core/src/com/google/inject/internal/SingleParameterInjector.java

/*
 * 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.internal;

import com.google.inject.spi.Dependency;

/** Resolves a single parameter, to be used in a constructor or method invocation. */
final class SingleParameterInjector<T> {
  private static final Object[] NO_ARGUMENTS = {};

  private final Dependency<T> dependency;

  private final Object source;

  private final InternalFactory<? extends T> factory;

  SingleParameterInjector(Dependency<T> dependency, BindingImpl<? extends T> binding) {
    this.dependency = dependency;
    this.source = binding.getSource();
    this.factory = binding.getInternalFactory();
  }

  T inject(InternalContext context) throws InternalProvisionException {
    Dependency<T> localDependency = dependency;
    Dependency previous = context.pushDependency(localDependency, source);

    try {
      return factory.get(context, localDependency, false);
    } catch (InternalProvisionException ipe) {
      throw ipe.addSource(localDependency);
      } finally {
        context.popStateAndSetDependency(previous);

    }
  }

  // TODO(lukes): inline into callers to decrease stack depth

  /** Returns an array of parameter values. */
  static Object[] getAll(InternalContext context, SingleParameterInjector<?>[] parameterInjectors)
      throws InternalProvisionException {
    if (parameterInjectors == null) {
      return NO_ARGUMENTS;
    }

    int size = parameterInjectors.length;
    Object[] parameters = new Object[size];

    // optimization: use manual for/each to save allocating an iterator here
    for (int i = 0; i < size; i++) {
      parameters[i] = parameterInjectors[i].inject(context);
    }
    return parameters;
  }
}