Question

我有一个Controller类和一个Monitor工作线程。控制器线程看起来像这样

public class ControllerA {
    public void ControllerA(){
        try{
            doWork();
        }
        catch(OhNoException e){
        //catch exception
        }

    public void doWork() throws OhNoException{

      new Thread(new Runnable(){
        public void run(){
        //Needs to monitor resources of ControllerA, 
        //if things go wrong, it needs to throw OhNoException for its parent
        }
        }).start();

      //do work here

    }
}

这种设置是否可行？如何将异常抛出到线程的外部？

Answer 1

如何将异常抛出到线程外部？

你可以通过几种方式做到这一点。您可以在主题上设置UncaughtExceptionHandler，也可以使用ExecutorService.submit(Callable)并使用从Future.get()获得的例外。

最简单的方法是使用ExecutorService：

ExecutorService threadPool = Executors.newSingleThreadScheduledExecutor();
Future<Void> future = threadPool.submit(new Callable<Void>() {
      public Void call() throws Exception {
         // can throw OhNoException here
         return null;
     }
});
// you need to shut down the pool after submitting the last task
threadPool.shutdown();
// this can throw ExecutionException
try {
   // this waits for your background task to finish, it throws if the task threw
   future.get();
} catch (ExecutionException e) {
    // this is the exception thrown by the call() which could be a OhNoException
    Throwable cause = e.getCause();
     if (cause instanceof OhNoException) {
        throw (OhNoException)cause;
     } else if (cause instanceof RuntimeException) {
        throw (RuntimeException)cause;
     }
}

如果您想使用UncaughtExceptionHandler，那么您可以执行以下操作：

 Thread thread = new Thread(...);
 final AtomicReference throwableReference = new AtomicReference<Throwable>();
 thread.setUncaughtExceptionHandler(new UncaughtExceptionHandler() {
     public void uncaughtException(Thread t, Throwable e) {
         throwableReference.set(e);
     }
 });
 thread.start();
 thread.join();
 Throwable throwable = throwableReference.get();
 if (throwable != null) {
     if (throwable instanceof OhNoException) {
        throw (OhNoException)throwable;
     } else if (throwable instanceof RuntimeException) {
        throw (RuntimeException)throwable;
     }
 }

Answer 2

Runnable接口不能抛出已检查的异常或返回值。在Callable接口中，您可以调用任何返回值或抛出异常的worker方法。监视器的主要任务是

使用可调用实例声明和初始化未来。
一个getResult（）方法，它可以有一个return future.get();语句，并且应该在其throws子句中声明任何已检查的异常，以便它由调用代码处理。这样我们就不必返回null。

嵌套线程可以为父线程抛出异常吗？

2 个答案: