/*******************************************************************************
* Copyright (c) 2000, 2007 IBM Corporation and others.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* IBM Corporation - added support for requesting updates of a particular
* container for generic container operations.
* - canUpdateBuildpathContainer(IPath, IScriptProject)
* - requestBuildpathContainerUpdate(IPath, IScriptProject, IBuildpathContainer)
* IBM Corporation - allow initializers to provide a readable description
* of a container reference, ahead of actual resolution.
* - getDescription(IPath, IScriptProject)
*******************************************************************************/
package org.eclipse.dltk.core;
import org.eclipse.core.runtime.CoreException;
import org.eclipse.core.runtime.IPath;
/**
* Abstract base implementation of all buildpath container initializer.
* Buildpath variable containers are used in conjunction with the
* "org.eclipse.dltk.core.buildpathContainerInitializer" extension point.
* <p>
* Clients should subclass this class to implement a specific buildpath
* container initializer. The subclass must have a public 0-argument
* constructor and a concrete implementation of <code>initialize</code>.
* <p>
* Multiple buildpath containers can be registered, each of them declares
* the container ID they can handle, so as to narrow the set of containers they
* can resolve, in other words, a container initializer is guaranteed to only be
* activated to resolve containers which match the ID they registered onto.
* <p>
* In case multiple container initializers collide on the same container ID, the first
* registered one will be invoked.
*
* @see IBuildpathEntry
* @see IBuildpathContainer
*
*/
public abstract class BuildpathContainerInitializer {
/**
* Creates a new buildpath container initializer.
*/
public BuildpathContainerInitializer() {
// a buildpath container initializer must have a public 0-argument constructor
}
/**
* Binds a buildpath container to a <code>IBuildpathContainer</code> for a given project,
* or silently fails if unable to do so.
* <p>
* A container is identified by a container path, which must be formed of two segments.
* The first segment is used as a unique identifier (which this initializer did register onto), and
* the second segment can be used as an additional hint when performing the resolution.
* <p>
* The initializer is invoked if a container path needs to be resolved for a given project, and no
* value for it was recorded so far. The implementation of the initializer would typically set the
* corresponding container using <code>DLTKCore#setBuildpathContainer</code>.
* <p>
* A container initialization can be indirectly performed while attempting to resolve a project
* buildpath using <code>IScriptProject#getResolvedBuildpath(</code>; or directly when using
* <code>DLTKCore#getBuildpathContainer</code>. During the initialization process, any attempt
* to further obtain the same container will simply return <code>null</code> so as to avoid an
* infinite regression of initializations.
* <p>
* A container initialization may also occur indirectly when setting a project buildpath, as the operation
* needs to resolve the buildpath for validation purpose. While the operation is in progress, a referenced
* container initializer may be invoked. If the initializer further tries to access the referring project buildpath,
* it will not see the new assigned buildpath until the operation has completed. Note that once the Script language
* change notification occurs (at the end of the operation), the model has been updated, and the project
* buildpath can be queried normally.
* <p>
* This method is called by the Script language model to give the party that defined
* this particular kind of buildpath container the chance to install
* buildpath container objects that will be used to convert buildpath
* container entries into simpler buildpath entries. The method is typically
* called exactly once for a given Script language project and buildpath container
* entry. This method must not be called by other clients.
* <p>
* There are a wide variety of conditions under which this method may be
* invoked. To ensure that the implementation does not interfere with
* correct functioning of the Script language model, the implementation should use
* only the following Script language model APIs:
* <ul>
* <li>{@link DLTKCore#setBuildpathContainer(IPath, IScriptProject[], IBuildpathContainer[], org.eclipse.core.runtime.IProgressMonitor)}</li>
* <li>{@link DLTKCore#getBuildpathContainer(IPath, IScriptProject)}</li>
* <li>{@link DLTKCore#create(org.eclipse.core.resources.IWorkspaceRoot)}</li>
* <li>{@link DLTKCore#create(org.eclipse.core.resources.IProject)}</li>
* <li>{@link IScript languageModel#getScript languageProjects()}</li>
* <li>Script language element operations marked as "handle-only"</li>
* </ul>
* The effects of using other Script language model APIs are unspecified.
* </p>
*
* @param containerPath a two-segment path (ID/hint) identifying the container that needs
* to be resolved
* @param project the Script language project in which context the container is to be resolved.
* This allows generic containers to be bound with project specific values.
* @throws CoreException if an exception occurs during the initialization
*
* @see DLTKCore#getBuildpathContainer(IPath, IScriptProject)
* @see DLTKCore#setBuildpathContainer(IPath, IScriptProject[], IBuildpathContainer[], org.eclipse.core.runtime.IProgressMonitor)
* @see IBuildpathContainer
*/
public abstract void initialize(IPath containerPath, IScriptProject project) throws CoreException;
/**
* Returns <code>true</code> if this container initializer can be requested to perform updates
* on its own container values. If so, then an update request will be performed using
* <code>BuildpathContainerInitializer#requestBuildpathContainerUpdate</code>/
* <p>
* @param containerPath the path of the container which requires to be updated
* @param project the project for which the container is to be updated
* @return returns <code>true</code> if the container can be updated
*
*/
public boolean canUpdateBuildpathContainer(IPath containerPath, IScriptProject project) {
// By default, buildpath container initializers do not accept updating containers
return false;
}
/**
* Request a registered container definition to be updated according to a container suggestion. The container suggestion
* only acts as a place-holder to pass along the information to update the matching container definition(s) held by the
* container initializer. In particular, it is not expected to store the container suggestion as is, but rather adjust
* the actual container definition based on suggested changes.
* <p>
* IMPORTANT: In reaction to receiving an update request, a container initializer will update the corresponding
* container definition (after reconciling changes) at its earliest convenience, using
* <code>DLTKCore#setBuildpathContainer(IPath, IScriptProject[], IBuildpathContainer[], IProgressMonitor)</code>.
* Until it does so, the update will not be reflected in the Script language Model.
* <p>
* In order to anticipate whether the container initializer allows to update its containers, the predicate
* <code>DLTKCore#canUpdateBuildpathContainer</code> should be used.
* <p>
* @param containerPath the path of the container which requires to be updated
* @param project the project for which the container is to be updated
* @param containerSuggestion a suggestion to update the corresponding container definition
* @throws CoreException when <code>DLTKCore#setBuildpathContainer</code> would throw any.
* @see DLTKCore#setBuildpathContainer(IPath, IScriptProject[], IBuildpathContainer[], org.eclipse.core.runtime.IProgressMonitor)
* @see BuildpathContainerInitializer#canUpdateBuildpathContainer(IPath, IScriptProject)
*
*/
public void requestBuildpathContainerUpdate(IPath containerPath, IScriptProject project, IBuildpathContainer containerSuggestion) throws CoreException {
// By default, buildpath container initializers do not accept updating containers
}
/**
* Returns a readable description for a container path. A readable description for a container path can be
* used for improving the display of references to container, without actually needing to resolve them.
* A good implementation should answer a description consistent with the description of the associated
* target container (see <code>IBuildpathContainer.getDescription()</code>).
*
* @param containerPath the path of the container which requires a readable description
* @param project the project from which the container is referenced
* @return a string description of the container
*
*/
public String getDescription(IPath containerPath, IScriptProject project) {
// By default, a container path is the only available description
return containerPath.makeRelative().toString();
}
/**
* Returns an object which identifies a container for comparison purpose. This allows
* to eliminate redundant containers when accumulating buildpath entries (e.g.
* runtime buildpath computation). When requesting a container comparison ID, one
* should ensure using its corresponding container initializer. Indeed, a random container
* initializer cannot be held responsible for determining comparison IDs for arbitrary
* containers.
* <p>
* @param containerPath the path of the container which is being checked
* @param project the project for which the container is to being checked
* @return returns an Object identifying the container for comparison
*
*/
public Object getComparisonID(IPath containerPath, IScriptProject project) {
// By default, containers are identical if they have the same containerPath first segment,
// but this may be refined by other container initializer implementations.
if (containerPath == null) {
return null;
} else {
return containerPath.segment(0);
}
}
}