jstorm-core/src/main/java/backtype/storm/utils/WorkerClassLoader.java

/**
 * 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 backtype.storm.utils;

import java.net.URL;
import java.net.URLClassLoader;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class WorkerClassLoader extends URLClassLoader {

    public static Logger LOG = LoggerFactory.getLogger(WorkerClassLoader.class);

    private ClassLoader defaultClassLoader;

    private ClassLoader JDKClassLoader;

    private boolean isDebug;

    protected static WorkerClassLoader instance;

    protected static boolean enable;

    protected static Map<Thread, ClassLoader> threadContextCache;

    protected WorkerClassLoader(URL[] urls, ClassLoader defaultClassLoader, ClassLoader JDKClassLoader, boolean isDebug) {
        super(urls, JDKClassLoader);
        this.defaultClassLoader = defaultClassLoader;
        this.JDKClassLoader = JDKClassLoader;
        this.isDebug = isDebug;

        // TODO Auto-generated constructor stub
    }

    // for all log go through logback when enable classloader
    protected boolean isLogByDefault(String name) {
        if (name.startsWith("org.apache.log4j")) {
            return true;
        } else if (name.startsWith("org.slf4j")) {
            return true;
        }

        return false;

    }

    protected boolean isLoadByDefault(String name) {
        if (name.startsWith("backtype.storm") == true) {
            return true;
        } else if (name.startsWith("com.alibaba.jstorm")) {
            return true;
        } else if (isLogByDefault(name)) {
            return true;
        } else {
            return false;
        }
    }

    @Override
    public Class<?> loadClass(String name) throws ClassNotFoundException {
        Class<?> result = null;
        try {
            result = this.findLoadedClass(name);

            if (result != null) {
                return result;
            }

            try {
                result = JDKClassLoader.loadClass(name);
                if (result != null)
                    return result;
            } catch (Exception e) {

            }

            try {
                if (isLoadByDefault(name) == false) {
                    result = findClass(name);

                    if (result != null) {
                        return result;
                    }
                }

            } catch (Exception e) {

            }

            result = defaultClassLoader.loadClass(name);
            return result;

        } finally {
            if (result != null) {
                ClassLoader resultClassLoader = result.getClassLoader();
                LOG.info("Successfully load class " + name + " by " + resultClassLoader + ",threadContextLoader:"
                        + Thread.currentThread().getContextClassLoader());
            } else {
                LOG.warn("Failed to load class " + name + ",threadContextLoader:" + Thread.currentThread().getContextClassLoader());
            }

            if (isDebug) {
                LOG.info(Utils.printStack());
            }
        }

    }

    public static WorkerClassLoader mkInstance(URL[] urls, ClassLoader DefaultClassLoader, ClassLoader JDKClassLoader, boolean enable, boolean isDebug) {
        WorkerClassLoader.enable = enable;
        if (enable == false) {
            LOG.info("Don't enable UserDefine ClassLoader");
            return null;
        }

        synchronized (WorkerClassLoader.class) {
            if (instance == null) {
                instance = new WorkerClassLoader(urls, DefaultClassLoader, JDKClassLoader, isDebug);

                threadContextCache = new ConcurrentHashMap<Thread, ClassLoader>();
            }

        }

        LOG.info("Successfully create classloader " + mk_list(urls));
        return instance;
    }

    public static WorkerClassLoader getInstance() {
        return instance;
    }

    public static boolean isEnable() {
        return enable;
    }

    public static void switchThreadContext() {
        if (enable == false) {
            return;
        }

        Thread thread = Thread.currentThread();
        ClassLoader oldClassLoader = thread.getContextClassLoader();
        threadContextCache.put(thread, oldClassLoader);
        thread.setContextClassLoader(instance);
    }

    public static void restoreThreadContext() {
        if (enable == false) {
            return;
        }

        Thread thread = Thread.currentThread();
        ClassLoader oldClassLoader = threadContextCache.get(thread);
        if (oldClassLoader != null) {
            thread.setContextClassLoader(oldClassLoader);
        } else {
            LOG.info("No context classloader of " + thread.getName());
        }
    }

    private static <V> List<V> mk_list(V... args) {
        ArrayList<V> rtn = new ArrayList<V>();
        for (V o : args) {
            rtn.add(o);
        }
        return rtn;
    }
}