static void setDefaultUncaughtExceptionHandler(Thread.UncaughtExceptionHandler eh)
設(shè)置當(dāng)線程由于未捕獲的異常突然終止而調(diào)用的默認(rèn)處理程序幽告，并且沒有為該線程定義其他處理程序。
我們開發(fā)工程中經(jīng)常使用到線程裆甩，在線程使用上冗锁，我們可能會有這樣的場景：
- 伴隨這一個業(yè)務(wù)產(chǎn)生一個比較耗時的任務(wù)，而這個業(yè)務(wù)返回并不需要等待該任務(wù)嗤栓。那我們往往會啟動一個線程去完成這個異步任務(wù)冻河。
- 我們需要一個定時任務(wù)比如：定時清除數(shù)據(jù)，我們會起一個定時執(zhí)行線程去做該任務(wù)茉帅。
上述問題比較簡單芋绸，new一個線程然后去做這件事。但是我們常常忽略一個問題担敌，線程異常了怎么辦？
比如耗時任務(wù)我們只完成了一半廷蓉，我們就異常結(jié)束了（這里不考慮事務(wù)一致性全封，我們只考慮一定要將任務(wù)完成）。又比如在清數(shù)據(jù)的時候桃犬，數(shù)據(jù)庫發(fā)生斷連刹悴。這時候我們會發(fā)現(xiàn)線程死掉了，任務(wù)終止了攒暇，我們需要重啟整個項目把該定時任務(wù)起起來土匀。
場景一解決思路：
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+"--"+"啟動");
while(task>0){
try {
Thread.sleep(100);
}catch (InterruptedException e){
e.printStackTrace();
}
if(System.currentTimeMillis()%3==0){
throw new RuntimeException("模擬異常");
}
System.out.println(threadName+"--"+"執(zhí)行task"+task);
task--;
}
System.out.println(threadName+"--"+"正常終止");
}
}
}
輸出：
Thread-0--啟動
Thread-0--執(zhí)行task10
Thread-0--執(zhí)行task9
Thread-0--執(zhí)行task8
模擬異常
Thread-1--啟動
Thread-1--執(zhí)行task7
模擬異常
Thread-2--啟動
模擬異常
Thread-3--啟動
Thread-3--執(zhí)行task6
模擬異常
Thread-4--啟動
Thread-4--執(zhí)行task5
模擬異常
Thread-5--啟動
Thread-5--執(zhí)行task4
模擬異常
Thread-6--啟動
Thread-6--執(zhí)行task3
模擬異常
Thread-7--啟動
Thread-7--執(zhí)行task2
Thread-7--執(zhí)行task1
Thread-7--正常終止
線程池實現(xiàn)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;
}
}
}
輸出：
Thread-0--啟動
Thread-0--執(zhí)行task10
Thread-1--啟動
Thread-1--執(zhí)行task9
Thread-1--執(zhí)行task8
Thread-1--執(zhí)行task7
Thread-2--啟動
Thread-2--執(zhí)行task6
Thread-3--啟動
Thread-3--執(zhí)行task5
Thread-3--執(zhí)行task4
Thread-3--執(zhí)行task3
Thread-3--執(zhí)行task2
Thread-3--執(zhí)行task1
Thread-3--正常終止
定時任務(wù)ScheduledExecutorService 實現(xiàn)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+"--啟動");
try{
Thread.sleep(100);
}catch (InterruptedException e){
e.printStackTrace();
}
if(System.currentTimeMillis()%3==0){
throw new RuntimeException("模擬異常");
}
System.out.println(threadName+"--執(zhí)行task"+count);
count++;
System.out.println(threadName+"--正常終止");
}
}
}
輸出：
pool-1-thread-1--啟動
pool-1-thread-1--執(zhí)行task0
pool-1-thread-1--正常終止
pool-1-thread-1--啟動
java.lang.RuntimeException: 模擬異常
pool-2-thread-1--啟動
java.lang.RuntimeException: 模擬異常
pool-3-thread-1--啟動
java.lang.RuntimeException: 模擬異常
pool-4-thread-1--啟動
java.lang.RuntimeException: 模擬異常
pool-5-thread-1--啟動
java.lang.RuntimeException: 模擬異常
pool-6-thread-1--啟動
java.lang.RuntimeException: 模擬異常
pool-7-thread-1--啟動
java.lang.RuntimeException: 模擬異常
pool-8-thread-1--啟動
pool-8-thread-1--執(zhí)行task1
pool-8-thread-1--正常終止
pool-8-thread-1--啟動
pool-8-thread-1--執(zhí)行task2
pool-8-thread-1--正常終止
pool-8-thread-1--啟動
......
參考鏈接：http://www.cnblogs.com/yuhuihong19941210/p/5547501.html
