通过jvm api实现从外部对java程序作gc垃圾回收

       为了实现程序中内存的自动回收，java虚拟机可谓想尽了办法，但如果java程序总是无羞耻的去申请临时内存，那么java的垃圾回收是不是有点尴尬，分的少把，回收频率过快，有可能出现内存不足，分的多把，又是白白浪费内存，这实在有点让人疑惑。

        有时候定时的从外部去申请做gc垃圾回收，还是有必要的，好在java工具强大的一塌糊涂，通过jvm api可以轻易实现, 直接上代码测试吧，依赖jdk-devel包中的tools.jar。

import java.lang.System;

import java.io.*;

import java.util.*;

import com.sun.tools.attach.AgentInitializationException;

import com.sun.tools.attach.AgentLoadException;

import com.sun.tools.attach.VirtualMachineDescriptor;

import com.sun.tools.attach.VirtualMachine;

import com.sun.tools.attach.*;

import javax.management.remote.JMXServiceURL;

import javax.management.remote.*;

import java.lang.management.MemoryMXBean;

import java.lang.management.ManagementFactory;

class Test{

    public Test(){

    }

public static void main(String[] args) throws Exception {

        List<VirtualMachineDescriptor> list = VirtualMachine.list();

        for (VirtualMachineDescriptor vmd : list)

        {

                System.out.println("pid:" + vmd.id() + ":" + vmd.displayName());

        }

        System.out.println(args[0]);

        VirtualMachine virtualmachine = VirtualMachine.attach(args[0]);

        String javaHome = virtualmachine.getSystemProperties().getProperty("java.home");

        String jmxAgent = javaHome + File.separator + "lib" + File.separator + "management-agent.jar";

        System.out.println(jmxAgent);

        virtualmachine.loadAgent(jmxAgent, "com.sun.management.jmxremote");

        Properties properties = virtualmachine.getAgentProperties();

        String address = (String)properties.get("com.sun.management.jmxremote.localConnectorAddress");

        System.out.println(address);

        virtualmachine.detach();

        JMXServiceURL url = new JMXServiceURL(address);

        JMXConnector connector = JMXConnectorFactory.connect(url);

        MemoryMXBean mxb = ManagementFactory.newPlatformMXBeanProxy(connector.getMBeanServerConnection(), "java.lang:type=Memory",MemoryMXBean.class);

        mxb.gc();

}

       参考资料：
java management api