home | career | drupal | java | mac | mysql | perl | scala | uml | unix  

Java example source code file (EagerSingletonTest.java)

This example Java source code file (EagerSingletonTest.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

abstractmodule, eagersingletontest, inject, injector, object, override, singleton, singletons, testcase

The EagerSingletonTest.java Java example source code

/**
 * Copyright (C) 2008 Google Inc.
 *
 * 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.inject;

import junit.framework.TestCase;

/**
 * @author jessewilson@google.com (Jesse Wilson)
 */
public class EagerSingletonTest extends TestCase {

  @Override public void setUp() {
    A.instanceCount = 0;
    B.instanceCount = 0;
    C.instanceCount = 0;
  }

  public void testJustInTimeEagerSingletons() {
    Guice.createInjector(Stage.PRODUCTION, new AbstractModule() {
      protected void configure() {
        // create a just-in-time binding for A
        getProvider(A.class);

        // create a just-in-time binding for C
        requestInjection(new Object() {
          @Inject void inject(Injector injector) {
            injector.getInstance(C.class);
          }
        });
      }
    });

    assertEquals(1, A.instanceCount);
    assertEquals("Singletons discovered when creating singletons should not be built eagerly",
        0, B.instanceCount);
    assertEquals(1, C.instanceCount);
  }

  public void testJustInTimeSingletonsAreNotEager() {
    Injector injector = Guice.createInjector(Stage.PRODUCTION);
    injector.getProvider(B.class);
    assertEquals(0, B.instanceCount);
  }

  public void testChildEagerSingletons() {
    Injector parent = Guice.createInjector(Stage.PRODUCTION);
    parent.createChildInjector(new AbstractModule() {
      @Override protected void configure() {
        bind(D.class).to(C.class);
      }
    });

    assertEquals(1, C.instanceCount);
  }

  @Singleton
  static class A {
    static int instanceCount = 0;
    int instanceId = instanceCount++;

    @Inject A(Injector injector) {
      injector.getProvider(B.class);
    }
  }

  @Singleton
  static class B {
    static int instanceCount = 0;
    int instanceId = instanceCount++;
  }

  @Singleton
  static class C implements D {
    static int instanceCount = 0;
    int instanceId = instanceCount++;
  }

  private static interface D {}
}

Other Java examples (source code examples)

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



my book on functional programming

 

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.