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Java example source code file (DispatcherTest.java)

This example Java source code file (DispatcherTest.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

assertionerror, countdownlatch, cyclicbarrier, dispatcher, eventbus, exception, immutablelist, integersubscriber, nosuchmethodexception, object, override, runnable, string, stringsubscriber, threading, threads

The DispatcherTest.java Java example source code

/*
 * Copyright (C) 2014 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.eventbus;

import static com.google.common.truth.Truth.assertThat;

import com.google.common.collect.ImmutableList;
import com.google.common.collect.Queues;
import com.google.common.util.concurrent.Uninterruptibles;

import junit.framework.TestCase;

import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.CyclicBarrier;

/**
 * Tests for {@link Dispatcher} implementations.
 *
 * @author Colin Decker
 */

public class DispatcherTest extends TestCase {

  private final EventBus bus = new EventBus();

  private final IntegerSubscriber i1 = new IntegerSubscriber("i1");
  private final IntegerSubscriber i2 = new IntegerSubscriber("i2");
  private final IntegerSubscriber i3 = new IntegerSubscriber("i3");
  private final ImmutableList<Subscriber> integerSubscribers = ImmutableList.of(
      subscriber(bus, i1, "handleInteger", Integer.class),
      subscriber(bus, i2, "handleInteger", Integer.class),
      subscriber(bus, i3, "handleInteger", Integer.class));

  private final StringSubscriber s1 = new StringSubscriber("s1");
  private final StringSubscriber s2 = new StringSubscriber("s2");
  private final ImmutableList<Subscriber> stringSubscribers = ImmutableList.of(
      subscriber(bus, s1, "handleString", String.class),
      subscriber(bus, s2, "handleString", String.class));

  private final ConcurrentLinkedQueue<Object> dispatchedSubscribers
      = Queues.newConcurrentLinkedQueue();

  private Dispatcher dispatcher;

  public void testPerThreadQueuedDispatcher() {
    dispatcher = Dispatcher.perThreadDispatchQueue();
    dispatcher.dispatch(1, integerSubscribers.iterator());

    assertThat(dispatchedSubscribers)
        .containsExactly(
            i1, i2, i3, // Integer subscribers are dispatched to first.
            s1, s2,     // Though each integer subscriber dispatches to all string subscribers,
            s1, s2,     // those string subscribers aren't actually dispatched to until all integer
            s1, s2      // subscribers have finished.
        ).inOrder();
  }

  public void testLegacyAsyncDispatcher() {
    dispatcher = Dispatcher.legacyAsync();

    final CyclicBarrier barrier = new CyclicBarrier(2);
    final CountDownLatch latch = new CountDownLatch(2);

    new Thread(new Runnable() {
      @Override
      public void run() {
        try {
          barrier.await();
        } catch (Exception e) {
          throw new AssertionError(e);
        }

        dispatcher.dispatch(2, integerSubscribers.iterator());
        latch.countDown();
      }
    }).start();

    new Thread(new Runnable() {
      @Override
      public void run() {
        try {
          barrier.await();
        } catch (Exception e) {
          throw new AssertionError(e);
        }

        dispatcher.dispatch("foo", stringSubscribers.iterator());
        latch.countDown();
      }
    }).start();

    Uninterruptibles.awaitUninterruptibly(latch);

    // See Dispatcher.LegacyAsyncDispatcher for an explanation of why there aren't really any
    // useful testable guarantees about the behavior of that dispatcher in a multithreaded
    // environment. Here we simply test that all the expected dispatches happened in some order.
    assertThat(dispatchedSubscribers)
        .containsExactly(
            i1, i2, i3,
            s1, s1, s1, s1,
            s2, s2, s2, s2);
  }

  public void testImmediateDispatcher() {
    dispatcher = Dispatcher.immediate();
    dispatcher.dispatch(1, integerSubscribers.iterator());

    assertThat(dispatchedSubscribers)
        .containsExactly(
            i1, s1, s2,  // Each integer subscriber immediately dispatches to 2 string subscribers.
            i2, s1, s2,
            i3, s1, s2
        ).inOrder();
  }

  private static Subscriber subscriber(
      EventBus bus, Object target,
      String methodName, Class<?> eventType) {
    try {
      return Subscriber.create(bus, target, target.getClass().getMethod(methodName, eventType));
    } catch (NoSuchMethodException e) {
      throw new AssertionError(e);
    }
  }

  public final class IntegerSubscriber {
    private final String name;

    public IntegerSubscriber(String name) {
      this.name = name;
    }

    @Subscribe
    public void handleInteger(Integer integer) {
      dispatchedSubscribers.add(this);
      dispatcher.dispatch("hello", stringSubscribers.iterator());
    }

    @Override
    public String toString() {
      return name;
    }
  }

  public final class StringSubscriber {
    private final String name;

    public StringSubscriber(String name) {
      this.name = name;
    }

    @Subscribe
    public void handleString(String string) {
      dispatchedSubscribers.add(this);
    }

    @Override
    public String toString() {
      return name;
    }
  }
}

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