从运行的JVM收集统计信息的API

Question

对于一个类项目，我想实现一个Java应用程序，该应用程序连接到本地JVM并收集统计信息，例如堆使用情况，线程数，已加载的类等。我已经在网上搜索API，内置第三方，这将允许我执行此操作，但到目前为止我一直没有成功。

有谁知道一个API，它将允许我连接到正在运行的JVM并收集统计信息？

Answer 1

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.jarJDK的手动添加到类路径。在模块化软件中，您必须向jdk.attach模块添加依赖项。

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 code
  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上述解决方案的方法需要Java8。较旧的Java版本的替代方案如下所示：

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();
}