ProcessTableItems.java

/*******************************************************************************
 * Copyright (c) 2008 Pierre-Antoine Grégoire.
 * 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
 *
 * Contributors:
 *    Pierre-Antoine Grégoire - initial API and implementation
 *******************************************************************************/
package org.org.eclipse.core.utils.platform.extensions;

import org.eclipse.core.runtime.CoreException;
import org.eclipse.core.runtime.IConfigurationElement;
import org.eclipse.core.runtime.IExtensionPoint;
import org.eclipse.core.runtime.IExtensionRegistry;
import org.eclipse.core.runtime.Platform;
import org.eclipse.ui.WorkbenchException;
import org.org.eclipse.core.utils.platform.Messages;
import org.org.eclipse.core.utils.platform.PlatformUtilsPlugin;
import org.org.eclipse.core.utils.platform.properties.ITabItemDefinition;
import org.org.eclipse.core.utils.platform.properties.PropertyPageTabItems;


/**
 * This class processes the extensions defined in other plugins in order to add them to the common preferences.
 * @author pagregoire
 */
public final class ProcessTableItems {
//    private static Logger logger = Logger.getLogger(ProcessTableItems.class);

    private ProcessTableItems() {
    }

    /**
     * The fully-qualified name of the functions extension-point for this plug-in.
     */
    private static final String EXTENSION_POINT = "org.org.eclipse.core.utils.platform.PropertyPageTabItems"; //$NON-NLS-1$

    /**
     * Name of the XML attribute designating a function's name.
     */
    private static final String TAB_NAME_ATTRIBUTE = "name"; //$NON-NLS-1$

    /**
     * Name of the XML attribute designating the fully-qualified name of the implementation class of a function.
     */
    private static final String CLASS_ATTRIBUTE = "class"; //$NON-NLS-1$

    private static boolean processed = false;

    /**
     * Perform initial extension processing for the members of the <code>functions</code> extension-point. Make calls to the user interface module to add the functions of an extension to the UI functions grid. For each function, a virtual proxy callback object is created and handed to the user interface module. The proxy class is a nested top-level class and is therefore known at compile time. The actual (real) callback objects configured into extensions are instantiated and initialized in a lazy fashion by the proxy callback objects.
     * 
     * @param grid The UI functions grid exposing the functions configured into <code>functions</code> extensions.
     *  
     */
    public static void process() throws WorkbenchException, CoreException {
        if (!processed) {
            IExtensionRegistry registry = Platform.getExtensionRegistry();
//            IExtensionPoint[] extensionPoints = registry.getExtensionPoints();
            IExtensionPoint extensionPoint = registry.getExtensionPoint(EXTENSION_POINT);
            if (extensionPoint == null) {
                throw new WorkbenchException(Messages.ProcessTableItems_error_extensionpointresolution + EXTENSION_POINT);
            }
            IConfigurationElement[] members = extensionPoint.getConfigurationElements();

            // For each service:
            for (int m = 0; m < members.length; m++) {
                IConfigurationElement member = members[m];
                // Get the label of the extender plugin and the ID of the extension.
                String pluginLabel = (String) PlatformUtilsPlugin.getDefault().getBundle().getHeaders().get(org.osgi.framework.Constants.BUNDLE_NAME);
                if (pluginLabel == null) {
                    pluginLabel = "[unnamed plugin]"; //$NON-NLS-1$
                }
                // Get the name of the operation implemented by the service.
                // The operation name is a service attribute in the extension's XML specification.
                String tabName = member.getAttribute(TAB_NAME_ATTRIBUTE);
                if (tabName == null) {
                    tabName = "[unnamed function]"; //$NON-NLS-1$
                }
                Object callback = null;
                callback = member.createExecutableExtension(CLASS_ATTRIBUTE);
                if (callback == null) {
                    throw new WorkbenchException(Messages.ProcessTableItems_error_extensionloading + CLASS_ATTRIBUTE);
                }
                if (callback instanceof ITabItemDefinition) {
                    ITabItemDefinition tabItem = (ITabItemDefinition) callback;
                    PropertyPageTabItems.addTabItem(tabItem);
                }
            }
            processed = true;
        }
    }

}