为Dynamic Web Project 项目创建定时任务

一、创建Dynamic Web Project项目

创建Dynamic Web Project项目时，请同时生成web.xml文件。

二、在web.xml中加入如下内容

   

   
    
        com.tom.core.task.MemoryTask
   

三、创建MemoryTask.java类

注意：参照上面，路径应该是src\com\tom\core\task\MemoryTask.java

package com.tom.core.task;

import java.lang.management.ManagementFactory;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

import org.springframework.stereotype.Component;

import com.sun.management.OperatingSystemMXBean;

/*这里由web.xml中

com.tom.core.task.MemoryTask

指定这里的定时任务*/
@Component
public class MemoryTask implements ServletContextListener {
    @Override
    public void contextInitialized(ServletContextEvent sce) {
        Runnable runnable = new Runnable() {
            public void run() {
                // 虚拟机级内存情况查询
                long vmFree = 0;
                long vmUse = 0;
                long vmTotal = 0;
                long vmMax = 0;
                int byteToMb = 1024 * 1024;
                Runtime rt = Runtime.getRuntime();
                vmTotal = rt.totalMemory() / byteToMb;
                vmFree = rt.freeMemory() / byteToMb;
                vmMax = rt.maxMemory() / byteToMb;
                vmUse = vmTotal - vmFree;
                System.out.println("JVM内存已用的空间为：" + vmUse + " MB");
                System.out.println("JVM内存的空闲空间为：" + vmFree + " MB");
                System.out.println("JVM总内存空间为：" + vmTotal + " MB");
                System.out.println("JVM最大内存空间为：" + vmMax + " MB");

                System.out.println("======================================");
                // 操作系统级内存情况查询
                OperatingSystemMXBean osmxb = (OperatingSystemMXBean) ManagementFactory.getOperatingSystemMXBean();
                String os = System.getProperty("os.name");
                long physicalFree = osmxb.getFreePhysicalMemorySize() / byteToMb;
                long physicalTotal = osmxb.getTotalPhysicalMemorySize() / byteToMb;
                long physicalUse = physicalTotal - physicalFree;
                System.out.println("操作系统的版本：" + os);
                System.out.println("操作系统物理内存已用的空间为：" + physicalFree + " MB");
                System.out.println("操作系统物理内存的空闲空间为：" + physicalUse + " MB");
                System.out.println("操作系统总物理内存：" + physicalTotal + " MB");

                // 获得线程总数
                ThreadGroup parentThread;
                int totalThread = 0;
                for (parentThread = Thread.currentThread().getThreadGroup(); parentThread
                        .getParent() != null; parentThread = parentThread.getParent()) {
                    totalThread = parentThread.activeCount();
                }
                System.out.println("获得线程总数:" + totalThread);
                // 注意：这个定时任务若要使用spring中的功能，比如在这里借助spring往数据库写数据，这里会失败。
                // 程序会直接去调用spring中的线程并重启，这是因为spring本身有定时器。
            }
        };
        ScheduledExecutorService service = Executors.newSingleThreadScheduledExecutor();
        // 第二个参数为首次执行的延时时间，第三个参数为定时执行的间隔时间 单位秒
        service.scheduleAtFixedRate(runnable, 1, 10, TimeUnit.SECONDS);
    }

    @Override
    public void contextDestroyed(ServletContextEvent sce) {
    }
}