Java tutorial
/* * (C) Copyright 2006-2008 Nuxeo SAS (http://nuxeo.com/) and contributors. * * All rights reserved. This program and the accompanying materials * are made available under the terms of the GNU Lesser General Public License * (LGPL) version 2.1 which accompanies this distribution, and is available at * http://www.gnu.org/licenses/lgpl.html * * This library 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. * * Contributors: * bstefanescu */ package org.nuxeo.ecm.webengine.loader.store; import java.io.IOException; import java.net.URL; import java.util.ArrayList; import java.util.Collections; import java.util.Enumeration; import java.util.LinkedHashSet; import java.util.List; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; /** * The class loader allows modifying the stores (adding/removing). * Mutable operations are thread safe. * * @author <a href="mailto:bs@nuxeo.com">Bogdan Stefanescu</a> */ public class ResourceStoreClassLoader extends ClassLoader implements Cloneable { private final Log log = LogFactory.getLog(ResourceStoreClassLoader.class); private volatile ResourceStore[] stores; private final LinkedHashSet<ResourceStore> cp; // class path public ResourceStoreClassLoader(final ClassLoader pParent) { this(pParent, new LinkedHashSet<ResourceStore>()); } protected ResourceStoreClassLoader(final ClassLoader pParent, LinkedHashSet<ResourceStore> cp) { super(pParent); this.cp = cp; if (!cp.isEmpty()) { stores = cp.toArray(new ResourceStore[cp.size()]); } } public synchronized boolean addStore(ResourceStore store) { if (cp.add(store)) { stores = cp.toArray(new ResourceStore[cp.size()]); return true; } return false; } public synchronized boolean removeStore(ResourceStore store) { if (cp.remove(store)) { stores = cp.toArray(new ResourceStore[cp.size()]); return true; } return false; } @Override public synchronized ResourceStoreClassLoader clone() { return new ResourceStoreClassLoader(getParent(), new LinkedHashSet<ResourceStore>(cp)); } public ResourceStore[] getStores() { return stores; } protected Class<?> fastFindClass(final String name) { ResourceStore[] _stores = stores; // use a local variable if (_stores != null) { for (final ResourceStore store : _stores) { final byte[] clazzBytes = store.getBytes(convertClassToResourcePath(name)); if (clazzBytes != null) { if (log.isTraceEnabled()) { log.trace(getId() + " found class: " + name + " (" + clazzBytes.length + " bytes)"); } doDefinePackage(name); return defineClass(name, clazzBytes, 0, clazzBytes.length); } } } return null; } /** * Without this method getPackage() returns null * @param name */ protected void doDefinePackage(String name) { int i = name.lastIndexOf('.'); if (i > -1) { String pkgname = name.substring(0, i); Package pkg = getPackage(pkgname); if (pkg == null) { definePackage(pkgname, null, null, null, null, null, null, null); } } } @Override protected URL findResource(String name) { ResourceStore[] _stores = stores; // use a local variable if (_stores != null) { for (final ResourceStore store : _stores) { final URL url = store.getURL(name); if (url != null) { if (log.isTraceEnabled()) { log.trace(getId() + " found resource: " + name); } return url; } } } return null; } @Override protected Enumeration<URL> findResources(String name) throws IOException { ResourceStore[] _stores = stores; // use a local variable if (_stores != null) { List<URL> result = new ArrayList<URL>(); for (final ResourceStore store : _stores) { final URL url = store.getURL(name); if (url != null) { if (log.isTraceEnabled()) { log.trace(getId() + " found resource: " + name); } result.add(url); } } return Collections.enumeration(result); } return null; } @Override public synchronized Class<?> loadClass(String name, boolean resolve) throws ClassNotFoundException { // log.debug(getId() + " looking for: " + name); Class<?> clazz = findLoadedClass(name); if (clazz == null) { clazz = fastFindClass(name); if (clazz == null) { final ClassLoader parent = getParent(); if (parent != null) { clazz = parent.loadClass(name); // log.debug(getId() + " delegating loading to parent: " + name); } else { throw new ClassNotFoundException(name); } } else { if (log.isDebugEnabled()) { log.debug(getId() + " loaded from store: " + name); } } } if (resolve) { resolveClass(clazz); } return clazz; } @Override protected Class<?> findClass(final String name) throws ClassNotFoundException { final Class<?> clazz = fastFindClass(name); if (clazz == null) { throw new ClassNotFoundException(name); } return clazz; } @Override public Enumeration<URL> getResources(String name) throws IOException { Enumeration<URL> urls = findResources(name); if (urls == null) { final ClassLoader parent = getParent(); if (parent != null) { urls = parent.getResources(name); } } return urls; } @Override public URL getResource(String name) { URL url = findResource(name); if (url == null) { final ClassLoader parent = getParent(); if (parent != null) { url = parent.getResource(name); } } return url; } //TODO implement this method if you want packages to be supported by this loader @Override protected Package getPackage(String name) { return super.getPackage(name); } @Override protected Package[] getPackages() { return super.getPackages(); } protected String getId() { return "" + this + "[" + this.getClass().getClassLoader() + "]"; } /** * org.my.Class -> org/my/Class.class */ public static String convertClassToResourcePath(final String pName) { return pName.replace('.', '/') + ".class"; } }