Java example source code file (AbstractFutureCancellationCauseTest.java)

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Java - Java tags/keywords

abstractfuturecancellationcausetest, cancellationexception, classnotfoundexception, exception, expected, future, net, network, override, settablefuture, string, testcase, threading, threads, urlclassloader

The AbstractFutureCancellationCauseTest.java Java example source code

/*
 * Copyright (C) 2015 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 junit.framework.TestCase;

import java.net.URLClassLoader;
import java.util.concurrent.CancellationException;
import java.util.concurrent.Future;

/**
 * Tests for {@link AbstractFuture} with the cancellation cause system property set
 */

public class AbstractFutureCancellationCauseTest extends TestCase {

  private ClassLoader oldClassLoader;
  private URLClassLoader classReloader;

  @Override protected void setUp() throws Exception {
    // Load the "normal" copy of SettableFuture and related classes.
    SettableFuture<?> unused = SettableFuture.create();
    // Hack to load AbstractFuture et. al. in a new classloader so that it re-reads the cancellation
    // cause system property.  This allows us to run with both settings of the property in one jvm
    // without resorting to even crazier hacks to reset static final boolean fields.
    System.setProperty("guava.concurrent.generate_cancellation_cause", "true");
    final String concurrentPackage = SettableFuture.class.getPackage().getName();
    classReloader =
        new URLClassLoader(((URLClassLoader) SettableFuture.class.getClassLoader()).getURLs()) {
          @Override public Class<?> loadClass(String name) throws ClassNotFoundException {
            if (name.startsWith(concurrentPackage)) {
              return super.findClass(name);
            }
            return super.loadClass(name);
          }
        };
    oldClassLoader = Thread.currentThread().getContextClassLoader();
    Thread.currentThread().setContextClassLoader(classReloader);
  }

  @Override
  protected void tearDown() throws Exception {
    classReloader.close();
    Thread.currentThread().setContextClassLoader(oldClassLoader);
    System.clearProperty("guava.concurrent.generate_cancellation_cause");
  }

  public void testCancel_notDoneNoInterrupt() throws Exception {
    Future<?> future = newFutureInstance();
    assertTrue(future.cancel(false));
    assertTrue(future.isCancelled());
    assertTrue(future.isDone());
    try {
      future.get();
      fail("Expected CancellationException");
    } catch (CancellationException e) {
      assertNotNull(e.getCause());
    }
  }

  public void testCancel_notDoneInterrupt() throws Exception {
    Future<?> future = newFutureInstance();
    assertTrue(future.cancel(true));
    assertTrue(future.isCancelled());
    assertTrue(future.isDone());
    try {
      future.get();
      fail("Expected CancellationException");
    } catch (CancellationException e) {
      assertNotNull(e.getCause());
    }
  }

  private Future<?> newFutureInstance() throws Exception {
    return (Future<?>)
        classReloader.loadClass(SettableFuture.class.getName()).getMethod("create").invoke(null);
  }
}