org.apache.hadoop.hive.common.JavaUtils.java Source code

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Here is the source code for org.apache.hadoop.hive.common.JavaUtils.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.hadoop.hive.common;

import java.io.ByteArrayOutputStream;
import java.io.Closeable;
import java.io.IOException;
import java.io.PrintStream;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.net.URLClassLoader;
import java.util.Arrays;

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

/**
 * Collection of Java class loading/reflection related utilities common across
 * Hive.
 */
public final class JavaUtils {

    private static final Log LOG = LogFactory.getLog(JavaUtils.class);
    private static final Method SUN_MISC_UTIL_RELEASE;

    static {
        if (Closeable.class.isAssignableFrom(URLClassLoader.class)) {
            SUN_MISC_UTIL_RELEASE = null;
        } else {
            Method release = null;
            try {
                Class<?> clazz = Class.forName("sun.misc.ClassLoaderUtil");
                release = clazz.getMethod("releaseLoader", URLClassLoader.class);
            } catch (Exception e) {
                // ignore
            }
            SUN_MISC_UTIL_RELEASE = release;
        }
    }

    /**
     * Standard way of getting classloader in Hive code (outside of Hadoop).
     * 
     * Uses the context loader to get access to classpaths to auxiliary and jars
     * added with 'add jar' command. Falls back to current classloader.
     * 
     * In Hadoop-related code, we use Configuration.getClassLoader().
     */
    public static ClassLoader getClassLoader() {
        ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
        if (classLoader == null) {
            classLoader = JavaUtils.class.getClassLoader();
        }
        return classLoader;
    }

    public static Class loadClass(String className) throws ClassNotFoundException {
        return loadClass(className, true);
    }

    public static Class loadClass(String className, boolean init) throws ClassNotFoundException {
        return Class.forName(className, init, getClassLoader());
    }

    public static boolean closeClassLoadersTo(ClassLoader current, ClassLoader stop) {
        if (!isValidHierarchy(current, stop)) {
            return false;
        }
        for (; current != null && current != stop; current = current.getParent()) {
            try {
                closeClassLoader(current);
            } catch (IOException e) {
                LOG.info("Failed to close class loader " + current
                        + Arrays.toString(((URLClassLoader) current).getURLs()), e);
            }
        }
        return true;
    }

    // check before closing loaders, not to close app-classloader, etc. by mistake
    private static boolean isValidHierarchy(ClassLoader current, ClassLoader stop) {
        if (current == null || stop == null || current == stop) {
            return false;
        }
        for (; current != null && current != stop; current = current.getParent()) {
        }
        return current == stop;
    }

    // best effort to close
    // see https://issues.apache.org/jira/browse/HIVE-3969 for detail
    public static void closeClassLoader(ClassLoader loader) throws IOException {
        if (loader instanceof Closeable) {
            ((Closeable) loader).close();
        } else if (SUN_MISC_UTIL_RELEASE != null && loader instanceof URLClassLoader) {
            PrintStream outputStream = System.out;
            ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
            PrintStream newOutputStream = new PrintStream(byteArrayOutputStream);
            try {
                // SUN_MISC_UTIL_RELEASE.invoke prints to System.out
                // So we're changing the outputstream for that call,
                // and setting it back to original System.out when we're done
                System.setOut(newOutputStream);
                SUN_MISC_UTIL_RELEASE.invoke(null, loader);
                String output = byteArrayOutputStream.toString("UTF8");
                LOG.debug(output);
            } catch (InvocationTargetException e) {
                if (e.getTargetException() instanceof IOException) {
                    throw (IOException) e.getTargetException();
                }
                throw new IOException(e.getTargetException());
            } catch (Exception e) {
                throw new IOException(e);
            } finally {
                System.setOut(outputStream);
                newOutputStream.close();
            }
        }
        LogFactory.release(loader);
    }

    /**
     * Utility method for ACID to normalize logging info
     * @param extLockId LockResponse.lockid
     */
    public static String lockIdToString(long extLockId) {
        return "lockid:" + extLockId;
    }

    private JavaUtils() {
        // prevent instantiation
    }
}