从运行的JVM收集统计信息的API

下列类演示如何连接到正在运行的JVM并建立JMX连接，并在必要时加载JMX代理。它将使用MemoryMXBean打印系统属性（无需JMX即可通过JVM连接工作）和内存使用情况。使用其他MXBean类型进行扩展以打印其他统计信息很容易。

请注意，在Java 9之前，您必须将

tools.jar

jdk.attach

import static java.lang.management.ManagementFactory.MEMORY_MXBEAN_NAME;import static java.lang.management.ManagementFactory.newPlatformMXBeanProxy;import java.io.*;import java.lang.management.MemoryMXBean;import java.lang.management.MemoryUsage;import java.util.*;import javax.management.MBeanServerConnection;import javax.management.remote.JMXConnector;import javax.management.remote.JMXConnectorFactory;import javax.management.remote.JMXServiceURL;import com.sun.tools.attach.*;public class CmdLineTool{  static final String CONNECTOR_ADDRESS =      "com.sun.management.jmxremote.localConnectorAddress";  public static void main(String[] args)  {    if(args.length!=1)      System.err.println("Usage: java CmdLineTool <pid>");    else if(printStats(args[0])) return;    System.out.println("Currently running");    for(VirtualMachineDescriptor vmd:VirtualMachine.list())      System.out.println(vmd.id()+"t"+vmd.displayName());  }  private static boolean printStats(String id)  {    try    {      VirtualMachine vm=VirtualMachine.attach(id);      System.out.println("Connected to "+vm.id());      System.out.println("System Properties:");      for(Map.Entry<?,?> en:vm.getSystemProperties().entrySet())        System.out.println("t"+en.getKey()+" = "+en.getValue());      System.out.println();      try      {        MBeanServerConnection sc=connect(vm);        MemoryMXBean memoryMXBean =          newPlatformMXBeanProxy(sc, MEMORY_MXBEAN_NAME, MemoryMXBean.class);        getRamInfoHtml(memoryMXBean);      } catch(IOException ex)      {        System.out.println("JMX: "+ex);      }      vm.detach();      return true;    } catch(AttachNotSupportedException | IOException ex)    {      ex.printStackTrace();    }    return false;  }  // requires Java 8, alternative below the pre  static MBeanServerConnection connect(VirtualMachine vm) throws IOException  {    String connectorAddress = vm.startLocalManagementAgent();    JMXConnector c=JMXConnectorFactory.connect(new JMXServiceURL(connectorAddress));    return c.getMBeanServerConnection();  }  static void getRamInfoHtml(MemoryMXBean memoryMXBean)  {    System.out.print("Heap:t");    MemoryUsage mu=memoryMXBean.getHeapMemoryUsage();    System.out.println(      "allocated "+mu.getCommitted()+", used "+mu.getUsed()+", max "+mu.getMax());    System.out.print("Non-Heap:t");    mu=memoryMXBean.getNonHeapMemoryUsage();    System.out.println(      "allocated "+mu.getCommitted()+", used "+mu.getUsed()+", max "+mu.getMax());    System.out.println(      "Pending Finalizations: "+memoryMXBean.getObjectPendingFinalizationCount());  }}

connect

static MBeanServerConnection connect(VirtualMachine vm) throws IOException{  String connectorAddress = vm.getAgentProperties().getProperty(CONNECTOR_ADDRESS);  if(connectorAddress == null)  {    System.out.println("loading agent");    Properties props = vm.getSystemProperties();    String home  = props.getProperty("java.home");    String agent = home+File.separator+"lib"+File.separator+"management-agent.jar";    try {      vm.loadAgent(agent);    } catch (AgentLoadException|AgentInitializationException ex) {      throw new IOException(ex);    }    connectorAddress = vm.getAgentProperties().getProperty(CONNECTOR_ADDRESS);    while(connectorAddress==null) try {      Thread.sleep(1000);      connectorAddress = vm.getAgentProperties().getProperty(CONNECTOR_ADDRESS);    } catch(InterruptedException ex){}  }  JMXConnector c=JMXConnectorFactory.connect(new JMXServiceURL(connectorAddress));  return c.getMBeanServerConnection();}