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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.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.HashSet;
import java.util.Set;
import java.util.logging.Level;
import java.util.logging.Logger;
/**
* Service discovery for Tuscany based on J2SE Jar service provider spec.
* Services are described using configuration files in META-INF/services.
* Service description specifies a class name followed by optional properties.
*
*
* @version $Rev$ $Date$
*/
public class ServiceDiscovery {
private static final Logger logger = Logger.getLogger(ServiceDiscovery.class.getName());
private final static ServiceDiscovery INSTANCE = new ServiceDiscovery();
private ServiceDiscoverer discoverer;
private Set<ClassLoader> registeredClassLoaders = new HashSet<ClassLoader>();
/**
* Get an instance of Service discovery, one instance is created per
* ClassLoader that this class is loaded from
*
* @return
*/
public static ServiceDiscovery getInstance() {
return INSTANCE;
}
public ServiceDiscoverer getServiceDiscoverer() {
if (discoverer == null) {
discoverer = new ClassLoaderServiceDiscoverer();
}
return discoverer;
}
public void setServiceDiscoverer(ServiceDiscoverer sd) {
if (discoverer != null) {
throw new IllegalStateException("The ServiceDiscoverer cannot be reset");
}
discoverer = sd;
}
/**
* @deprecated
* Register a ClassLoader with this discovery mechanism. Tuscany extension
* ClassLoaders are registered here.
*
* @param classLoader
*/
@Deprecated
public synchronized void registerClassLoader(ClassLoader classLoader) {
registeredClassLoaders.add(classLoader);
}
/**
* @deprecated
* Unregister a ClassLoader with this discovery mechanism.
*
* @param classLoader
*/
@Deprecated
public synchronized void unregisterClassLoader(ClassLoader classLoader) {
registeredClassLoaders.remove(classLoader);
}
/**
* Get all service declarations for this name
*
* @param name
* @return set of service declarations
* @throws IOException
*/
public Set<ServiceDeclaration> getServiceDeclarations(String name) throws IOException {
Set<ServiceDeclaration> services = getServiceDiscoverer().discover(name, false);
return services;
}
/**
* Get all service declarations for this interface
*
* @param serviceInterface
* @return set of service declarations
* @throws IOException
*/
public Set<ServiceDeclaration> getServiceDeclarations(Class<?> serviceInterface) throws IOException {
return getServiceDeclarations(serviceInterface.getName());
}
/**
* Load one service implementation class for this interface
*
* @param serviceInterface
* @return service implementation class
* @throws IOException
* @throws ClassNotFoundException
*/
public Class<?> loadFirstServiceClass(final Class<?> serviceInterface) throws IOException, ClassNotFoundException {
// Try System property first
String className = AccessController.doPrivileged(new PrivilegedAction<String>() {
public String run() {
return System.getProperty(serviceInterface.getName());
}
});
if (className != null) {
try {
// Try the classloader for the service interface first
return Class.forName(className, false, serviceInterface.getClassLoader());
} catch (ClassNotFoundException e) {
try {
// Try the thread context classloader
return Class.forName(className, false, Thread.currentThread().getContextClassLoader());
} catch (ClassNotFoundException ex) {
logger.log(Level.WARNING, ex.getMessage(), ex);
}
}
}
Set<ServiceDeclaration> services = getServiceDiscoverer().discover(serviceInterface.getName(), true);
if (services.isEmpty()) {
return null;
}
return services.iterator().next().loadClass();
}
/**
* Create a new instance of a factory service class.
*
* @param serviceInterface
* @return service implementation class
* @throws SecurityException
* @throws NoSuchMethodException
* @throws InvocationTargetException
* @throws IllegalAccessException
*/
public Object newFactoryClassInstance(final Class<?> serviceInterface) throws SecurityException, NoSuchMethodException, InvocationTargetException, IllegalAccessException {
Method newInstanceMethod = serviceInterface.getMethod("newInstance");
Object factory = newInstanceMethod.invoke(null);
return factory;
}
}
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