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. By default, an 21 * instance created by the {@link Injector} has <i>no scope</i>, meaning it has no state from the 22 * framework's perspective -- the {@code Injector} creates it, injects it once into the class that 23 * required it, and then immediately forgets it. Associating a scope with a particular binding 24 * allows the created instance to be "remembered" and possibly used again for other injections. 25 * 26 * <p>An example of a scope is {@link Scopes#SINGLETON}. 27 * 28 * @author crazybob (at) google.com (Bob Lee) 29 */ 30 public interface Scope { 31 32 /** 33 * Scopes a provider. The returned provider returns objects from this scope. If an object does not 34 * exist in this scope, the provider can use the given unscoped provider to retrieve one. 35 * 36 * <p>Scope implementations are strongly encouraged to override {@link Object#toString} in the 37 * returned provider and include the backing provider's {@code toString()} output. 38 * 39 * @param key binding key 40 * @param unscoped locates an instance when one doesn't already exist in this scope. 41 * @return a new provider which only delegates to the given unscoped provider when an instance of 42 * the requested object doesn't already exist in this scope 43 */ 44 public <T> Provider<T> scope(Key<T> key, Provider<T> unscoped); 45 46 /** 47 * A short but useful description of this scope. For comparison, the standard scopes that ship 48 * with guice use the descriptions {@code "Scopes.SINGLETON"}, {@code "ServletScopes.SESSION"} and 49 * {@code "ServletScopes.REQUEST"}. 50 */ 51 @Override 52 String toString(); 53 } 54
