package io.coati;

import javax.management.MBeanServer;
import java.lang.management.ManagementFactory;
import com.sun.management.HotSpotDiagnosticMXBean;

public class HeapDumper {
    // This is the name of the HotSpot Diagnostic MBean
    private static final String HOTSPOT_BEAN_NAME =
         "com.sun.management:type=HotSpotDiagnostic";

    // field to store the hotspot diagnostic MBean 
    private static volatile HotSpotDiagnosticMXBean hotspotMBean;

    /*\*
     \* Call this method from your application whenever you 
     \* want to dump the heap snapshot into a file.
     \*
     \* @param fileName name of the heap dump file
     \* @param live flag that tells whether to dump
     \*             only the live objects
     \*/
    static void dumpHeap(String fileName, boolean live) {
        // initialize hotspot diagnostic MBean
        initHotspotMBean();
        try {
            hotspotMBean.dumpHeap(fileName, live);
        } catch (RuntimeException re) {
            throw re;
        } catch (Exception exp) {
            throw new RuntimeException(exp);
        }
    }

    // initialize the hotspot diagnostic MBean field
    private static void initHotspotMBean() {
        if (hotspotMBean == null) {
            synchronized (HeapDumper.class) {
                if (hotspotMBean == null) {
                    hotspotMBean = getHotspotMBean();
                }
            }
        }
    }

    // get the hotspot diagnostic MBean from the
    // platform MBean server
    private static HotSpotDiagnosticMXBean getHotspotMBean() {
        try {
            MBeanServer server = ManagementFactory.getPlatformMBeanServer();
            HotSpotDiagnosticMXBean bean = 
                ManagementFactory.newPlatformMXBeanProxy(server,
                HOTSPOT_BEAN_NAME, HotSpotDiagnosticMXBean.class);
            return bean;
        } catch (RuntimeException re) {
            throw re;
        } catch (Exception exp) {
            throw new RuntimeException(exp);
        }
    }
}