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		<title>modulecore api overview</title>
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		<h1>jst j2ee</h1>
		<h2>Overview</h2>

		<BR />
		<P>
			The purpose of the following document is to highlight the API exposed as
			part of the Web Tools Platform Project for the creation and access of
			flexible project structures using the new ModuleCore API. 
		</P>

		<h2>Module Structural Model (MSM) Metamodel</h2>
		<BR />
		<p>
			The Module Structural Model (MSM) is an EMF model that allows the tooling
			to understand most project structures. Each project has a single (MSM)
			which is stored under the project root named
			<I>.wtpmodules</I>
			. The XML format is defined by the Module Core namespace (
			<a href="http://www.eclipse.org/webtools/moduleCore.xsd">
				http://www.eclipse.org/webtools/moduleCore
			</a>
			). The following diagram is a UML representation of the metamodel.
			<table
				cellspacing="10"
				cellpadding="10">
				<tr>
					<td>
						<p>
							<img src="./diagrams/module_structural_model.jpg" />
						</p>
					</td>
				</tr>
				<tr>
					<td>
						<p>
							<i>Figure 1: The Module Structural Model API</i>
						</p>
					</td>
				</tr>
			</table>
		</p>
		<p>
			Each logical module contained in the project is represented by a
			WorkbenchModule element. The WorkbenchModule defines information about
			the type of module, the resources consumed by the module from the
			project, and the dependent modules. The WorkbenchModule is very generic,
			and as modeled, does not necessarily correspond to only J2EE artifacts.
		</p>
		<p>
			The WorkbenchModule has a
			<i>deployedName</i>
			, which is the name that will be used when the deployable form of the
			module is constructed. For a web application, the
			<i>deployedName</i>
			might be "MyWebApplication.war".
		</p>
		<p>
			The WorkbenchModule may be uniquely referenced by a URI (stored on the
			WorkbenchModule as the
			<i>handle</i>
			). The fully qualified URI to any module must begin with the module
			protocol ("module:"), specify a subprotocol ("resource|classpath") and
			then a path to the referenced module. A WorkbenchModule with the
			deplyedName "MyWebApplication.war" defined in a project named
			"MyWebModulesProject" would be referenced by the following URI:
			"module:/resource/MyWebModulesProject/MyWebApplication.war".
		</p>
		<p>
			The WorkbenchModule has a ModuleType. The ModuleType defines a
			<i>moduleTypeId</i>
			, which indicates the specific kind of module. The Web Tools Platform
			uses the
			<i>moduleTypeId</i>
			to determine how to work with the content module of the WorkbenchModule
			and prepare the module for deployment. The ModuleType may also define the
			runtime-paths of special metadata resources which are important to the
			WorkbenchModule. "Metadata" refers to resources which explain the content
			details of the specific modules. An example of such a file would be the
			"WEB-INF/web.xml" deployment descriptor for Web Applications.
		</p>
		<p>
			The WorkbenchModule contains a list of WorkbenchModuleResources. Each
			WorkbenchModuleResource has "sourcePath" and a corresponding
			"deployedPath". The "sourcePath" can reference either a file or folder,
			but the referenced resource must be contained in the same project as the
			WorkbenchModule definition. The "deployedPath" specifies a location
			relative to the deployed structure of the WorbenchModule where the
			contents of the referenced resource will be placed when the module is
			prepared for deployment.
		</p>
		<p>
			The WorkbenchModule contains a list of DependentModules. Each
			DependentModule provides a handle that must resolve to a WorkbenchModule,
			a deployedPath that defines where the constructed module will be placed
			within the context of the deployed WorkbenchModule, and a DependencyType
			that can be either "consume" or "use" to indicate how the contents of
			that DependentModule should be absorbed by the WorkbenchModule.
			DependentModules may reference WorkbenchModules in other projects and on
			the classpath. The DependencyType will determine whether the contents of
			the DependentModule are absorbed as-is or archived into a *.{w|j|e}ar
			file.
		</p>
		<p>
			The ProjectModules object provides a root container for all
			WorkbenchModules defined in a given project.
		</p>
		<p>
			ModuleCore provides an instance facade to manage the underlying model for
			clients. Static methods
			<code>ModuleCore.getModuleCoreForRead()</code>
			and
			<code>ModuleCore.getModuleCoreForWrite()</code>
			may be used to acquire an ModuleCore adapter, and clients are responsible
			for invoking
			<code>dispose()</code>
			whenever they are finished using the model.
		</p>

		<h2>Constraints enforced by the MSM</h2>
		<p>
			The following constraints are enforced by the model or by components in
			the Web Tools Platform that use the model.
			<ol>
				<li>
					<p>
						The solution will not check dependencies for modules that are
						contained in the same project. To get the full benefits of
						inter-module dependency checking, modules must be separated
						into different projects. We do not have the necessary
						flexibility in constructing and scoping classpaths on a level
						more granular than the project level, which would be needed
						to support this functionality.
					</p>
				</li>
				<li>
					<p>
						The solution will not allow a single module to span more than
						one project. Within that project, we will have fairly broad
						flexibility to specify which resources map to which modules.
						Each module within a project must have its own source folder,
						but a module may contain more than one source folder. Each
						source folder may be contained by at most one module. Modules
						may reference dependent modules in other projects (so a Web
						Application may reference a Web Library outside of the
						project that contains the Web Application).
					</p>
				</li>
				<li>
					<p>
						The solution will not allow more than one server target per
						module (and really per-project) at a time. The ability to
						switch this server target (via some action or property
						setting) will continue to be possible. Users that need the
						capability to develop for multiple server targets will need
						to manually switch and test as necessary.
					</p>
				</li>
				<li>
					<p>
						Each module in a project will have its own output folder
						structure automatically constructed for it. The output
						structure will match the J2EE specification output structure
						required for the module type (for J2EE modules). A new
						builder will handle this responsibility and work
						cooperatively with the Java builder to construct a
						deployable, on-disk representation of the module structure.
						The necessity for this on-disk structure to match a
						J2EE-compliant layout is motivated by the requirement to have
						in-workbench testing, so that users will not have to deal
						with a deployer actually constructing a deployable module and
						shipping it off to a server to test their code. This approach
						is consistent with existing Ant-based approaches and
						Application Servers which can run in a "debug" mode on disk.
						Our value-add will be greater automation and integration with
						the workbench -- particularly for incremental based support.
						The specialized module builder would not be necessary if the
						source was already in the appropriate J2EE specification
						compliant structure. The default creation will still
						encourage a single module per project, which conforms to the
						correct J2EE structure.
					</p>
				</li>
				<li>
					<p>
						Modules will be described using a simple XML format, and each
						project will contain one
						<I>.wtpmodules</I>
						file that will describe all of the modules for that project.
						The level of tooling to help users create these files is yet
						to be determined for WTP M4. This would be a great area for
						other interested developers to suggest and provide tooling
						(e.g. a Wizard or Editor) to create these files from existing
						structures. A schema is provided to make it easier for
						consumers that want to build their own
						<I>.wtpmodules</I>
						by hand to take advantage of the content assist in the XML
						editor.
					</p>
				</li>
			</ol>
		</p>
		<h2>ModuleCore API: Working with the metamodel</h2>
		<BR />
		<p>
			Clients that need to work with the Module Structural Model should use the
			ModuleCore API to access the model for each project. ModuleCore uses a
			mixed pattern that contains elements of Adapter and Facade. Each
			ModuleCore is tied to a specific project, and manages the complexity of
			the lifecycle of the underlying model.
			<table
				cellspacing="10"
				cellpadding="10">
				<tr>
					<td>
						<p>
							<img src="./diagrams/modulecore.jpg" />
						</p>
					</td>
				</tr>
				<tr>
					<td>
						<p>
							<i>Figure 2: The ModuleCore API</i>
						</p>
					</td>
				</tr>
			</table>
		</p>
		<p>
			Clients should use one of
			<code>ModuleCore.getModuleCoreForRead()</code>
			or
			<code>ModuleCore.getModuleCoreForWrite()</code>
			to acquire an instance of ModuleCore.
			<table
				cellspacing="10"
				cellpadding="10">
				<tr>
					<td>
						<pre>
IProject currentProject = ... 
ModuleCore moduleCoreInstance = ModuleCore.getModuleCoreForRead(currentProject);
WorkbenchModule[] modules = moduleCoreInstance.getWorkbenchModules(); 
... work with modules ... 
moduleCoreInstance.dispose();
						</pre>
					</td>
				</tr>
				<tr>
					<td>
						<p>
							<i>
								Figure 3: Acquiring an instance of ModuleCore for
								read-only access
							</i>
						</p>
					</td>
				</tr>
			</table>
		</p>
		<p>
			For clients that would like to build up their own models for a given
			project, or modify the existing metamodel, the ModuleCore instance should
			be acquired for write-access.
			<table
				cellspacing="10"
				cellpadding="10">
				<tr>
					<td>
						<pre>

...
import org.eclipse.emf.common.util.URI; 
...

    public static void createWebAppModule(IProject aTargetProject, 
                          IFolder aJavaSourceFolder, 
                          IFolder aWebContentFolder, 
                          IResource aWebAppDeploymentDescriptor, 
                          IProgressMonitor aProgressMonitor) 
    {
        ModuleCore moduleCoreInstance = null;
		try {
			moduleCoreInstance = ModuleCore.getModuleCoreForWrite(aTargetProject);

			/* Create a new module that will be contained by the current ModuleCore */
			WorkbenchModule newModule = moduleCoreInstance.createWorkbenchModule("MyWebModule.war");

			/* A Java source folder that contains the classes for the current module */
			WorkbenchModuleResource javaSource = 
				moduleCoreInstance.createWorkbenchModuleResource(aJavaSourceFolder);
			javaSource.setDeployedPath(URI.createURI("/WEB-INF/classes"));
			newModule.getResources().add(javaSource);

			/* A resource folder that contains the *.jsp, *.html, .img, ... files */
			WorkbenchModuleResource webContent = 
				moduleCoreInstance.createWorkbenchModuleResource(aWebContentFolder);
			webContent.setDeployedPath(URI.createURI("/"));
			newModule.getResources().add(webContent);

			/*
			 * A resource that points to a valid web.xml file that follows the J2EE Web Deployment
			 * Descriptor Specification
			 */
			WorkbenchModuleResource deploymentDescriptor = 
				moduleCoreInstance.createWorkbenchModuleResource(aWebAppDeploymentDescriptor);
			deploymentDescriptor.setDeployedPath(URI.createURI("/WEB-INF/web.xml"));
			newModule.getResources().add(deploymentDescriptor);

			moduleCoreInstance.saveIfNecessary(aProgressMonitor);
		} finally {
			if (moduleCoreInstance != null) {
				moduleCoreInstance.dispose();
			}
		}
	}
						</pre>
					</td>
				</tr>
				<tr>
					<td>
						<p>
							<i>Figure 4: Creating a WorkbenchModule</i>
						</p>
					</td>
				</tr>
			</table>
		</p>
		<p>
			For clients that would like to take an existing project an add Flexible
			Project Support, use the ModuleCoreNature.addModuleCoreIfNecessary() API
			to prepare the project to support flexible module structures. the
			existing metamodel, then acquire the ModuleCore instance for modification.
			<table
				cellspacing="10"
				cellpadding="10">
				<tr>
					<td>
						<pre>
... 
import org.eclipse.emf.common.util.URI; 
...
	public static void makeFlexible(IProject aTargetProject) {
		ModuleCore moduleCoreInstance = null;
		try {
			ModuleCoreNature.addModuleCoreNatureIfNecessary(aTargetProject);
			moduleCoreInstance = ModuleCore.getModuleCoreForWrite(aTargetProject);
			... work with moduleCoreInstance and underlying model ...
			moduleCoreInstance.saveIfNecessary(aProgressMonitor);
		} finally {
			if (moduleCoreInstance != null) {
				moduleCoreInstance.dispose();
			}
		}
	}
						</pre>
					</td>
				</tr>
				<tr>
					<td>
						<p>
							<i>Figure 5: Add Flexible Project support to a new or existing project</i>
						</p>
					</td>
				</tr>
			</table>
		</p>
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