JAVA线程异常终止
static void setDefaultUncaughtExceptionHandler(Thread.UncaughtExceptionHandler eh) 
设置当线程由于未捕获的异常突然终止而调用的默认处理程序,并且没有为该线程定义其他处理程序。  

我们开发工程中经常使用到线程,在线程使用上,我们可能会有这样的场景:

  1. 伴随这一个业务产生一个比较耗时的任务,而这个业务返回并不需要等待该任务。那我们往往会启动一个线程去完成这个异步任务。

  2. 我们需要一个定时任务比如:定时清除数据,我们会起一个定时执行线程去做该任务。
      

上述问题比较简单,new一个线程然后去做这件事。但是我们常常忽略一个问题,线程异常了怎么办?
比如耗时任务我们只完成了一半,我们就异常结束了(这里不考虑事务一致性,我们只考虑一定要将任务完成)。又比如在清数据的时候,数据库发生断连。这时候我们会发现线程死掉了,任务终止了,我们需要重启整个项目把该定时任务起起来。

场景一解决思路:

package cn.merryyou.thread;

/**
 * Created by 11 on 2017/7/5.
 */
public class Plan {

    private SimpleTask task = new SimpleTask();
    public static void main(String[] args) {
        Plan plan = new Plan();
        plan.start();
    }

    public void start(){
        Thread thread = new Thread(task);
        thread.setUncaughtExceptionHandler((t, e) -> {
            System.out.println(e.getMessage());
            start();
        });
        thread.start();
    }

    static class SimpleTask implements Runnable{

        private int task = 10;

        @Override
        public void run() {
            String threadName = Thread.currentThread().getName();
            System.out.println(threadName+"--"+"启动");
            while(task>0){
                try {
                    Thread.sleep(100);
                }catch (InterruptedException e){
                    e.printStackTrace();
                }
                if(System.currentTimeMillis()%3==0){
                    throw new RuntimeException("模拟异常");
                }
                System.out.println(threadName+"--"+"执行task"+task);
                task--;
            }
            System.out.println(threadName+"--"+"正常终止");
        }
    }
}

输出:

Thread-0--启动
Thread-0--执行task10
Thread-0--执行task9
Thread-0--执行task8
模拟异常
Thread-1--启动
Thread-1--执行task7
模拟异常
Thread-2--启动
模拟异常
Thread-3--启动
Thread-3--执行task6
模拟异常
Thread-4--启动
Thread-4--执行task5
模拟异常
Thread-5--启动
Thread-5--执行task4
模拟异常
Thread-6--启动
Thread-6--执行task3
模拟异常
Thread-7--启动
Thread-7--执行task2
Thread-7--执行task1
Thread-7--正常终止

线程池实现的方式:

package cn.merryyou.thread;

import sun.java2d.pipe.SpanShapeRenderer;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.ThreadFactory;

/**
 * Created by 11 on 2017/7/5.
 */
public class Plan2 {
    private Plan.SimpleTask task = new Plan.SimpleTask();
    private MyFactory factory = new MyFactory(task);
    public static void main(String[] args) {
        Plan2 plan2 = new Plan2();
        ExecutorService pool = Executors.newSingleThreadExecutor(plan2.factory);
        pool.execute(plan2.task);
        pool.shutdown();
    }

    class MyFactory implements ThreadFactory {

        private Plan.SimpleTask task;

        public MyFactory(Plan.SimpleTask task) {
            super();
            this.task = task;
        }

        @Override
        public Thread newThread(Runnable r) {
            Thread thread = new Thread(r);
            thread.setUncaughtExceptionHandler((t, e) -> {
                ExecutorService pool = Executors.newSingleThreadExecutor(new MyFactory(task));
                pool.execute(task);
                pool.shutdown();
            });
            return thread;
        }
    }
}

输出:

Thread-0--启动
Thread-0--执行task10
Thread-1--启动
Thread-1--执行task9
Thread-1--执行task8
Thread-1--执行task7
Thread-2--启动
Thread-2--执行task6
Thread-3--启动
Thread-3--执行task5
Thread-3--执行task4
Thread-3--执行task3
Thread-3--执行task2
Thread-3--执行task1
Thread-3--正常终止

定时任务ScheduledExecutorService 实现方式:

package cn.merryyou.thread;

import java.util.concurrent.*;

/**
 * Created by 11 on 2017/7/5.
 */
public class Plan3 {
    private SimpleTask task = new SimpleTask();
    public static void main(String[] args) {
        Plan3 plan = new Plan3();
        start(plan.task);
    }

    public static void start(SimpleTask task){
        ScheduledExecutorService pool = Executors.newSingleThreadScheduledExecutor();
        ScheduledFuture<?> future = pool.scheduleAtFixedRate(task, 0, 1000, TimeUnit.MILLISECONDS);
        try {
            future.get();
        }catch (InterruptedException | ExecutionException e){
            System.out.println(e.getMessage());
            start(task);
        }finally {
            pool.shutdown();
        }

    }

    class SimpleTask implements Runnable{
        private volatile int count = 0;

        @Override
        public void run() {
            String threadName = Thread.currentThread().getName();
            System.out.println(threadName+"--启动");
            try{
                Thread.sleep(100);
            }catch (InterruptedException e){
                e.printStackTrace();
            }
            if(System.currentTimeMillis()%3==0){
                throw new RuntimeException("模拟异常");
            }
            System.out.println(threadName+"--执行task"+count);
            count++;
            System.out.println(threadName+"--正常终止");
        }
    }
}

输出:

pool-1-thread-1--启动
pool-1-thread-1--执行task0
pool-1-thread-1--正常终止
pool-1-thread-1--启动
java.lang.RuntimeException: 模拟异常
pool-2-thread-1--启动
java.lang.RuntimeException: 模拟异常
pool-3-thread-1--启动
java.lang.RuntimeException: 模拟异常
pool-4-thread-1--启动
java.lang.RuntimeException: 模拟异常
pool-5-thread-1--启动
java.lang.RuntimeException: 模拟异常
pool-6-thread-1--启动
java.lang.RuntimeException: 模拟异常
pool-7-thread-1--启动
java.lang.RuntimeException: 模拟异常
pool-8-thread-1--启动
pool-8-thread-1--执行task1
pool-8-thread-1--正常终止
pool-8-thread-1--启动
pool-8-thread-1--执行task2
pool-8-thread-1--正常终止
pool-8-thread-1--启动
......

参考链接:http://www.cnblogs.com/yuhuihong19941210/p/5547501.html

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