java - 用于从运行中的 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，它连接到本地 JVM 并收集堆使用情况、线程数、加载的类等统计信息。我在网上搜索了一个 API，第三方内置的，这将允许我这样做，但到目前为止我还没有成功。

有谁知道可以让我连接到正在运行的 JVM 并收集统计信息的 API？

Answer 1

以下类演示了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(这通过 JVM 连接工作，无需 JMX)和内存使用情况。使用其他 MXBean 类型很容易扩展以打印其他统计信息。

请注意，在 Java 9 之前，您必须手动将 JDK 的 tools.jar 添加到类路径中。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());
  }
}

上述解决方案的 connect 方法需要 Java 8。旧 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();
}