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Java example source code file (SubscriberTest.java)

This example Java source code file (SubscriberTest.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

equalstester, eventbus, exception, fixture_argument, intentionalexception, invocationtargetexception, judgmenterror, method, object, reflection, subscribe, subscriber, subscribers, testcase, throwable

The SubscriberTest.java Java example source code

/*
 * Copyright (C) 2007 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.testing.EqualsTester;

import junit.framework.TestCase;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

/**
 * Tests for {@link Subscriber}.
 *
 * @author Cliff Biffle
 * @author Colin Decker
 */
public class SubscriberTest extends TestCase {

  private static final Object FIXTURE_ARGUMENT = new Object();

  private EventBus bus;
  private boolean methodCalled;
  private Object methodArgument;

  @Override
  protected void setUp() throws Exception {
    bus = new EventBus();
    methodCalled = false;
    methodArgument = null;
  }

  public void testCreate() {
    Subscriber s1 = Subscriber.create(bus, this, getTestSubscriberMethod("recordingMethod"));
    assertThat(s1).isInstanceOf(Subscriber.SynchronizedSubscriber.class);

    // a thread-safe method should not create a synchronized subscriber
    Subscriber s2 = Subscriber.create(bus, this, getTestSubscriberMethod("threadSafeMethod"));
    assertThat(s2).isNotInstanceOf(Subscriber.SynchronizedSubscriber.class);
  }

  public void testInvokeSubscriberMethod_basicMethodCall() throws Throwable {
    Method method = getTestSubscriberMethod("recordingMethod");
    Subscriber subscriber = Subscriber.create(bus, this, method);

    subscriber.invokeSubscriberMethod(FIXTURE_ARGUMENT);

    assertTrue("Subscriber must call provided method", methodCalled);
    assertTrue("Subscriber argument must be exactly the provided object.",
        methodArgument == FIXTURE_ARGUMENT);
  }

  public void testInvokeSubscriberMethod_exceptionWrapping() throws Throwable {
    Method method = getTestSubscriberMethod("exceptionThrowingMethod");
    Subscriber subscriber = Subscriber.create(bus, this, method);

    try {
      subscriber.invokeSubscriberMethod(FIXTURE_ARGUMENT);
      fail("Subscribers whose methods throw must throw InvocationTargetException");
    } catch (InvocationTargetException expected) {
      assertThat(expected.getCause()).isInstanceOf(IntentionalException.class);
    }
  }

  public void testInvokeSubscriberMethod_errorPassthrough() throws Throwable {
    Method method = getTestSubscriberMethod("errorThrowingMethod");
    Subscriber subscriber = Subscriber.create(bus, this, method);

    try {
      subscriber.invokeSubscriberMethod(FIXTURE_ARGUMENT);
      fail("Subscribers whose methods throw Errors must rethrow them");
    } catch (JudgmentError expected) {
    }
  }

  public void testEquals() throws Exception {
    Method charAt = String.class.getMethod("charAt", int.class);
    Method concat = String.class.getMethod("concat", String.class);
    new EqualsTester()
        .addEqualityGroup(
            Subscriber.create(bus, "foo", charAt), Subscriber.create(bus, "foo", charAt))
        .addEqualityGroup(Subscriber.create(bus, "bar", charAt))
        .addEqualityGroup(Subscriber.create(bus, "foo", concat))
        .testEquals();
  }

  private Method getTestSubscriberMethod(String name) {
    try {
      return getClass().getDeclaredMethod(name, Object.class);
    } catch (NoSuchMethodException e) {
      throw new AssertionError();
    }
  }

  /**
   * Records the provided object in {@link #methodArgument} and sets {@link #methodCalled}.  This
   * method is called reflectively by Subscriber during tests, and must remain public.
   *
   * @param arg argument to record.
   */
  @Subscribe
  public void recordingMethod(Object arg) {
    assertFalse(methodCalled);
    methodCalled = true;
    methodArgument = arg;
  }

  @Subscribe
  public void exceptionThrowingMethod(Object arg) throws Exception {
    throw new IntentionalException();
  }

  /**
   * Local exception subclass to check variety of exception thrown.
   */
  class IntentionalException extends Exception {

    private static final long serialVersionUID = -2500191180248181379L;
  }

  @Subscribe
  public void errorThrowingMethod(Object arg) {
    throw new JudgmentError();
  }

  @Subscribe @AllowConcurrentEvents
  public void threadSafeMethod(Object arg) {
  }

  /**
   * Local Error subclass to check variety of error thrown.
   */
  class JudgmentError extends Error {

    private static final long serialVersionUID = 634248373797713373L;
  }
}

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