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58 lines
2.0 KiB
58 lines
2.0 KiB
5 years ago
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/*
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* Copyright (C) 2009 The JSR-330 Expert Group
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package javax.inject;
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/**
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* Provides instances of {@code T}. Typically implemented by an injector. For
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* any type {@code T} that can be injected, you can also inject
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* {@code Provider<T>}. Compared to injecting {@code T} directly, injecting
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* {@code Provider<T>} enables:
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*
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* <ul>
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* <li>retrieving multiple instances.</li>
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* <li>lazy or optional retrieval of an instance.</li>
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* <li>breaking circular dependencies.</li>
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* <li>abstracting scope so you can look up an instance in a smaller scope
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* from an instance in a containing scope.</li>
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* </ul>
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*
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* <p>For example:
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*
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* <pre>
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* class Car {
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* @Inject Car(Provider<Seat> seatProvider) {
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* Seat driver = seatProvider.get();
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* Seat passenger = seatProvider.get();
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* ...
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* }
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* }</pre>
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*/
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public interface Provider<T> {
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/**
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* Provides a fully-constructed and injected instance of {@code T}.
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*
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* @throws RuntimeException if the injector encounters an error while
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* providing an instance. For example, if an injectable member on
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* {@code T} throws an exception, the injector may wrap the exception
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* and throw it to the caller of {@code get()}. Callers should not try
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* to handle such exceptions as the behavior may vary across injector
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* implementations and even different configurations of the same injector.
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*/
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T get();
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}
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