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Java example source code file (SingleParameterInjector.java)

This example Java source code file (SingleParameterInjector.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

bindingimpl, dependency, errorsexception, internalcontext, no_arguments, object, singleparameterinjector

The SingleParameterInjector.java Java example source code

/**
 * 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 BindingImpl<? extends T> binding;

  SingleParameterInjector(Dependency<T> dependency, BindingImpl binding) {
    this.dependency = dependency;
    this.binding = binding;
  }

  private T inject(Errors errors, InternalContext context) throws ErrorsException {
    Dependency previous = context.pushDependency(dependency, binding.getSource());
    try {
      return binding.getInternalFactory().get(errors.withSource(dependency), context, dependency, false);
    } finally {
      context.popStateAndSetDependency(previous);
    }
  }

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

    int numErrorsBefore = errors.size();

    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++) {
      SingleParameterInjector<?> parameterInjector = parameterInjectors[i];
      try {
        parameters[i] = parameterInjector.inject(errors, context);
      } catch (ErrorsException e) {
        errors.merge(e.getErrors());
      }
    }

    errors.throwIfNewErrors(numErrorsBefore);
    return parameters;
  }
}

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