test/com/google/inject/CircularDependencyTest.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 junit.framework.TestCase;

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

  public void testCircularlyDependentConstructors()
      throws CreationException {
    Injector injector = Guice.createInjector(new AbstractModule() {
      protected void configure() {
        bind(A.class).to(AImpl.class);
        bind(B.class).to(BImpl.class);
      }
    });

    A a = injector.getInstance(A.class);
    assertNotNull(a.getB().getA());
  }

  interface A {
    B getB();
  }

  @Singleton
  static class AImpl implements A {
    final B b;
    @Inject public AImpl(B b) {
      this.b = b;
    }
    public B getB() {
      return b;
    }
  }

  interface B {
    A getA();
  }

  static class BImpl implements B {
    final A a;
    @Inject public BImpl(A a) {
      this.a = a;
    }
    public A getA() {
      return a;
    }
  }

  public void testUnresolvableCircularDependency() {
    try {
      Guice.createInjector().getInstance(C.class);
      fail();
    } catch (ProvisionException expected) {
      Asserts.assertContains(expected.getMessage(),
          "Tried proxying " + C.class.getName() + " to support a circular dependency, ",
          "but it is not an interface.");
    }
  }

  static class C {
    @Inject C(D d) {}
  }

  static class D {
    @Inject D(C c) {}
  }
}