Java tutorial
/** * Copyright (C) 2010 STMicroelectronics * * This file is part of "Mind Compiler" is free software: you can redistribute * it and/or modify it under the terms of the GNU Lesser General Public License * as published by the Free Software Foundation, either version 3 of the * License, or (at your option) any later version. * * This program is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS * FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more * details. * * You should have received a copy of the GNU Lesser General Public License * along with this program. If not, see <http://www.gnu.org/licenses/>. * * Contact: mind@ow2.org * * Authors: Matthieu Leclercq * Contributors: Ali Erdem Ozcan */ package org.ow2.mind.plugin; import java.io.FileNotFoundException; import java.io.IOException; import java.net.URL; import java.util.Enumeration; import java.util.HashMap; import java.util.Map; import java.util.logging.Level; import java.util.logging.Logger; import javax.xml.parsers.DocumentBuilder; import javax.xml.parsers.DocumentBuilderFactory; import javax.xml.parsers.ParserConfigurationException; import org.objectweb.fractal.adl.CompilerError; import org.objectweb.fractal.adl.error.GenericErrors; import org.objectweb.fractal.adl.util.FractalADLLogManager; import org.w3c.dom.Document; import org.w3c.dom.Element; import org.w3c.dom.Node; import org.w3c.dom.NodeList; import org.xml.sax.SAXException; import com.google.common.collect.Iterables; import com.google.inject.Inject; import com.google.inject.Injector; import com.google.inject.Singleton; import com.google.inject.name.Named; /** * Basic implementation of the {@link PluginManager} interface. */ @Singleton public class BasicPluginManager implements PluginManager { public final static String PLUGIN_CLASS_LOADER = "plugin-class-loader"; private static final String EXTENSION_POINT_ELEMENT_NAME = "extension-point"; private static final String EXTENSION_ELEMENT_NAME = "extension"; private static final String PLUGIN_NAME_ATTR_NAME = "name"; private static final String PLUGIN_ID_ATTR_NAME = "id"; public static final String PLUGIN_XML = "mind-plugin.xml"; protected PluginRegistry pluginRegistry; protected DocumentBuilder builder = null; @Inject @Named(PLUGIN_CLASS_LOADER) protected ClassLoader classLoader; @Inject protected Injector injector; protected static Logger pluginLogger = FractalADLLogManager.getLogger("plugin"); // --------------------------------------------------------------------------- // Constructor // --------------------------------------------------------------------------- public BasicPluginManager() { final DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance(); try { builder = builderFactory.newDocumentBuilder(); } catch (final ParserConfigurationException e) { throw new CompilerError(GenericErrors.INTERNAL_ERROR, e, "Can't initialize document builder"); } } // --------------------------------------------------------------------------- // Implementation of the PluginManager interface // --------------------------------------------------------------------------- public ExtensionPoint getExtensionPoint(final String extensionPoint) { return getRegistry().extensionPoints.get(extensionPoint); } public Iterable<Extension> getExtensions(final String extensionPoint) { final ExtensionPoint point = getExtensionPoint(extensionPoint); if (point == null) return null; return point.getExtensions(); } public Iterable<ConfigurationElement> getConfigurationElements(final String extensionPoint) { final ExtensionPoint point = getExtensionPoint(extensionPoint); if (point == null) return null; return point.getConfigurationElements(); } public Iterable<ConfigurationElement> getConfigurationElements(final String extensionPoint, final String name) { final ExtensionPoint point = getExtensionPoint(extensionPoint); if (point == null) return null; return point.getConfigurationElements(name); } public Iterable<String> getExtensionPointNames() { return Iterables.unmodifiableIterable(getRegistry().extensionPoints.keySet()); } public <T> T getInstance(final Class<T> clazz) { return injector.getInstance(clazz); } // --------------------------------------------------------------------------- // Utility classes and methods // --------------------------------------------------------------------------- protected PluginRegistry initRegistry() { final PluginRegistry registry = new PluginRegistry(); final ClassLoader classLoader = (this.classLoader != null) ? this.classLoader : this.getClass().getClassLoader(); Enumeration<URL> plugins = null; try { plugins = classLoader.getResources(PLUGIN_XML); } catch (final IOException e) { throw new CompilerError(GenericErrors.INTERNAL_ERROR, e, "Can't find plugin descriptors"); } while (plugins.hasMoreElements()) { final URL url = plugins.nextElement(); initPlugin(classLoader, url, registry); } // bind extensions to extension points : for (final Plugin plugin : registry.plugins.values()) { if (pluginLogger.isLoggable(Level.FINE)) { pluginLogger.fine("Initializing the plugin " + plugin.getId()); } for (final Extension extension : plugin.getExtensions()) { final ExtensionPointImpl point = registry.extensionPoints.get(extension.getExtensionPointID()); if (point == null) { throw new CompilerError(GenericErrors.INTERNAL_ERROR, "Unknown Extenstion point ID \"" + extension.getExtensionPointID() + "\" referenced by plugin \"" + plugin.getId() + "\"."); } point.bindExtension(extension); } } return registry; } protected void initPlugin(final ClassLoader classLoader, final URL pluginDesc, final PluginRegistry registry) { final Document document; try { document = builder.parse(pluginDesc.openStream()); } catch (final FileNotFoundException e) { throw new CompilerError(GenericErrors.INTERNAL_ERROR, e, "Unable to find the plugin descriptor '" + pluginDesc + "'."); } catch (final IOException e) { throw new CompilerError(GenericErrors.INTERNAL_ERROR, e, "Unable to access the plugin descriptor '" + pluginDesc + "'."); } catch (final SAXException e) { throw new CompilerError(GenericErrors.INTERNAL_ERROR, e, "Unable to parse the XML plugin descriptor '" + pluginDesc + "'."); } final Element root = document.getDocumentElement(); final String id = root.getAttribute(PLUGIN_ID_ATTR_NAME); final String name = root.getAttribute(PLUGIN_NAME_ATTR_NAME); // create plugin object and add it in the registry final PluginImpl plugin = new PluginImpl(this, pluginDesc, id, name, classLoader); final Plugin prevPlugin = registry.plugins.put(plugin.getId(), plugin); if (prevPlugin != null) { throw new CompilerError(GenericErrors.INTERNAL_ERROR, "Invalid plugin ID \"" + plugin.getId() + "\" A plugin with the same name is already defined."); } // add extension and extension points to plugin and registry final NodeList nodes = root.getChildNodes(); for (int i = 0; i < nodes.getLength(); i++) { final Node node = nodes.item(i); if (!(node instanceof Element)) continue; final Element element = (Element) node; if (element.getNodeName().equals(EXTENSION_ELEMENT_NAME)) { plugin.addExtension(new ExtensionImpl(plugin, element)); } else if (element.getNodeName().equals(EXTENSION_POINT_ELEMENT_NAME)) { final ExtensionPointImpl point = new ExtensionPointImpl(plugin, element); final ExtensionPoint prevPoint = registry.extensionPoints.put(point.getQualifiedId(), point); if (prevPoint != null) { throw new CompilerError(GenericErrors.INTERNAL_ERROR, "Invalid Extenstion point ID \"" + id + "\" An extension point with the same name is already defined."); } plugin.addExtensionPoint(point); } } } protected synchronized PluginRegistry getRegistry() { if (pluginRegistry == null) { pluginRegistry = initRegistry(); } return pluginRegistry; } protected static final class PluginRegistry { final Map<String, PluginImpl> plugins = new HashMap<String, PluginImpl>(); final Map<String, ExtensionPointImpl> extensionPoints = new HashMap<String, ExtensionPointImpl>(); } }