src/com/google/inject/ConstructorInjector.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 com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableSet;
import com.google.inject.internal.Errors;
import com.google.inject.internal.ErrorsException;
import com.google.inject.spi.InjectionPoint;
import java.lang.reflect.InvocationTargetException;

/**
 * Creates instances using an injectable constructor. After construction, all injectable fields and
 * methods are injected.
 *
 * @author crazybob@google.com (Bob Lee)
 */
class ConstructorInjector<T> {

  final TypeLiteral<T> implementation;
  final InjectionPoint injectionPoint;
  final ImmutableList<SingleMemberInjector> memberInjectors;
  final ImmutableList<SingleParameterInjector<?>> parameterInjectors;
  final ConstructionProxy<T> constructionProxy;

  ConstructorInjector(Errors errors, InjectorImpl injector, TypeLiteral<T> implementation)
      throws ErrorsException {
    this.implementation = implementation;

    try {
      this.injectionPoint = InjectionPoint.forConstructorOf(implementation);
    } catch (ConfigurationException e) {
      throw errors.merge(e.getErrorMessages()).toException();
    }

    constructionProxy = injector.constructionProxyFactory.get(injectionPoint);
    parameterInjectors = injector.getParametersInjectors(injectionPoint.getDependencies(), errors);
    memberInjectors = injector.injectors.get(implementation, errors);
  }

  ImmutableSet<InjectionPoint> getInjectionPoints() {
    InjectionPoint[] injectionPoints = new InjectionPoint[memberInjectors.size() + 1];
    injectionPoints[0] = constructionProxy.getInjectionPoint();
    int i = 1;
    for (SingleMemberInjector memberInjector : memberInjectors) {
      injectionPoints[i++] = memberInjector.getInjectionPoint();
    }
    return ImmutableSet.of(injectionPoints);
  }

  /**
   * Construct an instance. Returns {@code Object} instead of {@code T} because
   * it may return a proxy.
   */
  Object construct(Errors errors, InternalContext context, Class<?> expectedType)
      throws ErrorsException {
    ConstructionContext<T> constructionContext = context.getConstructionContext(this);

    // We have a circular reference between constructors. Return a proxy.
    if (constructionContext.isConstructing()) {
      // TODO (crazybob): if we can't proxy this object, can we proxy the other object?
      return constructionContext.createProxy(errors, expectedType);
    }

    // If we're re-entering this factory while injecting fields or methods,
    // return the same instance. This prevents infinite loops.
    T t = constructionContext.getCurrentReference();
    if (t != null) {
      return t;
    }

    try {
      // First time through...
      constructionContext.startConstruction();
      try {
        Object[] parameters = SingleParameterInjector.getAll(errors, context, parameterInjectors);
        t = constructionProxy.newInstance(parameters);
        constructionContext.setProxyDelegates(t);
      } finally {
        constructionContext.finishConstruction();
      }

      // Store reference. If an injector re-enters this factory, they'll
      // get the same reference.
      constructionContext.setCurrentReference(t);

      // Inject fields and methods.
      for (SingleMemberInjector injector : memberInjectors) {
        injector.inject(errors, context, t);
      }

      return t;
    } catch (InvocationTargetException userException) {
      Throwable cause = userException.getCause() != null
          ? userException.getCause()
          : userException;
      throw errors.withSource(constructionProxy.getInjectionPoint())
          .errorInjectingConstructor(cause).toException();
    } finally {
      constructionContext.removeCurrentReference();
    }
  }
}