org.summer.dsl.builder.impl.RegistryBuilderParticipant.java Source code

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Here is the source code for org.summer.dsl.builder.impl.RegistryBuilderParticipant.java

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/*******************************************************************************
 * Copyright (c) 2010 itemis AG (http://www.itemis.eu) 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
 *******************************************************************************/
package org.summer.dsl.builder.impl;

import java.util.Map;

import org.apache.log4j.Logger;
import org.eclipse.core.runtime.CoreException;
import org.eclipse.core.runtime.IConfigurationElement;
import org.eclipse.core.runtime.IExtension;
import org.eclipse.core.runtime.IExtensionRegistry;
import org.eclipse.core.runtime.IProgressMonitor;
import org.eclipse.core.runtime.OperationCanceledException;
import org.eclipse.core.runtime.SubMonitor;
import org.eclipse.emf.ecore.plugin.RegistryReader;
import org.summer.dsl.builder.IXtextBuilderParticipant;
import org.summer.dsl.builder.internal.Activator;

import com.google.common.collect.ImmutableList;
import com.google.common.collect.Maps;
import com.google.inject.Inject;
import com.google.inject.Singleton;

/**
 * @author Sebastian Zarnekow - Initial contribution and API
 * @author Jan Koehnlein
 */
@Singleton
public class RegistryBuilderParticipant implements IXtextBuilderParticipant {

    private static final String PARTICIPANT = "participant"; //$NON-NLS-1$

    private static final String EXTENSION_POINT_ID = PARTICIPANT;

    private static final String ATT_CLASS = "class"; //$NON-NLS-1$

    private static final Logger readerLog = Logger.getLogger(BuilderParticipantReader.class);

    @Inject
    private IExtensionRegistry extensionRegistry;

    private volatile ImmutableList<IXtextBuilderParticipant> participants;

    private Map<String, IXtextBuilderParticipant> classToParticipant;

    public void build(IBuildContext buildContext, IProgressMonitor monitor) throws CoreException {
        ImmutableList<IXtextBuilderParticipant> participants = getParticipants();
        if (participants.isEmpty())
            return;
        SubMonitor progress = SubMonitor.convert(monitor, participants.size());
        progress.subTask(Messages.RegistryBuilderParticipant_InvokingBuildParticipants);
        for (IXtextBuilderParticipant participant : participants) {
            if (progress.isCanceled())
                throw new OperationCanceledException();
            participant.build(buildContext, progress.newChild(1));
        }
    }

    public ImmutableList<IXtextBuilderParticipant> getParticipants() {
        ImmutableList<IXtextBuilderParticipant> result = participants;
        if (participants == null) {
            result = initParticipants();
        }
        return result;
    }

    protected synchronized ImmutableList<IXtextBuilderParticipant> initParticipants() {
        ImmutableList<IXtextBuilderParticipant> result = participants;
        if (result == null) {
            if (classToParticipant == null) {
                classToParticipant = Maps.newHashMap();
                String pluginID = Activator.getDefault().getBundle().getSymbolicName();
                String extensionPointID = EXTENSION_POINT_ID;
                BuilderParticipantReader reader = new BuilderParticipantReader(extensionRegistry, pluginID,
                        extensionPointID);
                reader.readRegistry();
            }
            result = ImmutableList.copyOf(classToParticipant.values());
            participants = result;
        }
        return result;
    }

    public class BuilderParticipantReader extends RegistryReader {

        public BuilderParticipantReader(IExtensionRegistry pluginRegistry, String pluginID,
                String extensionPointID) {
            super(pluginRegistry, pluginID, extensionPointID);
        }

        @Override
        protected boolean readElement(IConfigurationElement element, boolean add) {
            if (element.getName().equals(PARTICIPANT)) {
                String className = element.getAttribute(ATT_CLASS);
                if (className == null) {
                    logMissingAttribute(element, ATT_CLASS);
                } else if (add) {
                    try {
                        Object participant = element.createExecutableExtension(ATT_CLASS);
                        if (participant instanceof IXtextBuilderParticipant) {
                            if (classToParticipant.containsKey(className)) {
                                readerLog.warn("The builder participant '" + className + "' was registered twice."); //$NON-NLS-1$ //$NON-NLS-2$
                            }
                            classToParticipant.put(className, (IXtextBuilderParticipant) participant);
                            participants = null;
                        } else {
                            logError(element,
                                    className + " did not yield an instance of IXtextBuilderParticipant but " + //$NON-NLS-1$
                                            participant.getClass().getName());
                        }
                        return true;
                    } catch (CoreException e) {
                        logError(element, e.getMessage());
                    }
                } else {
                    classToParticipant.remove(className);
                    participants = null;
                    return true;
                }
            }
            return false;
        }

        @Override
        protected void logError(IConfigurationElement element, String text) {
            IExtension extension = element.getDeclaringExtension();
            readerLog.error("Plugin " + extension.getContributor().getName() + ", extension " //$NON-NLS-1$//$NON-NLS-2$
                    + extension.getExtensionPointUniqueIdentifier());
            readerLog.error(text);
        }

    }

}