Eclipse Wrt Plugin Dev

Implementing Incremental Builder Project for an Eclipse Web Runtime Plugin Tasneem Sayeed Mobile Technologist September 16, 2009

Copyright © 2009 Symbian Foundation.

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Eclipse Web Runtime (WRT) Plugin Development 2 Key Mechanisms that are associated with projects in an Eclipse workspace:  Incremental project builders 

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Create some built state based on the project contents, and then keep that built state synchronized as the project contents change.

Project Natures 

Define and manage the association between a given project and a particular plug-in or feature.

Copyright © 2009 Symbian Foundation.

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Eclipse Incremental Project Builder Terminology 

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Builder - Builders take raw materials and produce some output based on those materials. In Eclipse, both the raw materials and the output of builders are resources in the Eclipse workspace. Incremental - It would be inefficient if builders rebuilt their entire output from scratch every time they were invoked. Instead, builders in Eclipse are incremental. This means that after the first build, subsequent builds should only rebuild based on what has changed since the last build. Project - A builder operates on the resources in a single project in the Eclipse workspace. If there are many projects in the workspace, builders need to be installed on each one separately.

Copyright © 2009 Symbian Foundation.

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How does the JavaScript builder know which files need to be recompiled …? 

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The Eclipse builder maintains a built state that includes a list of all types (classes or interfaces) that are referenced by each type in the workspace. This information is returned by the compiler each time a source file is compiled. This state is computed from scratch on a full build, and updated incrementally on each subsequent build. Whenever files are modified, the builder receives a resource delta that describes which files were added, removed, or changed. For deleted JavaScript source files, the corresponding class files are deleted. Added and changed source files are added to a queue of files that need to be compiled.

Copyright © 2009 Symbian Foundation.

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How does the JavaScript builder know which files need to be recompiled …? 

The builder then processes this queue as follows:  

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Remove a file from the queue, and compile it. Compare the resulting type to the old class file, and see if the type has structural changes. Structural changes are changes that can affect the compilation of a referencing type: added or removed methods, fields or types, or changed method signatures. If the type has structural changes, find all types in the project that reference the changed type, and add them to the queue. If the type has changed at all, write it to disk in the builder's output folder. Update the built state with the new reference information for the compiled type. Repeat until the queue is empty.

As a final step, the builder generates problem markers for each compiled type that had compilation problems.

Copyright © 2009 Symbian Foundation.

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Project Natures 

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Create an association between a project and a given tool, plug-in, or feature set. By adding a nature to a project, you indicate that your plug-in is configured to use that project. Natures also provide a way of handling the lifecycle of a tool's interaction with a project. When a nature is added to a project, the project nature's configure method is called. This gives the tool an opportunity to initialize its state for that project, and install any incremental project builders that are needed for that project. When a nature is removed from a project, the nature's deconfigure method is called. This gives the tool an opportunity to remove or clean up any meta-data it has created for that project, and to remove any listeners and builders associated with that tool.

Copyright © 2009 Symbian Foundation.

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Implementing Incremental Project Builder To implement an incremental project builder, you first have to create an extension for org.eclipse.core.resources.builders: <extension id="Builder" name="eScript Builder" point="org.eclipse.core.resources.builders"> <parameter name="optimize" value="true"/> <parameter name="comment" value="escriptBuilder"/>

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Copyright © 2009 Symbian Foundation.

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Implementing an Incremental Project Builder 

Create a Builder class that must extend the abstract IncrementalProjectBuilder superclass

public class Builder extends IncrementalProjectBuilder { protected IProject[] build(int kind, Map args, IProgressMonitor monitor) { if (kind == IncrementalProjectBuilder.FULL_BUILD) { fullBuild(monitor); } else { IResourceDelta delta = getDelta(getProject()); if (delta == null) { fullBuild(monitor); } else { incrementalBuild(delta, monitor); } } return null; } Copyright © 2009 Symbian Foundation.

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Implementing an Incremental Project Builder private void incrementalBuild(IResourceDelta delta, IProgressMonitor monitor) { System.out.println("incremental build on "+delta); try { delta.accept(new IResourceDeltaVisitor() { public boolean visit(IResourceDelta delta) { System.out.println("changed: "+ delta.getResource().getRawLocation()); return true; // visit children too } }); } catch (CoreException e) { e.printStackTrace(); } } private void fullBuild(IProgressMonitor monitor) { System.out.println("full build"); } } Copyright © 2009 Symbian Foundation.

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