线程入门——捕获异常

示例：

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

/**
 * Created by Administrator on 2017/9/6.
 */

//任务
class ExceptionThread2 implements Runnable {
    @Override
    public void run() {
        Thread t = Thread.currentThread();
        System.out.println("run() by" + t);
        System.out.println(
                "eh = " + t.getUncaughtExceptionHandler()
        );
        throw new RuntimeException();
    }
}

//异常处理
class MyUncaughtExceptionHandler implements Thread.UncaughtExceptionHandler {
    @Override
    public void uncaughtException(Thread t, Throwable e) {
        System.out.print("caught" + e);
    }
}

//以线程方式启动任务
class HandlerThreadFactor implements ThreadFactory {
    public Thread newThread(Runnable r) {
        System.out.println(this + " creating new Thread");
        Thread t = new Thread(r);
        System.out.println("created " + t);
        t.setUncaughtExceptionHandler(new MyUncaughtExceptionHandler());
        System.out.println(
                "eh = " + t.getUncaughtExceptionHandler()
        );
        return t;

    }
}


public class CaptureUncaughtException {
    public static void main(String[] args){
        ExecutorService exec = Executors.newCachedThreadPool(new HandlerThreadFactor());
        exec.execute(new ExceptionThread2());
    }

}

输出结果：

因为线程的本质特性，使得你不能捕获从线程中逃逸的异常。一旦异常逃出任务的run()方法以外，它就会向外传播到控制台，除非你采起特殊的步骤捕获这些错误的异常。能够用Executor来解决这个问题。

Thread.UncaughtException-Handler是Java SE中的新接口，它容许你在每一个Thread对象上都附着一个异常处理器，Thread.UncaughtExceptionHandler.uncaughtException()会在线程因未捕获的异常而临近死亡时被调用，为了使用它，创新了一个新类型的ThreadFactory,它将在每一个新建立的Thread对象上附着一个Thread.UncaughtExceptionHandler。将这个工厂传递给Executors建立新的ExecutorService的方法。