| /** |
| * 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; |
| |
| import com.google.inject.internal.Errors; |
| import java.lang.annotation.Annotation; |
| |
| /** |
| * Built in scope implementations. |
| * |
| * @author crazybob@google.com (Bob Lee) |
| */ |
| public class Scopes { |
| |
| private Scopes() {} |
| |
| /** |
| * One instance per {@link Injector}. Also see {@code @}{@link Singleton}. |
| */ |
| public static final Scope SINGLETON = new Scope() { |
| public <T> Provider<T> scope(Key<T> key, final Provider<T> creator) { |
| return new Provider<T>() { |
| |
| private volatile T instance; |
| |
| // DCL on a volatile is safe as of Java 5, which we obviously require. |
| @SuppressWarnings("DoubleCheckedLocking") |
| public T get() { |
| if (instance == null) { |
| /* |
| * Use a pretty coarse lock. We don't want to run into deadlocks |
| * when two threads try to load circularly-dependent objects. |
| * Maybe one of these days we will identify independent graphs of |
| * objects and offer to load them in parallel. |
| */ |
| synchronized (Injector.class) { |
| if (instance == null) { |
| instance = creator.get(); |
| } |
| } |
| } |
| return instance; |
| } |
| |
| public String toString() { |
| return String.format("%s[%s]", creator, SINGLETON); |
| } |
| }; |
| } |
| |
| @Override public String toString() { |
| return "Scopes.SINGLETON"; |
| } |
| }; |
| |
| /** |
| * No scope; the same as not applying any scope at all. Each time the |
| * Injector obtains an instance of an object with "no scope", it injects this |
| * instance then immediately forgets it. When the next request for the same |
| * binding arrives it will need to obtain the instance over again. |
| * |
| * <p>This exists only in case a class has been annotated with a scope |
| * annotation such as {@link Singleton @Singleton}, and you need to override |
| * this to "no scope" in your binding. |
| */ |
| public static final Scope NO_SCOPE = new Scope() { |
| public <T> Provider<T> scope(Key<T> key, Provider<T> unscoped) { |
| return unscoped; |
| } |
| @Override public String toString() { |
| return "Scopes.NO_SCOPE"; |
| } |
| }; |
| |
| /** |
| * Returns the scope annotation on {@code type}, or null if none is specified. |
| */ |
| static Class<? extends Annotation> findScopeAnnotation( |
| Errors errors, Class<?> implementation) { |
| return findScopeAnnotation(errors, implementation.getAnnotations()); |
| } |
| |
| |
| /** |
| * Returns the scoping annotation, or null if there isn't one. |
| */ |
| static Class<? extends Annotation> findScopeAnnotation(Errors errors, Annotation[] annotations) { |
| Class<? extends Annotation> found = null; |
| |
| for (Annotation annotation : annotations) { |
| if (annotation.annotationType() |
| .isAnnotationPresent(ScopeAnnotation.class)) { |
| if (found != null) { |
| errors.duplicateScopeAnnotations(found, annotation.annotationType()); |
| } else { |
| found = annotation.annotationType(); |
| } |
| } |
| } |
| |
| return found; |
| } |
| |
| static boolean isScopeAnnotation(Annotation annotation) { |
| return isScopeAnnotation(annotation.annotationType()); |
| } |
| |
| static boolean isScopeAnnotation(Class<? extends Annotation> annotationType) { |
| return annotationType.isAnnotationPresent(ScopeAnnotation.class); |
| } |
| |
| /** |
| * Scopes an internal factory. |
| */ |
| static <T> InternalFactory<? extends T> scope(Key<T> key, |
| InjectorImpl injector, InternalFactory<? extends T> creator, |
| Scope scope) { |
| // No scope does nothing. |
| if (scope == null || scope == Scopes.NO_SCOPE) { |
| return creator; |
| } |
| Provider<T> scoped = scope.scope(key, |
| new ProviderToInternalFactoryAdapter<T>(injector, creator)); |
| return new InternalFactoryToProviderAdapter<T>(scoped); |
| } |
| } |