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Overview
 
 

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.

Module Structural Model (MSM) Metamodel
 
 

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 .wtpmodules . The XML format is defined by the Module Core namespace ( http://www.eclipse.org/webtools/moduleCore ). The following diagram is a UML representation of the metamodel.

Figure 1: The Module Structural Model API

 

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.

 

The WorkbenchModule has a deployedName , which is the name that will be used when the deployable form of the module is constructed. For a web application, the deployedName might be "MyWebApplication.war".

 

The WorkbenchModule may be uniquely referenced by a URI (stored on the WorkbenchModule as the handle ). 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".

 

The WorkbenchModule has a ModuleType. The ModuleType defines a moduleTypeId , which indicates the specific kind of module. The Web Tools Platform uses the moduleTypeId 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.

 

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.

 

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.

 

The ProjectModules object provides a root container for all WorkbenchModules defined in a given project.

 

ModuleCore provides an instance facade to manage the underlying model for clients. Static methods ModuleCore.getModuleCoreForRead() and ModuleCore.getModuleCoreForWrite() may be used to acquire an ModuleCore adapter, and clients are responsible for invoking dispose() whenever they are finished using the model.

Constraints enforced by the MSM
 

The following constraints are enforced by the model or by components in the Web Tools Platform that use the model.

  1. 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.

  2. 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).

  3. 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.

  4. 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.

  5. Modules will be described using a simple XML format, and each project will contain one .wtpmodules 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 .wtpmodules by hand to take advantage of the content assist in the XML editor.

ModuleCore API: Working with the metamodel
 
 

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.

Figure 2: The ModuleCore API

 

Clients should use one of ModuleCore.getModuleCoreForRead() or ModuleCore.getModuleCoreForWrite() to acquire an instance of ModuleCore. 
IProject currentProject = ... 
ModuleCore moduleCoreInstance = ModuleCore.getModuleCoreForRead(currentProject);
WorkbenchModule[] modules = moduleCoreInstance.getWorkbenchModules(); 
... work with modules ... 
moduleCoreInstance.dispose();

Figure 3: Acquiring an instance of ModuleCore for read-only access

 

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. 

...
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();
			}
		}
	}

Figure 4: Creating a WorkbenchModule

 

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. 
... 
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();
			}
		}
	}

Figure 5: Add Flexible Project support to a new or existing project