nature(s) to the project description. This is done in exactly the same way as with the java nature above. After setting the nature, you might want to move the default Java builder down in the sequence. This is relevant if the Java builder (the one that compiles the source Java classes) needs to be invoked after your custom builder(s) – the ones that generate additional Java classes, perhaps. To do so, get the build spec sequence from IProjectDescription.getBuildSpec array and shuffle the commands as necessary.

The final step is to set the Java compliance settings on the project. This is done to enforce the different Java rules. Get the current settings from IJavaProject.getJavaOptions. Next, set the following entries in the map:

  • JavaCore.COMPILER_COMPLIANCE to the matching JavaCore constant, such as JavaCore.VERSION_1_6.
  • JavaCore.COMPILER_SOURCE to the matching JavaCore constant, such as JavaCore.VERSION_1_6.
  • JavaCore.COMPILER_CODEGEN_TARGET_PLATFORM to the matching JavaCore constant, such as JavaCore.VERSION_1_6.
  • JavaCore.COMPILER_PB_ASSERT_IDENTIFIER to JavaCore.ERROR to prevent using assert as a valid identifier.
  • JavaCore.COMPILER_PB_ENUM_IDENTIFIER to JavaCore.ERROR to prevent using enum as a valid identifier.

After setting these entries, store the options back with IJavaProject.setOptions

Congratulations – now you have a new Java project with custom source folders (some of them linked), custom jars, an output folder and custom builders set. And all of this without the user having to click through the wizard screens.