alvinalexander.com | career | drupal | java | mac | mysql | perl | scala | uml | unix  

Java example source code file (FinalizableReferenceQueueTest.java)

This example Java source code file (FinalizableReferenceQueueTest.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

androidincompatible, class, classnotfoundexception, decoupledclassloader, exception, finalizablereferencequeue, finalizableweakreference, how, mockreference, net, network, object, override, testcase, todo, urlclassloader, util

The FinalizableReferenceQueueTest.java Java example source code

/*
 * Copyright (C) 2005 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.base;

import com.google.common.base.internal.Finalizer;
import com.google.common.testing.GcFinalization;

import junit.framework.TestCase;

import java.lang.ref.ReferenceQueue;
import java.lang.ref.WeakReference;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.Arrays;
import java.util.Collections;

/**
 * Unit test for {@link FinalizableReferenceQueue}.
 *
 * @author Bob Lee
 */
public class FinalizableReferenceQueueTest extends TestCase {

  private FinalizableReferenceQueue frq;

  @Override
  protected void tearDown() throws Exception {
    frq = null;
  }

  public void testFinalizeReferentCalled() {
    final MockReference reference = new MockReference(
        frq = new FinalizableReferenceQueue());

    GcFinalization.awaitDone(new GcFinalization.FinalizationPredicate() {
        public boolean isDone() {
          return reference.finalizeReferentCalled;
        }
      });
  }

  static class MockReference extends FinalizableWeakReference<Object> {

    volatile boolean finalizeReferentCalled;

    MockReference(FinalizableReferenceQueue frq) {
      super(new Object(), frq);
    }

    @Override
    public void finalizeReferent() {
      finalizeReferentCalled = true;
    }
  }

  /**
   * Keeps a weak reference to the underlying reference queue. When this
   * reference is cleared, we know that the background thread has stopped
   * and released its strong reference.
   */
  private WeakReference<ReferenceQueue queueReference;

  public void testThatFinalizerStops() {
    weaklyReferenceQueue();
    GcFinalization.awaitClear(queueReference);
  }

  /**
   * If we don't keep a strong reference to the reference object, it won't
   * be enqueued.
   */
  FinalizableWeakReference<Object> reference;

  /**
   * Create the FRQ in a method that goes out of scope so that we're sure
   * it will be reclaimed.
   */
  private void weaklyReferenceQueue() {
    frq = new FinalizableReferenceQueue();
    queueReference = new WeakReference<ReferenceQueue(frq.queue);

    /*
     * Queue and clear a reference for good measure. We test later on that
     * the finalizer thread stopped, but we should test that it actually
     * started first.
     */
    reference = new FinalizableWeakReference<Object>(new Object(), frq) {
      @Override
      public void finalizeReferent() {
        reference = null;
        frq = null;
      }
    };
  }

  @AndroidIncompatible // no concept of separate ClassLoaders
  public void testDecoupledLoader() {
    FinalizableReferenceQueue.DecoupledLoader decoupledLoader =
        new FinalizableReferenceQueue.DecoupledLoader() {
          @Override
          URLClassLoader newLoader(URL base) {
            return new DecoupledClassLoader(new URL[] { base });
          }
        };

    Class<?> finalizerCopy = decoupledLoader.loadFinalizer();

    assertNotNull(finalizerCopy);
    assertNotSame(Finalizer.class, finalizerCopy);

    assertNotNull(FinalizableReferenceQueue.getStartFinalizer(finalizerCopy));
  }

  static class DecoupledClassLoader extends URLClassLoader {

    public DecoupledClassLoader(URL[] urls) {
      super(urls);
    }

    @Override
    protected synchronized Class<?> loadClass(String name, boolean resolve)
        throws ClassNotFoundException {
      // Force Finalizer to load from this class loader, not its parent.
      if (name.equals(Finalizer.class.getName())) {
        Class<?> clazz = findClass(name);
        if (resolve) {
          resolveClass(clazz);
        }
        return clazz;
      }

      return super.loadClass(name, resolve);
    }
  }

  @AndroidIncompatible // TODO(cpovirk): How significant is this failure?
  public void testGetFinalizerUrl() {
    assertNotNull(getClass().getResource("internal/Finalizer.class"));
  }

  public void testFinalizeClassHasNoNestedClases() throws Exception {
    // Ensure that the Finalizer class has no nested classes.
    // See https://code.google.com/p/guava-libraries/issues/detail?id=1505
    assertEquals(Collections.emptyList(), Arrays.asList(Finalizer.class.getDeclaredClasses()));
  }
}

Other Java examples (source code examples)

Here is a short list of links related to this Java FinalizableReferenceQueueTest.java source code file:

... this post is sponsored by my books ...

#1 New Release!

FP Best Seller

 

new blog posts

 

Copyright 1998-2021 Alvin Alexander, alvinalexander.com
All Rights Reserved.

A percentage of advertising revenue from
pages under the /java/jwarehouse URI on this website is
paid back to open source projects.