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/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package org.apache.tuscany.sca.extensibility;
import java.io.IOException;
import java.net.URL;
import java.security.PrivilegedAction;
import java.security.PrivilegedActionException;
import java.security.PrivilegedExceptionAction;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Enumeration;
import java.util.List;
import org.apache.tuscany.sca.extensibility.impl.ClassLoaderDelegate;
/**
* A utility that controls context class loaders
* @tuscany.spi.extension.asclient
*/
public class ClassLoaderContext {
private ClassLoader classLoader;
/**
* Create a context with the parent classloader and a list of service types that can be discovered
* by the {@link ServiceDiscovery}
* @param parent
* @param discovery
* @param serviceTypes
*/
public ClassLoaderContext(ClassLoader parent, ServiceDiscovery discovery, Class... serviceTypes) {
this(parent, getClassLoaders(discovery, serviceTypes));
}
private ClassLoaderContext(ClassLoader parent, List delegates) {
List loaders = new ArrayList(delegates);
loaders.remove(parent);
if (delegates.isEmpty()) {
classLoader = parent;
} else {
classLoader = new ClassLoaderDelegate(parent, loaders);
}
}
/**
* Create a context that is visible to the parent classloader as well as the list of classloaders
* @param parent
* @param delegates
*/
public ClassLoaderContext(ClassLoader parent, ClassLoader... delegates) {
this(parent, Arrays.asList(delegates));
}
/**
* Create a context with the parent classloader and a list of service types that can be discovered
* by the {@link ServiceDiscovery}
* @param parent
* @param discovery
* @param serviceTypes
*/
public ClassLoaderContext(ClassLoader parent, ServiceDiscovery discovery, String... serviceTypes) {
this(parent, getClassLoaders(discovery, serviceTypes));
}
public T doPrivileged(PrivilegedAction action) {
ClassLoader tccl = Thread.currentThread().getContextClassLoader();
if (tccl != classLoader) {
Thread.currentThread().setContextClassLoader(classLoader);
}
try {
return action.run();
} finally {
if (tccl != classLoader) {
Thread.currentThread().setContextClassLoader(tccl);
}
}
}
public T doPrivileged(PrivilegedExceptionAction action) throws PrivilegedActionException {
ClassLoader tccl = Thread.currentThread().getContextClassLoader();
if (tccl != classLoader) {
Thread.currentThread().setContextClassLoader(classLoader);
}
try {
return action.run();
} catch (Exception e) {
throw new PrivilegedActionException(e);
} finally {
if (tccl != classLoader) {
Thread.currentThread().setContextClassLoader(tccl);
}
}
}
/**
* Set the thread context classloader (TCCL) to a classloader that delegates to a collection
* of classloaders
* @param parent The parent classloader
* @param delegates A list of classloaders to try
* @return The existing TCCL
*/
public static ClassLoader setContextClassLoader(ClassLoader parent, ClassLoader... delegates) {
ClassLoaderContext context = new ClassLoaderContext(parent, delegates);
return context.setContextClassLoader();
}
/**
* Set the context classloader so that it can access the list of service providers
* @param parent The parent classloader
* @param serviceNames A list of service provider names
* @return The old TCCL if a new one is set, otherwise null
*/
public static ClassLoader setContextClassLoader(ClassLoader parent,
ServiceDiscovery discovery,
String... serviceNames) {
ClassLoaderContext context = new ClassLoaderContext(parent, discovery, serviceNames);
return context.setContextClassLoader();
}
/**
* Set the context classloader so that it can access the list of service providers
* @param parent The parent classloader
* @param serviceNames A list of service provider names
* @return The old TCCL if a new one is set, otherwise null
*/
public static ClassLoader setContextClassLoader(ClassLoader parent,
ServiceDiscovery discovery,
Class... serviceTypes) {
ClassLoaderContext context = new ClassLoaderContext(parent, discovery, serviceTypes);
return context.setContextClassLoader();
}
public ClassLoader setContextClassLoader() {
ClassLoader tccl = Thread.currentThread().getContextClassLoader();
if (tccl != classLoader) {
Thread.currentThread().setContextClassLoader(classLoader);
return tccl;
} else {
return null;
}
}
private static ClassLoader getClassLoader(ServiceDiscovery discovery, String serviceProvider) {
try {
ServiceDeclaration sd = discovery.getServiceDeclaration(serviceProvider);
if (sd != null) {
try {
if (sd.loadClass() != null) {
return sd.loadClass().getClassLoader();
} else {
return new ClassLoaderImpl(sd);
}
} catch (ClassNotFoundException e) {
return new ClassLoaderImpl(sd);
}
}
} catch (Exception e) {
// Ignore
}
return null;
}
private static List getClassLoaders(ServiceDiscovery discovery, String... serviceNames) {
List loaders = new ArrayList();
for (String sp : serviceNames) {
ClassLoader loader = getClassLoader(discovery, sp);
if (loader != null) {
if (!loaders.contains(loader)) {
loaders.add(loader);
}
}
}
ClassLoader tccl = discovery.getContextClassLoader();
if (!loaders.contains(tccl)) {
loaders.add(tccl);
}
return loaders;
}
private static ClassLoader getClassLoader(ServiceDiscovery discovery, Class serviceType) {
try {
ServiceDeclaration sd = discovery.getServiceDeclaration(serviceType);
if (sd != null) {
return sd.loadClass().getClassLoader();
}
} catch (Exception e) {
// Ignore
}
return null;
}
private static List getClassLoaders(ServiceDiscovery discovery, Class... serviceTypes) {
List loaders = new ArrayList();
for (Class serviceType : serviceTypes) {
ClassLoader classLoader = getClassLoader(discovery, serviceType);
if (classLoader != null && !loaders.contains(classLoader)) {
loaders.add(classLoader);
}
}
ClassLoader tccl = discovery.getContextClassLoader();
if (!loaders.contains(tccl)) {
loaders.add(tccl);
}
return loaders;
}
public ClassLoader getClassLoader() {
return classLoader;
}
private static class ClassLoaderImpl extends ClassLoader {
private final ServiceDeclaration sd;
public ClassLoaderImpl(ServiceDeclaration sd) {
super();
this.sd = sd;
}
@Override
protected Class findClass(String name) throws ClassNotFoundException {
return sd.loadClass(name);
}
@Override
protected URL findResource(String name) {
return sd.getResource(name);
}
@Override
protected Enumeration findResources(String name) throws IOException {
return sd.getResources(name);
}
}
}
