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/**
 * Copyright (C) 2006 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;

/**
 * An object capable of providing instances of type {@code T}. Providers are used in numerous ways
 * by Guice:
 *
 * 
    *
  • When the default means for obtaining instances (an injectable or parameterless constructor) * is insufficient for a particular binding, the module can specify a custom {@code Provider} * instead, to control exactly how Guice creates or obtains instances for the binding. * *
  • An implementation class may always choose to have a {@code Provider} instance injected, * rather than having a {@code T} injected directly. This may give you access to multiple * instances, instances you wish to safely mutate and discard, instances which are out of scope * (e.g. using a {@code @RequestScoped} object from within a {@code @SessionScoped} object), or * instances that will be initialized lazily. * *
  • A custom {@link Scope} is implemented as a decorator of {@code Provider}, which decides * when to delegate to the backing provider and when to provide the instance some other way. * *
  • The {@link Injector} offers access to the {@code Provider} it uses to fulfill requests * for a given key, via the {@link Injector#getProvider} methods. *
* * @param the type of object this provides * * @author [email protected] (Bob Lee) */ public interface Provider extends javax.inject.Provider { /** * Provides an instance of {@code T}. Must never return {@code null}. * * @throws OutOfScopeException when an attempt is made to access a scoped object while the scope * in question is not currently active * @throws ProvisionException if an instance cannot be provided. Such exceptions include messages * and throwables to describe why provision failed. */ T get(); }




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