1 /** 2 * Copyright (C) 2006 Google Inc. 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.google.inject; 18 19 /** 20 * A scope is a level of visibility that instances provided by Guice may have. 21 * By default, an instance created by the {@link Injector} has <i>no scope</i>, 22 * meaning it has no state from the framework's perspective -- the 23 * {@code Injector} creates it, injects it once into the class that required it, 24 * and then immediately forgets it. Associating a scope with a particular 25 * binding allows the created instance to be "remembered" and possibly used 26 * again for other injections. 27 * 28 * <p>An example of a scope is {@link Scopes#SINGLETON}. 29 * 30 * @author crazybob (at) google.com (Bob Lee) 31 */ 32 public interface Scope { 33 34 /** 35 * Scopes a provider. The returned provider returns objects from this scope. 36 * If an object does not exist in this scope, the provider can use the given 37 * unscoped provider to retrieve one. 38 * 39 * <p>Scope implementations are strongly encouraged to override 40 * {@link Object#toString} in the returned provider and include the backing 41 * provider's {@code toString()} output. 42 * 43 * @param key binding key 44 * @param unscoped locates an instance when one doesn't already exist in this 45 * scope. 46 * @return a new provider which only delegates to the given unscoped provider 47 * when an instance of the requested object doesn't already exist in this 48 * scope 49 */ 50 public <T> Provider<T> scope(Key<T> key, Provider<T> unscoped); 51 52 /** 53 * A short but useful description of this scope. For comparison, the standard 54 * scopes that ship with guice use the descriptions 55 * {@code "Scopes.SINGLETON"}, {@code "ServletScopes.SESSION"} and 56 * {@code "ServletScopes.REQUEST"}. 57 */ 58 String toString(); 59 } 60
