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Java example source code file (TestThread.java)

This example Java source code file (TestThread.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

annotation, assertionfailederror, exception, methods, object, override, reflection, request, response, string, synchronousqueue, testthread, threaddeath, threading, threads, throwable, timeout_millis, timeoutexception

The TestThread.java Java example source code

/*
 * Copyright (C) 2010 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.checkNotNull;
import static junit.framework.Assert.assertEquals;
import static junit.framework.Assert.assertNotNull;
import static junit.framework.Assert.assertNull;
import static junit.framework.Assert.assertSame;

import com.google.common.testing.TearDown;

import junit.framework.AssertionFailedError;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.concurrent.SynchronousQueue;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;

import javax.annotation.Nullable;

/**
 * A helper for concurrency testing. One or more {@code TestThread} instances are instantiated
 * in a test with reference to the same "lock-like object", and then their interactions with that
 * object are choreographed via the various methods on this class.
 *
 * <p>A "lock-like object" is really any object that may be used for concurrency control. If the
 * {@link #callAndAssertBlocks} method is ever called in a test, the lock-like object must have a
 * method equivalent to {@link java.util.concurrent.locks.ReentrantLock#hasQueuedThread(Thread)}. If
 * the {@link #callAndAssertWaits} method is ever called in a test, the lock-like object must have a
 * method equivalent to {@link
 * java.util.concurrent.locks.ReentrantLock#hasWaiters(java.util.concurrent.locks.Condition)},
 * except that the method parameter must accept whatever condition-like object is passed into
 * {@code callAndAssertWaits} by the test.
 *
 * @param <L> the type of the lock-like object to be used
 * @author Justin T. Sampson
 */
public final class TestThread<L> extends Thread implements TearDown {

  private static final long DUE_DILIGENCE_MILLIS = 100;
  private static final long TIMEOUT_MILLIS = 5000;

  private final L lockLikeObject;

  private final SynchronousQueue<Request> requestQueue = new SynchronousQueue();
  private final SynchronousQueue<Response> responseQueue = new SynchronousQueue();

  private Throwable uncaughtThrowable = null;

  public TestThread(L lockLikeObject, String threadName) {
    super(threadName);
    this.lockLikeObject = checkNotNull(lockLikeObject);
    start();
  }

  // Thread.stop() is okay because all threads started by a test are dying at the end of the test,
  // so there is no object state put at risk by stopping the threads abruptly. In some cases a test
  // may put a thread into an uninterruptible operation intentionally, so there is no other way to
  // clean up these threads.
  @SuppressWarnings("deprecation")
  @Override public void tearDown() throws Exception {
    stop();
    join();

    if (uncaughtThrowable != null) {
      throw (AssertionFailedError) new AssertionFailedError("Uncaught throwable in " + getName())
          .initCause(uncaughtThrowable);
    }
  }

  /**
   * Causes this thread to call the named void method, and asserts that the call returns normally.
   */
  public void callAndAssertReturns(String methodName, Object... arguments) throws Exception {
    checkNotNull(methodName);
    checkNotNull(arguments);
    sendRequest(methodName, arguments);
    assertSame(null, getResponse(methodName).getResult());
  }

  /**
   * Causes this thread to call the named method, and asserts that the call returns the expected
   * boolean value.
   */
  public void callAndAssertReturns(boolean expected, String methodName, Object... arguments)
      throws Exception {
    checkNotNull(methodName);
    checkNotNull(arguments);
    sendRequest(methodName, arguments);
    assertEquals(expected, getResponse(methodName).getResult());
  }

  /**
   * Causes this thread to call the named method, and asserts that the call returns the expected
   * int value.
   */
  public void callAndAssertReturns(int expected, String methodName, Object... arguments)
      throws Exception {
    checkNotNull(methodName);
    checkNotNull(arguments);
    sendRequest(methodName, arguments);
    assertEquals(expected, getResponse(methodName).getResult());
  }

  /**
   * Causes this thread to call the named method, and asserts that the call throws the expected
   * type of throwable.
   */
  public void callAndAssertThrows(Class<? extends Throwable> expected,
      String methodName, Object... arguments) throws Exception {
    checkNotNull(expected);
    checkNotNull(methodName);
    checkNotNull(arguments);
    sendRequest(methodName, arguments);
    assertEquals(expected, getResponse(methodName).getThrowable().getClass());
  }

  /**
   * Causes this thread to call the named method, and asserts that this thread becomes blocked on
   * the lock-like object. The lock-like object must have a method equivalent to {@link
   * java.util.concurrent.locks.ReentrantLock#hasQueuedThread(Thread)}.
   */
  public void callAndAssertBlocks(String methodName, Object... arguments) throws Exception {
    checkNotNull(methodName);
    checkNotNull(arguments);
    assertEquals(false, invokeMethod("hasQueuedThread", this));
    sendRequest(methodName, arguments);
    Thread.sleep(DUE_DILIGENCE_MILLIS);
    assertEquals(true, invokeMethod("hasQueuedThread", this));
    assertNull(responseQueue.poll());
  }

  /**
   * Causes this thread to call the named method, and asserts that this thread thereby waits on
   * the given condition-like object. The lock-like object must have a method equivalent to {@link
   * java.util.concurrent.locks.ReentrantLock#hasWaiters(java.util.concurrent.locks.Condition)},
   * except that the method parameter must accept whatever condition-like object is passed into
   * this method.
   */
  public void callAndAssertWaits(String methodName, Object conditionLikeObject)
      throws Exception {
    checkNotNull(methodName);
    checkNotNull(conditionLikeObject);
    // TODO: Restore the following line when Monitor.hasWaiters() no longer acquires the lock.
    // assertEquals(false, invokeMethod("hasWaiters", conditionLikeObject));
    sendRequest(methodName, conditionLikeObject);
    Thread.sleep(DUE_DILIGENCE_MILLIS);
    assertEquals(true, invokeMethod("hasWaiters", conditionLikeObject));
    assertNull(responseQueue.poll());
  }

  /**
   * Asserts that a prior call that had caused this thread to block or wait has since returned
   * normally.
   */
  public void assertPriorCallReturns(@Nullable String methodName) throws Exception {
    assertEquals(null, getResponse(methodName).getResult());
  }

  /**
   * Asserts that a prior call that had caused this thread to block or wait has since returned
   * the expected boolean value.
   */
  public void assertPriorCallReturns(boolean expected, @Nullable String methodName)
      throws Exception {
    assertEquals(expected, getResponse(methodName).getResult());
  }

  /**
   * Sends the given method call to this thread.
   *
   * @throws TimeoutException if this thread does not accept the request within a resonable amount
   *         of time
   */
  private void sendRequest(String methodName, Object... arguments) throws Exception {
    if (!requestQueue.offer(
        new Request(methodName, arguments), TIMEOUT_MILLIS, TimeUnit.MILLISECONDS)) {
      throw new TimeoutException();
    }
  }

  /**
   * Receives a response from this thread.
   *
   * @throws TimeoutException if this thread does not offer a response within a resonable amount of
   *         time
   * @throws AssertionFailedError if the given method name does not match the name of the method
   *         this thread has called most recently
   */
  private Response getResponse(String methodName) throws Exception {
    Response response = responseQueue.poll(TIMEOUT_MILLIS, TimeUnit.MILLISECONDS);
    if (response == null) {
      throw new TimeoutException();
    }
    assertEquals(methodName, response.methodName);
    return response;
  }

  private Object invokeMethod(String methodName, Object... arguments) throws Exception {
    return getMethod(methodName, arguments).invoke(lockLikeObject, arguments);
  }

  private Method getMethod(String methodName, Object... arguments) throws Exception {
    METHODS: for (Method method : lockLikeObject.getClass().getMethods()) {
      Class<?>[] parameterTypes = method.getParameterTypes();
      if (method.getName().equals(methodName) && (parameterTypes.length == arguments.length)) {
        for (int i = 0; i < arguments.length; i++) {
          if (!parameterTypes[i].isAssignableFrom(arguments[i].getClass())) {
            continue METHODS;
          }
        }
        return method;
      }
    }
    throw new NoSuchMethodError(methodName);
  }

  @Override public void run() {
    assertSame(this, Thread.currentThread());
    try {
      while (true) {
        Request request = requestQueue.take();
        Object result;
        try {
          result = invokeMethod(request.methodName, request.arguments);
        } catch (ThreadDeath death) {
          return;
        } catch (InvocationTargetException exception) {
          responseQueue.put(
              new Response(request.methodName, null, exception.getTargetException()));
          continue;
        } catch (Throwable throwable) {
          responseQueue.put(new Response(request.methodName, null, throwable));
          continue;
        }
        responseQueue.put(new Response(request.methodName, result, null));
      }
    } catch (ThreadDeath death) {
      return;
    } catch (InterruptedException ignored) {
      // SynchronousQueue sometimes throws InterruptedException while the threads are stopping.
    } catch (Throwable uncaught) {
      this.uncaughtThrowable = uncaught;
    }
  }

  private static class Request {
    final String methodName;
    final Object[] arguments;

    Request(String methodName, Object[] arguments) {
      this.methodName = checkNotNull(methodName);
      this.arguments = checkNotNull(arguments);
    }
  }

  private static class Response {
    final String methodName;
    final Object result;
    final Throwable throwable;

    Response(String methodName, Object result, Throwable throwable) {
      this.methodName = methodName;
      this.result = result;
      this.throwable = throwable;
    }

    Object getResult() {
      if (throwable != null) {
        throw (AssertionFailedError) new AssertionFailedError().initCause(throwable);
      }
      return result;
    }

    Throwable getThrowable() {
      assertNotNull(throwable);
      return throwable;
    }
  }
}

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