Java tutorial
/** * $Id$ * * Gasp: Generic Application Service Platform * http://gasp.berlios.de * Copyright (c) 2005 Gasp team * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 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 General Public License for more details. * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */ package org.eu.gasp.core.internal; import java.io.File; import java.net.URL; import java.net.URLDecoder; import java.util.ArrayList; import java.util.Iterator; import java.util.LinkedHashMap; import java.util.List; import java.util.Map; import java.util.jar.Attributes; import java.util.jar.JarFile; import java.util.jar.Manifest; import org.apache.commons.lang.StringUtils; import org.eu.gasp.core.Plugin; import org.eu.gasp.core.PluginContext; import org.eu.gasp.core.PluginDescriptor; import org.eu.gasp.core.Version; import org.eu.gasp.core.util.ReversedIterator; public class DefaultPluginRegistry extends AbstractPluginRegistry { private static final String JAR_PLUGIN_CLASS = "Plugin-Class"; private static final String JAR_PLUGIN_VERSION = "Plugin-Version"; private static final String JAR_PLUGIN = "Plugin"; private static final String JAR_PLUGIN_REQUIRES = "Plugin-Requires"; private static final String JAR_PLUGIN_PROVIDES = "Plugin-Provides"; private final Map<PluginDescriptor, PluginData> plugins = new LinkedHashMap<PluginDescriptor, PluginData>(); public ClassLoader getClassLoader(String pluginId, Version version) { if (StringUtils.isBlank(pluginId)) { throw new IllegalArgumentException("pluginId"); } final PluginDescriptor pluginDescriptor = getPluginDescriptor(pluginId, version); return plugins.get(pluginDescriptor).classLoader; } @Override protected void doActivate(String id, Version version) throws Exception { final PluginDescriptor pd = getPluginDescriptor(id, version); log.info("Activating plugin: " + pd); // TODO handle dependencies getPlugin(pd).start(plugins.get(pd).pluginContext); } @Override protected void doDeactivate(String id, Version version) throws Exception { final PluginDescriptor pd = getPluginDescriptor(id, version); // TODO handle dependencies final PluginData pluginData = plugins.get(pd); if (pluginData.plugin == null) { return; } log.info("Deactivating plugin: " + pd); pluginData.plugin.stop(pluginData.pluginContext); pluginData.clear(); } @Override protected void doInstall(URL url) throws Exception { // right now, we only handle the "file" protocol: // we may support more protocols in the future // (like remote plugin locations with automatic download) final String protocol = url.getProtocol(); if ("file".equals(protocol)) { // we have to transform the URL encoded file: // %20 = whitespace... and so on final File file = new File(URLDecoder.decode(url.getFile(), "UTF-8")); registerPlugin(file); } else { throw new IllegalStateException("Unhandled protocol: " + protocol); } } @Override protected void doShutdown() throws Exception { for (final Iterator<PluginDescriptor> i = new ReversedIterator<PluginDescriptor>( plugins.keySet().iterator()); i.hasNext();) { final PluginDescriptor pluginDescriptor = i.next(); try { deactivate(pluginDescriptor.getId(), pluginDescriptor.getVersion()); } catch (Exception e) { log.error("Error while stopping plugin: " + pluginDescriptor); } } } private PluginDescriptor getPluginDescriptor(String pluginId, Version version) { if (StringUtils.isBlank(pluginId)) { throw new IllegalArgumentException("pluginId"); } PluginDescriptor mostUpToDatePluginDescriptor = null; for (final Map.Entry<PluginDescriptor, PluginData> entry : plugins.entrySet()) { if (!pluginId.equals(entry.getKey().getId())) { continue; } if (version != null && entry.getKey().getVersion().equals(version)) { return entry.getKey(); } else if (mostUpToDatePluginDescriptor == null || entry.getKey().getVersion().compareTo(mostUpToDatePluginDescriptor.getVersion()) > -1) { mostUpToDatePluginDescriptor = entry.getKey(); } } if (version == null && mostUpToDatePluginDescriptor != null) { return mostUpToDatePluginDescriptor; } throw new IllegalStateException("Plugin not found: " + pluginId + (version != null ? "-" + version : "")); } private void registerPlugin(File file) throws Exception { if (isFileRegistered(file)) { return; } final JarFile jarFile = new JarFile(file); final Manifest manifest = jarFile.getManifest(); String pluginId = null; String pluginClassName = null; Version version = null; final List<DefaultPluginDependency> pluginDependencies = new ArrayList<DefaultPluginDependency>(); final List<String> services = new ArrayList<String>(); final Attributes attrs = manifest.getMainAttributes(); for (final Map.Entry entry : attrs.entrySet()) { final String key = entry.getKey().toString(); final String value = StringUtils.trimToNull(entry.getValue().toString()); if (value == null) { continue; } if (JAR_PLUGIN.equals(key)) { pluginId = value; } else if (JAR_PLUGIN_CLASS.equals(key)) { pluginClassName = value; } else if (JAR_PLUGIN_VERSION.equals(key)) { version = new Version(value); } else if (JAR_PLUGIN_PROVIDES.equals(key)) { for (final String service : value.split(",")) { services.add(service); } } else if (JAR_PLUGIN_REQUIRES.equals(key)) { for (final String versionnedRequiredPluginId : value.split(",")) { pluginDependencies.add(new DefaultPluginDependency(versionnedRequiredPluginId, null)); } } } if (StringUtils.isBlank(pluginId)) { throw new IllegalStateException("Missing " + JAR_PLUGIN + " attribute in manifest"); } if (version == null) { throw new IllegalStateException("Missing " + JAR_PLUGIN_VERSION + " attribute in manifest"); } final PluginDescriptor pluginDescriptor = new DefaultPluginDescriptor(pluginId, version, pluginClassName, pluginDependencies, services); if (!plugins.containsKey(pluginDescriptor)) { log.info("Registering plugin: " + pluginDescriptor); plugins.put(pluginDescriptor, new PluginData(file)); } } @Override protected PluginDescriptor doGetPluginDescriptor(Plugin plugin, Version version) throws Exception { if (plugin == null) { throw new NullPointerException("plugin"); } PluginDescriptor mostUpToDatePluginDescriptor = null; for (final Map.Entry<PluginDescriptor, PluginData> entry : plugins.entrySet()) { if (!plugin.equals(entry.getValue().plugin)) { continue; } if (version != null && entry.getKey().getVersion().equals(version)) { return entry.getKey(); } else if (mostUpToDatePluginDescriptor == null || entry.getKey().getVersion().compareTo(mostUpToDatePluginDescriptor.getVersion()) > -1) { mostUpToDatePluginDescriptor = entry.getKey(); } } if (version == null && mostUpToDatePluginDescriptor != null) { return mostUpToDatePluginDescriptor; } throw new IllegalStateException("Plugin not found: " + plugin + (version != null ? "-" + version : "")); } private boolean isFileRegistered(File file) { if (file == null) { throw new NullPointerException("file"); } for (final PluginData pluginData : plugins.values()) { if (file.equals(pluginData.file)) { return true; } } return false; } private Plugin getPlugin(PluginDescriptor pd) { final PluginData pluginData = plugins.get(pd); Plugin plugin = pluginData.plugin; if (plugin == null) { try { final PluginClassLoader classLoader = new PluginClassLoader(this, pd, pluginData.file.toURI().toURL(), getClass().getClassLoader()); plugin = (Plugin) classLoader.loadClass(pd.getPluginClassName()).newInstance(); pluginData.plugin = plugin; pluginData.classLoader = classLoader; pluginData.pluginContext = new DefaultPluginContext(pd); } catch (Exception e) { throw new IllegalStateException("Unable to instanciate plugin: " + pd.getPluginClassName(), e); } } return plugin; } private class PluginData { final File file; Plugin plugin; ClassLoader classLoader; PluginContext pluginContext; public PluginData(final File file) { this.file = file; } public void clear() { plugin = null; classLoader = null; pluginContext = null; } } }