/*
* Copyright 2014 NAVER Corp.
*
* Licensed 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 com.navercorp.pinpoint.common.plugin;
import java.net.URL;
import java.net.URLClassLoader;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.ArrayList;
import java.util.List;
import java.util.ServiceLoader;
/**
* TODO Loading all plugins with a single class loader could cause class collisions.
* Also, with current implementation, plugins can use dependencies by putting them in the plugin directory too.
* But it can lead to dependency collision between plugins because they are loaded by a single class loader.
*
* How can we prevent this?
* A ClassLoader per plugin could do it but then we have to create "N of target class loader" x "N of plugin" class loaders.
* It seems too much. For now, Just leave it as it is.
*
*
* @author Jongho Moon <jongho.moon@navercorp.com>
* @author emeroad
*
* @param <T>
*/
public class PluginLoader {
private static final SecurityManager SECURITY_MANAGER = System.getSecurityManager();
public static <T> List<T> load(Class<T> serviceType, URL[] urls) {
URLClassLoader classLoader = createPluginClassLoader(urls, ClassLoader.getSystemClassLoader());
return load(serviceType, classLoader);
}
private static PluginLoaderClassLoader createPluginClassLoader(final URL[] urls, final ClassLoader parent) {
if (SECURITY_MANAGER != null) {
return AccessController.doPrivileged(new PrivilegedAction<PluginLoaderClassLoader>() {
public PluginLoaderClassLoader run() {
return new PluginLoaderClassLoader(urls, parent);
}
});
} else {
return new PluginLoaderClassLoader(urls, parent);
}
}
public static <T> List<T> load(Class<T> serviceType, ClassLoader classLoader) {
ServiceLoader<T> serviceLoader = ServiceLoader.load(serviceType, classLoader);
List<T> plugins = new ArrayList<T>();
for (T plugin : serviceLoader) {
plugins.add(serviceType.cast(plugin));
}
return plugins;
}
}