Java 線程池中如何捕獲堆棧異常

範例1：分母不能爲0的異常沒有拋出，程序竟然能成功地被執行

package com.myth;

import java.util.concurrent.SynchronousQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

public class DivTask implements Runnable {

    int a, b;

    public DivTask(int a, int b) {
        this.a = a;
        this.b = b;
    }

    @Override
    public void run() {
        double result = a / b;
        System.out.println("result = " + result);
    }

    public static void main(String[] args) {
        ThreadPoolExecutor pool = new ThreadPoolExecutor(0, Integer.MAX_VALUE, 0L, TimeUnit.SECONDS, new SynchronousQueue<Runnable>());
        for (int i = 0; i < 5; i++) {
            try{
            pool.submit(new DivTask(100, i));
            }catch(Exception e){
                e.printStackTrace();
            }
        }
    }
}

run:
result = 50.0
result = 33.0
result = 100.0
result = 25.0
BUILD SUCCESSFUL (total time: 0 seconds)

循環5次，提交5個任務，如果程序正確執行的話，同樣會打印輸出5個輸出結果，但是少了1個，

顯然以上代碼的錯誤，沒有被拋出來，不報告錯誤的多線程程序排錯那是非常傷腦筋的

範例2：換一種能捕獲異常提交任務的執行方式

package com.myth;

import java.util.concurrent.SynchronousQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

public class DivTask implements Runnable {

    int a, b;

    public DivTask(int a, int b) {
        this.a = a;
        this.b = b;
    }

    @Override
    public void run() {
        double result = a / b;
        System.out.println("result = " + result);
    }

    public static void main(String[] args) {
        ThreadPoolExecutor pool = new ThreadPoolExecutor(0, Integer.MAX_VALUE, 0L, TimeUnit.SECONDS, new SynchronousQueue<Runnable>());
        for (int i = 0; i < 5; i++) {
            try{
            pool.execute(new DivTask(100,i));
            }catch(Exception e){
                e.printStackTrace();
            }
        }
    }
}

run:
result = 100.0
Exception in thread "pool-1-thread-1" java.lang.ArithmeticException: / by zero
result = 50.0
result = 33.0
result = 25.0
	at com.myth.DivTask.run(DivTask.java:18)注意啦，錯誤顯示信息表示是第18行代碼double result = a / b拋出的
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)
BUILD SUCCESSFUL (total time: 2 seconds)

範例3：再換一種能捕獲異常提交任務的執行方式

 

package com.myth;

import java.util.concurrent.Future;
import java.util.concurrent.SynchronousQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

public class DivTask implements Runnable {

    int a, b;

    public DivTask(int a, int b) {
        this.a = a;
        this.b = b;
    }

    @Override
    public void run() {
        double result = a / b;
        System.out.println("result = " + result);
    }

    public static void main(String[] args) {
        ThreadPoolExecutor pool = new ThreadPoolExecutor(0, Integer.MAX_VALUE, 0L, TimeUnit.SECONDS, new SynchronousQueue<Runnable>());
        for (int i = 0; i < 5; i++) {
            try {
                Future data = pool.submit(new DivTask(100, i));
                data.get();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
}

run:
result = 100.0
java.util.concurrent.ExecutionException: java.lang.ArithmeticException: / by zero
result = 50.0
result = 33.0
result = 25.0
	at java.util.concurrent.FutureTask.report(FutureTask.java:122)
	at java.util.concurrent.FutureTask.get(FutureTask.java:192)
	at com.myth.DivTask.main(DivTask.java:28)
Caused by: java.lang.ArithmeticException: / by zero
	at com.myth.DivTask.run(DivTask.java:19) 注意啦，錯誤顯示信息表示是第19行代碼double result = a / b拋出的
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)
BUILD SUCCESSFUL (total time: 0 seconds)

範例4

package com.myth;

import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

public class DivTask implements Runnable {

    int a, b;
    String name;

    public DivTask(int a, int b,String name) {
        this.a = a;
        this.b = b;
        this.name = name;
    }
    
    public String getTaskName(){
        return name;
    }

    @Override
    public void run() {
        double result = a / b;
        System.out.println("result = " + result);
    }

    public static void main(String[] args) {
        ThreadPoolExecutor pool = new TraceThreadPoolExecutor(0, Integer.MAX_VALUE, 0L, TimeUnit.SECONDS, 
                new LinkedBlockingQueue<Runnable>());  // SynchronousQueue
        for (int i = 0; i < 5; i++) {
            try {
               // 錯誤堆棧中可以看到是在哪裏提交的任務
               pool.execute(new DivTask(100,i,"Task"+i));
            } catch (Exception e) {
              e.printStackTrace();
            }
        }
    }
}

package com.myth;

import java.util.concurrent.BlockingQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

public class TraceThreadPoolExecutor extends ThreadPoolExecutor {

    public TraceThreadPoolExecutor(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue) {
        super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue);
    }

    @Override
    public void execute(Runnable myTask) {  // 任務是在這裏提交的
        super.execute(wrap(myTask, clientTrace(), Thread.currentThread().getName()));
    }

    private Exception clientTrace() {
        return new Exception("Client stack trace");
    }

    private Runnable wrap(Runnable myTask, Exception clientStack, String clientThreadName) {
        return new Runnable() {
            @Override
            public void run() { // 而任務的具體提交位置在這裏
                try {
                    myTask.run();
                } catch (Exception e) {
                    clientStack.printStackTrace();
                    System.err.println("Client Thread Name：" + clientThreadName);
                    throw e;
                }
            }

        };
    }
}

run:
java.lang.Exception: Client stack trace
result = 100.0
result = 50.0
result = 33.0
result = 25.0
	at com.myth.TraceThreadPoolExecutor.clientTrace(TraceThreadPoolExecutor.java:19)
	at com.myth.TraceThreadPoolExecutor.execute(TraceThreadPoolExecutor.java:15)
	at com.myth.DivTask.main(DivTask.java:34)
Client Thread Name：main
Exception in thread "pool-1-thread-1" java.lang.ArithmeticException: / by zero
	at com.myth.DivTask.run(DivTask.java:24) 注意啦，錯誤顯示信息表示是第24行代碼double result = a / b拋出的
	at com.myth.TraceThreadPoolExecutor$1.run(TraceThreadPoolExecutor.java:27)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)
BUILD SUCCESSFUL (total time: 0 seconds)