ProviderInjectionTest.java

/*
 * 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 java.util.Arrays;
import java.util.List;
import junit.framework.TestCase;

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

  public void testProviderInjection() throws CreationException {
    Injector injector =
        Guice.createInjector(
            new AbstractModule() {
              @Override
              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.");
                      }

                      @Override
                      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() {
              @Override
              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();
                          }

                          @Override
                          public String get() {
                            return value;
                          }
                        });

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

                          @Override
                          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() {
              @Override
              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);
                          }

                          @Override
                          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 {}
}