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  /*
   * Copyright (C) 2006 The Guava Authors
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   * http://www.apache.org/licenses/LICENSE-2.0
   *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
 
 package com.google.common.util.concurrent;
 
 import static com.google.common.base.Preconditions.checkArgument;
 import static com.google.common.base.Preconditions.checkNotNull;
 
 
 import java.util.Set;
A TimeLimiter that runs method calls in the background using an java.util.concurrent.ExecutorService. If the time limit expires for a given method call, the thread running the call will be interrupted.

Author(s):
Kevin Bourrillion
Since:
1.0
 
 public final class SimpleTimeLimiter implements TimeLimiter {
 
   private final ExecutorService executor;

  
Constructs a TimeLimiter instance using the given executor service to execute proxied method calls.

Warning: using a bounded executor may be counterproductive! If the thread pool fills up, any time callers spend waiting for a thread may count toward their time limit, and in this case the call may even time out before the target method is ever invoked.

Parameters:
executor the ExecutorService that will execute the method calls on the target objects; for example, a java.util.concurrent.Executors.newCachedThreadPool().
 
   public SimpleTimeLimiter(ExecutorService executor) {
     this. = checkNotNull(executor);
   }

  
Constructs a TimeLimiter instance using a java.util.concurrent.Executors.newCachedThreadPool() to execute proxied method calls.

Warning: using a bounded executor may be counterproductive! If the thread pool fills up, any time callers spend waiting for a thread may count toward their time limit, and in this case the call may even time out before the target method is ever invoked.

 
   public SimpleTimeLimiter() {
     this(Executors.newCachedThreadPool());
   }
 
   @Override
   public <T> T newProxy(final T targetClass<T> interfaceType,
       final long timeoutDurationfinal TimeUnit timeoutUnit) {
     checkNotNull(target);
     checkNotNull(interfaceType);
     checkNotNull(timeoutUnit);
     checkArgument(timeoutDuration > 0, "bad timeout: " + timeoutDuration);
     checkArgument(interfaceType.isInterface(),
         "interfaceType must be an interface type");
 
     final Set<MethodinterruptibleMethods
         = findInterruptibleMethods(interfaceType);
 
     InvocationHandler handler = new InvocationHandler() {
       @Override
       public Object invoke(Object objfinal Method methodfinal Object[] args)
           throws Throwable {
        Callable<Objectcallable = new Callable<Object>() {
          @Override
          public Object call() throws Exception {
            try {
              return method.invoke(targetargs);
            } catch (InvocationTargetException e) {
              throwCause(efalse);
              throw new AssertionError("can't get here");
            }
          }
        };
        return callWithTimeout(callabletimeoutDurationtimeoutUnit,
            interruptibleMethods.contains(method));
      }
    };
    return newProxy(interfaceTypehandler);
  }
  // TODO: should this actually throw only ExecutionException?
  public <T> T callWithTimeout(Callable<T> callablelong timeoutDuration,
      TimeUnit timeoutUnitboolean amInterruptiblethrows Exception {
    checkNotNull(callable);
    checkNotNull(timeoutUnit);
    checkArgument(timeoutDuration > 0, "timeout must be positive: %s",
        timeoutDuration);
    Future<T> future = .submit(callable);
    try {
      if (amInterruptible) {
        try {
          return future.get(timeoutDurationtimeoutUnit);
        } catch (InterruptedException e) {
          future.cancel(true);
          throw e;
        }
      } else {
        return Uninterruptibles.getUninterruptibly(future
            timeoutDurationtimeoutUnit);
      }
    } catch (ExecutionException e) {
      throw throwCause(etrue);
    } catch (TimeoutException e) {
      future.cancel(true);
      throw new UncheckedTimeoutException(e);
    }
  }
  private static Exception throwCause(Exception eboolean combineStackTraces)
      throws Exception {
    Throwable cause = e.getCause();
    if (cause == null) {
      throw e;
    }
    if (combineStackTraces) {
      StackTraceElement[] combined = ObjectArrays.concat(cause.getStackTrace(),
          e.getStackTrace(), StackTraceElement.class);
      cause.setStackTrace(combined);
    }
    if (cause instanceof Exception) {
      throw (Exceptioncause;
    }
    if (cause instanceof Error) {
      throw (Errorcause;
    }
    // The cause is a weird kind of Throwable, so throw the outer exception.
    throw e;
  }
  private static Set<MethodfindInterruptibleMethods(Class<?> interfaceType) {
    Set<Methodset = Sets.newHashSet();
    for (Method m : interfaceType.getMethods()) {
      if (declaresInterruptedEx(m)) {
        set.add(m);
      }
    }
    return set;
  }
  private static boolean declaresInterruptedEx(Method method) {
    for (Class<?> exType : method.getExceptionTypes()) {
      // debate: == or isAssignableFrom?
      if (exType == InterruptedException.class) {
        return true;
      }
    }
    return false;
  }
  // TODO: replace with version in common.reflect if and when it's open-sourced
  private static <T> T newProxy(
      Class<T> interfaceTypeInvocationHandler handler) {
    Object object = Proxy.newProxyInstance(interfaceType.getClassLoader(),
        new Class<?>[] { interfaceType }, handler);
    return interfaceType.cast(object);
  }
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