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/*
* 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 {@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 {
* @Inject Car(Provider<Seat> seatProvider) {
* Seat driver = seatProvider.get();
* Seat passenger = seatProvider.get();
* ...
* }
* }</pre>
*/
public interface Provider<T> {
/**
* 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();
}
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