Java example source code file (ForwardingObjectTester.java)

This example Java source code file (ForwardingObjectTester.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, class, delegate_method, forwardingobject, forwardingobjecttester, function, method, nosuchmethodexception, override, reflection, runtimeexception, securityexception, suppresswarnings, util

The ForwardingObjectTester.java Java example source code

/*
 * Copyright (C) 2012 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 org.mockito.Answers.CALLS_REAL_METHODS;
import static org.mockito.Mockito.doReturn;
import static org.mockito.Mockito.mock;

import com.google.common.base.Function;
import com.google.common.base.Throwables;
import com.google.common.collect.ForwardingObject;
import com.google.common.collect.Iterables;
import com.google.common.testing.ForwardingWrapperTester;

import java.lang.reflect.Method;
import java.util.Arrays;

/**
 * Tester for typical subclass of {@link ForwardingObject} by using EasyMock partial mocks.
 *
 * @author Ben Yu
 */
final class ForwardingObjectTester {

  private static final Method DELEGATE_METHOD;
  static {
    try {
      DELEGATE_METHOD = ForwardingObject.class.getDeclaredMethod("delegate");
      DELEGATE_METHOD.setAccessible(true);
    } catch (SecurityException e) {
      throw new RuntimeException(e);
    } catch (NoSuchMethodException e) {
      throw new AssertionError(e);
    }
  }

  /**
   * Ensures that all interface methods of {@code forwarderClass} are forwarded to the
   * {@link ForwardingObject#delegate}. {@code forwarderClass} is assumed to only implement one
   * interface.
   */
  static <T extends ForwardingObject> void testForwardingObject(final Class forwarderClass) {
    @SuppressWarnings("unchecked") // super interface type of T
    Class<? super T> interfaceType = (Class)
        Iterables.getOnlyElement(Arrays.asList(forwarderClass.getInterfaces()));
    new ForwardingWrapperTester().testForwarding(interfaceType, new Function<Object, T>() {
      @Override public T apply(Object delegate) {
        T mock = mock(forwarderClass, CALLS_REAL_METHODS.get());
        try {
          T stubber = doReturn(delegate).when(mock);
          DELEGATE_METHOD.invoke(stubber);
        } catch (Exception e) {
          throw Throwables.propagate(e);
        }
        return mock;
      }
    });
  }
}