我有一个同步执行路径，它需要在给定的时间范围内完成或超时。假设我有一个带有 main() 方法的类，在该类中我调用方法 A()，该方法又调用 B()，而该方法又调用相同或不同类的 C() .....所有同步而不使用外部资源，如数据库、Web 服务或文件系统（其中每个都可以使用 TxManager 或相应的超时 API 独立超时）。所以它更像是 CPU 或内存密集型计算。如何在 Java 中为其超时编写代码？
我查看了 TimerTask，但更多的是使流异步和调度任务。还有其他建议吗？
【问题讨论】：
ExecutorService 和 Callables 可能是!!!
标签： java timeout synchronous
您可以运行一个并行线程，该线程将等待指定的超时并中断当前线程，然后运行A()。但是a、b、c必须是可中断的，即定期检查当前线程的中断标志并抛出InterruptedException，否则将不起作用
final Thread current = Thread.currentThread();
Thread timer = new Thread() {
public void run() {
try {
Thread.sleep(5000);
current.interrupt();
} catch (InterruptedException e) {
// timer stopped
}
};
};
try {
A(); // this throws InterruptedException if interrupted by timer
timer.interrupt(); // no timeout lets stop the timer
} catch (InterruptedException e) {
// timeout
}
【讨论】：
您应该使用ExecutorService 来做到这一点
ExecutorService executor = Executors.newSingleThreadExecutor();
Future<String> future = executor.submit(new Callable() {
public String call() throws Exception {
//do operations you want
return "OK";
}
});
try {
System.out.println(future.get(2, TimeUnit.SECONDS)); //timeout is in 2 seconds
} catch (TimeoutException e) {
System.err.println("Timeout");
}
executor.shutdownNow();
【讨论】：
另见post 该方法是让您的应用程序在其逻辑中处理超时。为此，您可以定义一些计时器类和特殊检查方法，例如：
public class TimeoutApp {
MyTimer timer;
Thread timerThread;
public static void main(String... args) {
new TimeoutApp().execute();
}
private void execute() {
try {
startTimer(1000);
action1();
checkTimeout();
action2();
checkTimeout();
action3();
stopTimer();
} catch (MyTimeoutException e) {
System.out.println("Interrupted on timeout!");
// ...clearing code if needed
System.exit(1);
} catch (InterruptedException e) {
System.out.println("Interrupted by exception!");
// ...clearing code if needed
e.printStackTrace();
System.exit(1);
}
}
private void action1() throws InterruptedException {
Thread.sleep(600);
System.out.println("action 1");
}
private void action2() throws InterruptedException {
Thread.sleep(500);
System.out.println("action 2");
}
private void action3() {
System.out.println("action 3");
}
private void checkTimeout() throws MyTimeoutException {
if (timer.isTimeoutReached()) {
throw new MyTimeoutException();
}
}
private void startTimer(long timeout) {
timer = new MyTimer(timeout);
timerThread = new Thread(timer);
timerThread.start();
}
private void stopTimer() {
timerThread.interrupt();
}
private class MyTimer implements Runnable {
private long timeout;
private boolean timeoutReached = false;
public MyTimer(long timeout) {
this.timeout = timeout;
}
public void run() {
long time = System.currentTimeMillis();
while (!timeoutReached && !Thread.interrupted()) {
if ((System.currentTimeMillis() - time) > timeout) {
timeoutReached = true;
}
}
}
public boolean isTimeoutReached() {
return timeoutReached;
}
}
private class MyTimeoutException extends Exception {
}
}
【讨论】：
您无法使用超时进行同步调用，但您可以使用第二个线程来模拟它。这是一个例子：
package com.ardevco.example;
import java.util.Random;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
class ExceptionThrower {
public static <R> R throwUnchecked(Throwable t) {
return ExceptionThrower.<RuntimeException, R> trhow0(t);
}
@SuppressWarnings("unchecked")
private static <E extends Throwable, R> R trhow0(Throwable t) throws E {
throw (E) t;
}
}
class TestApplicationException1 extends Exception {
private static final long serialVersionUID = 1L;
public TestApplicationException1(String string) {
super(string);
}
};
class TestApplicationException2 extends Exception {
private static final long serialVersionUID = 1L;
public TestApplicationException2(String string) {
super(string);
}
};
class TestApplicationTimeoutException extends Exception {
private static final long serialVersionUID = 1L;
public TestApplicationTimeoutException(String string) {
super(string);
};
}
public class SynchronousTimeoutTester {
public static final long SYNC_METHOD_TIMEOUT_IN_MILLISECONDS = 2000L;
private final ExecutorService executorService = Executors.newSingleThreadExecutor();
public static void main(String[] args) {
SynchronousTimeoutTester tester = new SynchronousTimeoutTester();
/* call the method asynchronously 10 times */
for (int i = 0; i < 10; i++) {
try {
System.out.println("Result sync call: " + tester.getAsynchTest());
}
catch (TestApplicationException1 e) {
System.out.println("catched as TestApplicationException1: " + e);
}
catch (TestApplicationException2 e) {
System.out.println("catched as TestApplicationException2: " + e);
}
catch (TestApplicationTimeoutException e) {
System.out.println("catched as TestApplicationTimeoutException: " + e);
}
catch (InterruptedException e) {
System.out.println("catched as InterruptedException: " + e);
}
catch (Exception e) {
System.out.println("catched as Exception: " + e);
}
}
tester.shutdown();
}
private void shutdown() {
executorService.shutdown();
try {
executorService.awaitTermination(Long.MAX_VALUE, TimeUnit.NANOSECONDS);
}
catch (InterruptedException e) {
System.out.println("Error stopping threadpool:" + e);
}
}
private Integer testAsynch() throws TestApplicationException1, TestApplicationException2, InterruptedException {
Random random = new Random();
switch (random.nextInt(10)) {
case 0:
return 0;
case 1:
throw new TestApplicationException1("thrown TestApplicationException1");
case 2:
throw new TestApplicationException2("thrown TestApplicationException2");
case 3:
Thread.sleep(10000L);
return -1;
case 4:
throw new RuntimeException("thrown Exception");
default:
return random.nextInt(10);
}
}
private Integer getAsynchTest() throws TestApplicationException1, TestApplicationException2, Exception {
Integer dummy = null;
Future<Integer> testAsynchF = executorService.submit(
new Callable<Integer>() {
public Integer call() throws Exception {
return testAsynch();
}
});
try {
dummy = testAsynchF.get(SynchronousTimeoutTester.SYNC_METHOD_TIMEOUT_IN_MILLISECONDS, TimeUnit.MILLISECONDS);
}
catch (ExecutionException e1) {
System.out.println("in getAsynchTest: ExecutionException: " + e1);
ExceptionThrower.throwUnchecked(e1.getCause());
}
catch (TimeoutException e1) {
System.out.println("in getAsynchTest: TimeoutException: " + e1);
throw new TestApplicationTimeoutException("TimeoutException" + e1);
}
catch (InterruptedException e1) {
System.out.println("in getAsynchTest: InterruptedException: " + e1);
throw new Exception(e1);
}
return dummy;
}
}
【讨论】：