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Java example source code file (ReflectionUtils.java)

This example Java source code file (ReflectionUtils.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

blocked, class, configuration, constructor, constructor_cache, error, management, map, reflection, runtimeexception, stack_depth, string, suppresswarnings, threadinfo, threading, threads, util, waited

The ReflectionUtils.java Java example source code

/*
 *
 *  * Copyright 2015 Skymind,Inc.
 *  *
 *  *    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 org.deeplearning4j.util;

import org.canova.api.conf.Configuration;

import java.io.PrintWriter;
import java.lang.management.ManagementFactory;
import java.lang.management.ThreadInfo;
import java.lang.management.ThreadMXBean;
import java.lang.reflect.Constructor;
import java.lang.reflect.Method;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

/**
 * General reflection utils
 */

public class ReflectionUtils {

    private static final Class<?>[] EMPTY_ARRAY = new Class[]{};

    /**
     * Cache of constructors for each class. Pins the classes so they
     * can't be garbage collected until ReflectionUtils can be collected.
     */
    private static final Map<Class> CONSTRUCTOR_CACHE =
            new ConcurrentHashMap<>();


    /**
     * This code is to support backward compatibility and break the compile
     * time dependency of core on mapred.
     * This should be made deprecated along with the mapred package HADOOP-1230.
     * Should be removed when mapred package is removed.
     */
    private static void setJobConf(Object theObject, Configuration conf) {
        //If JobConf and JobConfigurable are in classpath, AND
        //theObject is of type JobConfigurable AND
        //conf is of type JobConf then
        //invoke configure on theObject
        try {
            Class<?> jobConfClass =
                    conf.getClassByName("org.apache.hadoop.mapred.JobConf");
            Class<?> jobConfigurableClass =
                    conf.getClassByName("org.apache.hadoop.mapred.JobConfigurable");
            if (jobConfClass.isAssignableFrom(conf.getClass()) &&
                    jobConfigurableClass.isAssignableFrom(theObject.getClass())) {
                Method configureMethod =
                        jobConfigurableClass.getMethod("configure", jobConfClass);
                configureMethod.invoke(theObject, conf);
            }
        } catch (ClassNotFoundException e) {
            //JobConf/JobConfigurable not in classpath. no need to configure
        } catch (Exception e) {
            throw new RuntimeException("Error in configuring object", e);
        }
    }

    /** Create an object for the given class and initialize it from conf
     *
     * @param theClass class of which an object is created
     * @param conf Configuration
     * @return a new object
     */
    @SuppressWarnings("unchecked")
    public static <T> T newInstance(Class theClass, Configuration conf) {
        T result;
        try {
            Constructor<T> meth = (Constructor) CONSTRUCTOR_CACHE.get(theClass);
            if (meth == null) {
                meth = theClass.getDeclaredConstructor(EMPTY_ARRAY);
                meth.setAccessible(true);
                CONSTRUCTOR_CACHE.put(theClass, meth);
            }
            result = meth.newInstance();
        } catch (Exception e) {
            throw new RuntimeException(e);
        }

        return result;
    }

    static private ThreadMXBean threadBean =
            ManagementFactory.getThreadMXBean();

    public static void setContentionTracing(boolean val) {
        threadBean.setThreadContentionMonitoringEnabled(val);
    }

    private static String getTaskName(long id, String name) {
        if (name == null) {
            return Long.toString(id);
        }
        return id + " (" + name + ")";
    }

    /**
     * Print all of the thread's information and stack traces.
     *
     * @param stream the stream to
     * @param title a string title for the stack trace
     */
    public static void printThreadInfo(PrintWriter stream,
                                       String title) {
        final int STACK_DEPTH = 20;
        boolean contention = threadBean.isThreadContentionMonitoringEnabled();
        long[] threadIds = threadBean.getAllThreadIds();
        stream.println("Process Thread Dump: " + title);
        stream.println(threadIds.length + " active threads");
        for (long tid: threadIds) {
            ThreadInfo info = threadBean.getThreadInfo(tid, STACK_DEPTH);
            if (info == null) {
                stream.println("  Inactive");
                continue;
            }
            stream.println("Thread " +
                    getTaskName(info.getThreadId(),
                            info.getThreadName()) + ":");
            Thread.State state = info.getThreadState();
            stream.println("  State: " + state);
            stream.println("  Blocked count: " + info.getBlockedCount());
            stream.println("  Waited count: " + info.getWaitedCount());
            if (contention) {
                stream.println("  Blocked time: " + info.getBlockedTime());
                stream.println("  Waited time: " + info.getWaitedTime());
            }
            if (state == Thread.State.WAITING) {
                stream.println("  Waiting on " + info.getLockName());
            } else  if (state == Thread.State.BLOCKED) {
                stream.println("  Blocked on " + info.getLockName());
                stream.println("  Blocked by " +
                        getTaskName(info.getLockOwnerId(),
                                info.getLockOwnerName()));
            }
            stream.println("  Stack:");
            for (StackTraceElement frame: info.getStackTrace()) {
                stream.println("    " + frame.toString());
            }
        }
        stream.flush();
    }

    private static long previousLogTime = 0;


    /**
     * Return the correctly-typed {@link Class} of the given object.
     *
     * @param o object whose correctly-typed <code>Class is to be obtained
     * @return the correctly typed <code>Class of the given object.
     */
    @SuppressWarnings("unchecked")
    public static <T> Class getClass(T o) {
        return (Class<T>)o.getClass();
    }

    // methods to support testing
    static void clearCache() {
        CONSTRUCTOR_CACHE.clear();
    }

    static int getCacheSize() {
        return CONSTRUCTOR_CACHE.size();
    }




}

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