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Java example source code file (ProviderInjectionTest.java)

This example Java source code file (ProviderInjectionTest.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, bar, baz, count, creationexception, foo, inject, injector, list, override, provider, samplesingleton, string, testcase, util

The ProviderInjectionTest.java Java example source code

/**
 * Copyright (C) 2006 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 static com.google.inject.name.Names.named;

import com.google.inject.name.Named;

import junit.framework.TestCase;

import java.util.Arrays;
import java.util.List;

/**
 * @author crazybob@google.com (Bob Lee)
 */
public class ProviderInjectionTest extends TestCase {

  public void testProviderInjection() throws CreationException {
    Injector injector = Guice.createInjector(new AbstractModule() {
      protected void configure() {
        bind(Bar.class);
        bind(SampleSingleton.class).in(Scopes.SINGLETON);
      }
    });

    Foo foo = injector.getInstance(Foo.class);

    Bar bar = foo.barProvider.get();
    assertNotNull(bar);
    assertNotSame(bar, foo.barProvider.get());

    SampleSingleton singleton = foo.singletonProvider.get();
    assertNotNull(singleton);
    assertSame(singleton, foo.singletonProvider.get());
  }

  /** Test for bug 155. */
  public void testProvidersAreInjectedWhenBound() {
    Module m = new AbstractModule() {
      @Override
      protected void configure() {
        bind(Bar.class).toProvider(new Provider<Bar>() {
          @SuppressWarnings("unused")
          @Inject void cantBeCalled(Baz baz) {
            fail("Can't have called this method since Baz is not bound.");
          }
          public Bar get() {
            return new Bar() {};
          }
        });
      }
    };

    try {
      Guice.createInjector(m);
      fail("Should have thrown a CreationException");
    }
    catch (CreationException expected) {
    }
  }

  /**
   * When custom providers are used at injector creation time, they should be
   * injected before use. In this testcase, we verify that a provider for
   * List.class is injected before it is used.
   */
  public void testProvidersAreInjectedBeforeTheyAreUsed() {
    Injector injector = Guice.createInjector(new AbstractModule() {
      public void configure() {
        // should bind String to "[true]"
        bind(String.class).toProvider(new Provider<String>() {
          private String value;
          @Inject void initialize(List list) {
            value = list.toString();
          }
          public String get() {
            return value;
          }
        });

        // should bind List to [true]
        bind(List.class).toProvider(new Provider<List>() {
          @Inject Boolean injectedYet = Boolean.FALSE;
          public List get() {
            return Arrays.asList(injectedYet);
          }
        });

        // should bind Boolean to true
        bind(Boolean.class).toInstance(Boolean.TRUE);
      }
    });

    assertEquals("Providers not injected before use",
        "[true]",
        injector.getInstance(String.class));
  }

  /**
   * This test ensures that regardless of binding order, instances are injected
   * before they are used. It injects mutable Count objects and records their
   * value at the time that they're injected.
   */
  public void testCreationTimeInjectionOrdering() {
    Injector injector = Guice.createInjector(new AbstractModule() {
      protected void configure() {
        // instance injection
        bind(Count.class).annotatedWith(named("a")).toInstance(new Count(0) {
          @Inject void initialize(@Named("b") Count bCount) {
            value = bCount.value + 1;
          }
        });

        // provider injection
        bind(Count.class).annotatedWith(named("b")).toProvider(new Provider<Count>() {
          Count count;
          @Inject void initialize(@Named("c") Count cCount) {
            count = new Count(cCount.value + 2);
          }
          public Count get() {
            return count;
          }
        });

        // field and method injection, fields first
        bind(Count.class).annotatedWith(named("c")).toInstance(new Count(0) {
          @Inject @Named("d") Count dCount;
          @Inject void initialize(@Named("e") Count eCount) {
            value = dCount.value + eCount.value + 4;
          }
        });

        // static injection
        requestStaticInjection(StaticallyInjectable.class);

        bind(Count.class).annotatedWith(named("d")).toInstance(new Count(8));
        bind(Count.class).annotatedWith(named("e")).toInstance(new Count(16));
      }
    });

    assertEquals(28, injector.getInstance(Key.get(Count.class, named("c"))).value);
    assertEquals(30, injector.getInstance(Key.get(Count.class, named("b"))).value);
    assertEquals(31, injector.getInstance(Key.get(Count.class, named("a"))).value);
    assertEquals(28, StaticallyInjectable.cCountAtInjectionTime);
  }

  static class Count {
    int value;
    Count(int value) {
      this.value = value;
    }
  }

  static class StaticallyInjectable {
    static int cCountAtInjectionTime;
    @Inject static void initialize(@Named("c") Count cCount) {
      cCountAtInjectionTime = cCount.value;
    }
  }

  static class Foo {
    @Inject Provider<Bar> barProvider;
    @Inject Provider<SampleSingleton> singletonProvider;
  }

  static class Bar {}

  static class SampleSingleton {}

  interface Baz { }

}

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