从Java ExecutorService捕获线程异常
我正在研究一个用于并行计算的软件开发框架。我需要一个健壮的机制来报告线程异常。在开发过程中,了解异常来自何处具有很高的价值,因此我希望在过度报告方面犯错误。我还希望能够在线程中处理Junit4测试。下面的方法是合理的还是有更好的方法从Java ExecutorService捕获线程异常,java,multithreading,exception,Java,Multithreading,Exception,我正在研究一个用于并行计算的软件开发框架。我需要一个健壮的机制来报告线程异常。在开发过程中,了解异常来自何处具有很高的价值,因此我希望在过度报告方面犯错误。我还希望能够在线程中处理Junit4测试。下面的方法是合理的还是有更好的方法 import java.util.concurrent.Callable; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
public class TestThreadFailure {
public static void main(String[] args) {
int size = 1;
ExecutorService exec = Executors.newFixedThreadPool(size);
ThreadFailTask worker = new ThreadFailTask();
Future<Integer> result = exec.submit(worker);
try {
Integer value = result.get();
System.out.println("Result: " + value);
} catch (Throwable t) {
System.out.println("Caught failure: " + t.toString());
exec.shutdownNow();
System.out.println("Stack Trace:");
t.printStackTrace();
return;
}
throw new RuntimeException("Did not catch failure !!");
}
public static class ThreadFailTask implements Callable<Integer> {
@Override
public Integer call() {
int nbuf = 65536;
double[][] buf = new double[nbuf][nbuf];
return new Integer((int) buf[0][0]);
}
}
}
import java.util.concurrent.Callable;
导入java.util.concurrent.ExecutorService;
导入java.util.concurrent.Executors;
导入java.util.concurrent.Future;
公共类TestThreadFailure{
公共静态void main(字符串[]args){
int size=1;
ExecutorService exec=Executors.newFixedThreadPool(大小);
ThreadFailTask worker=新的ThreadFailTask();
未来结果=执行提交(工人);
试一试{
整数值=result.get();
System.out.println(“结果:+值);
}捕获(可丢弃的t){
System.out.println(“捕获的故障:+t.toString());
exec.shutdownNow();
System.out.println(“堆栈跟踪:”);
t、 printStackTrace();
返回;
}
抛出新的RuntimeException(“未捕获失败!!”);
}
公共静态类ThreadFailTask实现可调用{
@凌驾
公共整数调用(){
int-nbuf=65536;
双精度[][]buf=新双精度[nbuf][nbuf];
返回新整数((int)buf[0][0]);
}
}
}
请考虑呼叫,而不是在网络上。使用execute()
调用的将在失败时调用
只需创建一个在所有线程上安装线程的.UncaughtExceptionHandler
,然后使用ExecutorService
上的execute()
调用您的工作,而不是submit()
看看这一点。正如本线程中所解释的,只有在实现可运行和不可调用的情况下,使用execute才有效,因为execute无法返回未来
我认为在您的场景中,您应该构建future对象,以便它也可以容纳异常内容。因此,如果出现异常,您将构建错误消息对象。我认为在使用submit()
时,没有标准的“钩子”来访问这些异常。但是,如果您需要支持submit()
(这听起来很合理,因为您使用了Callable
),那么您可以始终包装Callable和runnable:
ExecutorService executor = new ThreadPoolExecutor(1, 10, 60, TimeUnit.SECONDS, new LinkedBlockingDeque<Runnable>()) {
@Override
public <T> Future<T> submit(final Callable<T> task) {
Callable<T> wrappedTask = new Callable<T>() {
@Override
public T call() throws Exception {
try {
return task.call();
}
catch (Exception e) {
System.out.println("Oh boy, something broke!");
e.printStackTrace();
throw e;
}
}
};
return super.submit(wrappedTask);
}
};
ExecutorService executor=new ThreadPoolExecutor(1,10,60,TimeUnit.SECONDS,new LinkedBlockingDeque()){
@凌驾
公共未来提交(最终可调用任务){
Callable wrappedTask=新的Callable(){
@凌驾
public T call()引发异常{
试一试{
返回task.call();
}
捕获(例外e){
System.out.println(“哦,天哪,有东西坏了!”);
e、 printStackTrace();
投掷e;
}
}
};
返回super.submit(wrappedTask);
}
};
当然,只有当您首先构建ExecutorService
时,这种方法才有效。此外,请记住覆盖所有三个submit()
变体。我最初的问题是如何使用Java ExecutorService实现“健壮”的线程异常处理。感谢Angelo和Greg为ExecutorService.submit()和Future.get()异常处理提供了指导。我修改后的代码片段如下所示。我在这里学到的关键点是Future.get()捕获所有异常。如果线程被中断或取消,您将获得相应的异常,否则,该异常将被包装并作为ExecutionException重新抛出
import java.util.concurrent.Callable;
import java.util.concurrent.CancellationException;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
public class TestThreadFailure {
public static void main(String[] args) {
int size = 1;
ExecutorService exec = Executors.newFixedThreadPool(size);
ThreadFailTask worker = new ThreadFailTask();
Future result = exec.submit(worker);
try {
Integer value = result.get();
System.out.println("Result: " + value);
} catch (ExecutionException ex) {
System.out.println("Caught failure: " + ex.toString());
exec.shutdownNow();
return;
} catch (InterruptedException iex) {
System.out.println("Thread interrupted: " + iex.toString());
} catch (CancellationException cex) {
System.out.println("Thread cancelled: " + cex.toString());
}
exec.shutdownNow();
throw new RuntimeException("Did not catch failure !!");
}
public static class ThreadFailTask implements Callable {
@Override
public Integer call() {
int nbuf = 65536;
double[][] buf = new double[nbuf][nbuf];
return new Integer((int) buf[0][0]);
}
}
}
导入java.util.concurrent.Callable;
导入java.util.concurrent.CancellationException;
导入java.util.concurrent.ExecutionException;
导入java.util.concurrent.ExecutorService;
导入java.util.concurrent.Executors;
导入java.util.concurrent.Future;
公共类TestThreadFailure{
公共静态void main(字符串[]args){
int size=1;
ExecutorService exec=Executors.newFixedThreadPool(大小);
ThreadFailTask worker=新的ThreadFailTask();
未来结果=执行提交(工人);
试一试{
整数值=result.get();
System.out.println(“结果:+值);
}捕获(ExecutionException ex){
System.out.println(“捕获故障:+ex.toString());
exec.shutdownNow();
返回;
}捕获(中断异常iex){
System.out.println(“线程中断:+iex.toString());
}捕获(取消异常cex){
System.out.println(“线程取消:+cex.toString());
}
exec.shutdownNow();
抛出新的RuntimeException(“未捕获失败!!”);
}
公共静态类ThreadFailTask实现可调用{
@凌驾
公共整数调用(){
int-nbuf=65536;
双精度[][]buf=新双精度[nbuf][nbuf];
返回新整数((int)buf[0][0]);
}
}
}
要在ExecutorService中处理异常,您必须利用可调用和未来
Callable类似于Runnable,两者都是函数接口,但Runnable的run()不会引发异常,返回类型为void,其中Callable的ascall()返回泛型并引发异常
Java-8方式:
ExecuterService executor = null;
Future<Integer> future = null;
Callable<Integer> yourTask = () -> {
//your implementation here();
//your implementation here();
};
try
{
executor = Executors.newCachedThreadPool();
future = executor.submit(yourTask );
Integer result = future.get();
System.out.println(result);
}
catch (ExecutionException | TimeoutException | InterruptedException e)
{
// TODO: handle exception
}
finally
{
executer.shutdown();
}
ExecuterService executor=null;
Future=null;
可调用的yourTask=()->{
//您在这里的实现();
//您在这里的实现();
};
尝试
{
executor=Executors.newCachedThreadPool();
future=执行者。提交(您的任务);
整数结果=future.get();
系统输出打印项次(结果);
}
捕获(ExecutionException | TimeoutException | InterruptedException e)
{
//TODO:处理异常
}
fi
List<Runnable> tasks = new LinkedList<>();
for (int i = 0; i < numThreads; ++i) {
Runnable task = new Runnable() {
@Override
public void run() {
throw new RuntimeException();
}
};
tasks.add(task);
}
Optional<Throwable> opEmpty = Optional.empty();
/*
* Use AtomicReference as a means of capturing the first thrown exception, since a
* spawned thread can't "throw" an exception to the parent thread.
*/
final AtomicReference<Optional<Throwable>> firstThrownException =
new AtomicReference<>(opEmpty);
/*
* Use new ThreadPoolExecutor instead of Executors.newFixedThreadPool() so
* that I can override afterExecute() for the purposes of throwing an
* exception from the test thread if a child thread fails.
*/
ExecutorService execSvc = new ThreadPoolExecutor(numThreads, numThreads,
0L, TimeUnit.MILLISECONDS, new LinkedBlockingQueue<Runnable>()) {
@Override
public void afterExecute(Runnable task, Throwable failureCause) {
if(failureCause == null) {
// The Runnable completed successfully.
return;
}
// only sets the first exception because it will only be empty on the first call.
firstThrownException.compareAndSet(Optional.<Throwable>empty(), Optional.of(failureCause));
}
};
for (Runnable task : tasks) {
execSvc.execute(task);
}
execSvc.shutdown();
execSvc.awaitTermination(1, TimeUnit.HOURS);
assertEquals(firstThrownException.get(), Optional.empty());