/*
 * Copyright (C) 2009 The JSR-330 Expert Group
 *
 * 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 javax.inject;

Provides instances of T. Typically implemented by an injector. For any type T that can be injected, you can also inject Provider<T>. Compared to injecting T directly, injecting Provider<T> enables: 

  
retrieving multiple instances.
  
lazy or optional retrieval of an instance.
  
breaking circular dependencies.
  
abstracting scope so you can look up an instance in a smaller scope
     from an instance in a containing scope.

For example:
  class Car {
    @Inject Car(Provider<Seat> seatProvider) {
      Seat driver = seatProvider.get();
      Seat passenger = seatProvider.get();
      ...
    }
  }
/**
 * Provides instances of {@code T}. Typically implemented by an injector. For
 * any type {@code T} that can be injected, you can also inject
 * {@code Provider<T>}. Compared to injecting {@code T} directly, injecting
 * {@code Provider<T>} enables:
 *
 * <ul>
 *   <li>retrieving multiple instances.</li>
 *   <li>lazy or optional retrieval of an instance.</li>
 *   <li>breaking circular dependencies.</li>
 *   <li>abstracting scope so you can look up an instance in a smaller scope
 *      from an instance in a containing scope.</li>
 * </ul>
 *
 * <p>For example:
 *
 * <pre>
 *   class Car {
 *     &#064;Inject Car(Provider&lt;Seat> seatProvider) {
 *       Seat driver = seatProvider.get();
 *       Seat passenger = seatProvider.get();
 *       ...
 *     }
 *   }</pre>
 */
public interface Provider<T> {

    
Provides a fully-constructed and injected instance of T. 
Throws:
RuntimeException – if the injector encounters an error while providing an instance. For example, if an injectable member on T throws an exception, the injector may wrap the exception and throw it to the caller of get(). Callers should not try to handle such exceptions as the behavior may vary across injector implementations and even different configurations of the same injector./**
     * Provides a fully-constructed and injected instance of {@code T}.
     *
     * @throws RuntimeException if the injector encounters an error while
     *  providing an instance. For example, if an injectable member on
     *  {@code T} throws an exception, the injector may wrap the exception
     *  and throw it to the caller of {@code get()}. Callers should not try
     *  to handle such exceptions as the behavior may vary across injector
     *  implementations and even different configurations of the same injector.
     */
    T get();
}