org.apache.stratos.cartridge.agent.statistics.publisher.PluginLoader.java Source code

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Here is the source code for org.apache.stratos.cartridge.agent.statistics.publisher.PluginLoader.java

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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.stratos.cartridge.agent.statistics.publisher;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import java.io.File;
import java.io.IOException;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.Enumeration;
import java.util.LinkedList;
import java.util.List;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;
import java.util.zip.ZipEntry;

public class PluginLoader {
    private static final Log log = LogFactory.getLog(PluginLoader.class);

    /* Built-in plugins are listed here. This is just easier than adding this
     * jar to the list of jars to search, as it contains too much random stuff,
     * including stuff with unsatisfied dependencies that we otherwise wouldn't
     * load. There's a nice looking library called Reflections on Google Code
     * that would probably be OK, but it's more logic.
     */

    public static List<Class> loadPluginClassesFromJar(File jarPath, Class pluginInterface) {
        List<Class> listeners = new LinkedList<Class>();

        try {
            URLClassLoader loader = new URLClassLoader(new URL[] { jarPath.toURI().toURL() });
            JarFile jar = new JarFile(jarPath);
            Enumeration<? extends JarEntry> jarEnum = jar.entries();

            log.trace("Scanning jar file " + jarPath);

            while (jarEnum.hasMoreElements()) {
                ZipEntry zipEntry = jarEnum.nextElement();
                String fileName = zipEntry.getName();

                if (fileName.endsWith(".class")) {
                    log.trace("Considering jar entry " + fileName);
                    try {
                        String className = fileName.replace(".class", "").replace("/", ".");
                        Class cls = loader.loadClass(className);
                        log.trace("Loaded class " + className);

                        if (hasInterface(cls, pluginInterface)) {
                            log.trace("Class has " + pluginInterface.getName() + " interface; adding ");
                            listeners.add(cls);
                        }
                    } catch (ClassNotFoundException e) {
                        log.error("Unable to load class from " + fileName + " in " + jarPath);
                    }
                }
            }

        } catch (IOException e) {
            log.error("Unable to open JAR file " + jarPath, e);
        }

        return listeners;
    }

    private static boolean hasInterface(Class cls, Class iface) {
        for (Class in : cls.getInterfaces()) {
            if (in == iface) {
                return true;
            }
        }
        return false;
    }
}