PrintGCStat.java

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 *
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 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
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/*
 * This source code is provided to illustrate the usage of a given feature
 * or technique and has been deliberately simplified. Additional steps
 * required for a production-quality application, such as security checks,
 * input validation and proper error handling, might not be present in
 * this sample code.
 */


/*
 */

import static java.lang.management.ManagementFactory.*;
import java.lang.management.*;
import javax.management.*;
import java.io.*;
import java.util.*;

/**
 * Example of using the java.lang.management API to monitor
 * the memory usage and garbage collection statistics.
 *
 * @author  Mandy Chung
 */
public class PrintGCStat {
    private RuntimeMXBean rmbean;
    private MemoryMXBean mmbean;
    private List<MemoryPoolMXBean> pools;
    private List<GarbageCollectorMXBean> gcmbeans;

    /**
     * Constructs a PrintGCStat object to monitor a remote JVM.
     */
    public PrintGCStat(MBeanServerConnection server) throws IOException {
        // Create the platform mxbean proxies
        this.rmbean = newPlatformMXBeanProxy(server,
                                             RUNTIME_MXBEAN_NAME,
                                             RuntimeMXBean.class);
        this.mmbean = newPlatformMXBeanProxy(server,
                                             MEMORY_MXBEAN_NAME,
                                             MemoryMXBean.class);
        ObjectName poolName = null;
        ObjectName gcName = null;
        try {
            poolName = new ObjectName(MEMORY_POOL_MXBEAN_DOMAIN_TYPE+",*");
            gcName = new ObjectName(GARBAGE_COLLECTOR_MXBEAN_DOMAIN_TYPE+",*");
        } catch (MalformedObjectNameException e) {
            // should not reach here
            assert(false);
        }

        Set<ObjectName> mbeans = server.queryNames(poolName, null);
        if (mbeans != null) {
            pools = new ArrayList<MemoryPoolMXBean>();
            for (ObjectName objName : mbeans) {
                MemoryPoolMXBean p =
                    newPlatformMXBeanProxy(server,
                                           objName.getCanonicalName(),
                                           MemoryPoolMXBean.class);
                pools.add(p);
            }
        }

        mbeans = server.queryNames(gcName, null);
        if (mbeans != null) {
            gcmbeans = new ArrayList<GarbageCollectorMXBean>();
            for (ObjectName objName : mbeans) {
                GarbageCollectorMXBean gc =
                    newPlatformMXBeanProxy(server,
                                           objName.getCanonicalName(),
                                           GarbageCollectorMXBean.class);
                gcmbeans.add(gc);
            }
        }
    }

    /**
     * Constructs a PrintGCStat object to monitor the local JVM.
     */
    public PrintGCStat() {
        // Obtain the platform mxbean instances for the running JVM.
        this.rmbean = getRuntimeMXBean();
        this.mmbean = getMemoryMXBean();
        this.pools = getMemoryPoolMXBeans();
        this.gcmbeans = getGarbageCollectorMXBeans();
    }

    /**
     * Prints the verbose GC log to System.out to list the memory usage
     * of all memory pools as well as the GC statistics.
     */
    public void printVerboseGc() {
        System.out.println("Uptime: " + formatMillis(rmbean.getUptime()));
        System.out.println("Heap usage: " + mmbean.getHeapMemoryUsage());
        System.out.println("Non-Heap memory usage: " + mmbean.getNonHeapMemoryUsage());
        for (GarbageCollectorMXBean gc : gcmbeans) {
            System.out.print(" [" + gc.getName() + ": ");
            System.out.print("Count=" + gc.getCollectionCount());
            System.out.print(" GCTime=" + formatMillis(gc.getCollectionTime()));
            System.out.print("]");
        }
        System.out.println();
        for (MemoryPoolMXBean p : pools) {
            System.out.print("  [" + p.getName() + ":");
            MemoryUsage u = p.getUsage();
            System.out.print(" Used=" + formatBytes(u.getUsed()));
            System.out.print(" Committed=" + formatBytes(u.getCommitted()));
            System.out.println("]");
        }
    }

    private String formatMillis(long ms) {
        return String.format("%.4fsec", ms / (double) 1000);
    }
    private String formatBytes(long bytes) {
        long kb = bytes;
        if (bytes > 0) {
            kb = bytes / 1024;
        }
        return kb + "K";
    }
}