3. 線程池——ThreadPoolExecutor增強之得到線程的異常信息

若直接使用ThreadPoolExecutor講沒法獲得線程的異常信息，因此在這裏對ThreadPoolExecutor進行增強

---

自定義任務類

public static class MyTask implements Runnable{
	private int a;
	private int b;
	public MyTask(int a, int b){this.a = a; this.b = b;}
	@Override
	public void run() {
		System.out.println(a/b);
	}
}

自定義線程池

public static 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 task) {
		super.execute(wrap(task, clientTrace(), Thread.currentThread().getName()));
	}

	@Override
	public Future<?> submit(Runnable task) {
		return super.submit(wrap(task, clientTrace(), Thread.currentThread().getName()));
	}

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

	//經過一個新的Runnable的run方法來包裝task的run方法，
	// 兩個參數都使用final，這樣新的Runnable在使用task和clientStack就不會出錯了。
	private Runnable wrap(final Runnable task, final Exception clientStack, String clientThreadName){
		return () -> {
			try{
				task.run(); //後續會在這裏執行線程
			} catch (Exception e){
				clientStack.printStackTrace();  //若線程發生錯誤會在這裏打印異常信息
				throw e;
			}
		};
	}
}

---

測試ThreadPoolExecutor

public static void main(String[] args){
	ThreadPoolExecutor pe =
            new ThreadPoolExecutor(0, 10, 30L, TimeUnit.SECONDS, new LinkedBlockingDeque<>());
//			  new TraceThreadPoolExecutor(0, 10,30L, TimeUnit.SECONDS, new LinkedBlockingDeque<>());


	for(int i=0 ; i<5 ; i++){
//            pe.submit(new MyTask(100, i));
		pe.execute(new MyTask(100, i));

		/* ThreadPoolExecutor.submit，不會打印任何錯誤信息
		 * ThreadPoolExecutor.execute，打印線程異常信息
		 * TraceThreadPoolExecutor.submit，只打印部分信息（哪裏建立了異常線程）
		 * TraceThreadPoolExecutor.execute，打印了所有異常信息(包括建立異常線程的位置，已經哪裏發生了異常)
		 */
	}
	pe.shutdown();
}

console

Exception in thread "pool-1-thread-1" 100
50
33
25
java.lang.ArithmeticException: / by zero
	at concurrent.C03_TraceThreadPoolExecutor$MyTask.run(C03_TraceThreadPoolExecutor.java:16)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)

雖然控制檯提示咱們有錯誤，可是咱們並不知道錯誤發生在什麼地方，這不利於咱們定位錯誤。

---

測試TraceThreadPoolExecutor

public static void main(String[] args){
	ThreadPoolExecutor pe =
			new TraceThreadPoolExecutor(0, 10,30L, TimeUnit.SECONDS, new LinkedBlockingDeque<>());


	for(int i=0 ; i<5 ; i++){
//            pe.submit(new MyTask(100, i));
		pe.execute(new MyTask(100, i));

		/* ThreadPoolExecutor.submit，不會打印任何錯誤信息
		 * ThreadPoolExecutor.execute，打印線程異常信息
		 * TraceThreadPoolExecutor.submit，只打印部分信息（哪裏建立了異常線程）
		 * TraceThreadPoolExecutor.execute，打印了所有異常信息(包括建立異常線程的位置，已經哪裏發生了異常)
		 */
	}
	pe.shutdown();
}

console

java.lang.Exception: Client stack trace
	at concurrent.C03_TraceThreadPoolExecutor$TraceThreadPoolExecutor.clientTrace(C03_TraceThreadPoolExecutor.java:36)
	at concurrent.C03_TraceThreadPoolExecutor$TraceThreadPoolExecutor.execute(C03_TraceThreadPoolExecutor.java:27)
	at concurrent.C03_TraceThreadPoolExecutor.main(C03_TraceThreadPoolExecutor.java:63)
Exception in thread "pool-1-thread-1" java.lang.ArithmeticException: / by zero
	at concurrent.C03_TraceThreadPoolExecutor$MyTask.run(C03_TraceThreadPoolExecutor.java:16)
100
50
33
25
	at concurrent.C03_TraceThreadPoolExecutor$TraceThreadPoolExecutor.lambda$0(C03_TraceThreadPoolExecutor.java:44)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)