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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;

import com.google.inject.internal.CircularDependencyProxy;
import com.google.inject.internal.LinkedBindingImpl;
import com.google.inject.internal.SingletonScope;
import com.google.inject.spi.BindingScopingVisitor;
import com.google.inject.spi.ExposedBinding;

import java.lang.annotation.Annotation;

/**
 * Built-in scope implementations.
 *
 * @author [email protected] (Bob Lee)
 */
public class Scopes {

  private Scopes() {}

  /**
   * One instance per {@link Injector}. Also see {@code @}{@link Singleton}.
   */
  public static final Scope SINGLETON = new SingletonScope();

  /**
   * 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.
   *
   * 

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. * * @since 2.0 */ public static final Scope NO_SCOPE = new Scope() { public Provider scope(Key key, Provider unscoped) { return unscoped; } @Override public String toString() { return "Scopes.NO_SCOPE"; } }; private static final BindingScopingVisitor IS_SINGLETON_VISITOR = new BindingScopingVisitor() { public Boolean visitNoScoping() { return false; } public Boolean visitScopeAnnotation(Class scopeAnnotation) { return scopeAnnotation == Singleton.class || scopeAnnotation == javax.inject.Singleton.class; } public Boolean visitScope(Scope scope) { return scope == Scopes.SINGLETON; } public Boolean visitEagerSingleton() { return true; } }; /** * Returns true if {@code binding} is singleton-scoped. If the binding is a {@link * com.google.inject.spi.LinkedKeyBinding linked key binding} and belongs to an injector (ie. it * was retrieved via {@link Injector#getBinding Injector.getBinding()}), then this method will * also true if the target binding is singleton-scoped. * * @since 3.0 */ public static boolean isSingleton(Binding binding) { do { boolean singleton = binding.acceptScopingVisitor(IS_SINGLETON_VISITOR); if (singleton) { return true; } if (binding instanceof LinkedBindingImpl) { LinkedBindingImpl linkedBinding = (LinkedBindingImpl) binding; Injector injector = linkedBinding.getInjector(); if (injector != null) { binding = injector.getBinding(linkedBinding.getLinkedKey()); continue; } } else if(binding instanceof ExposedBinding) { ExposedBinding exposedBinding = (ExposedBinding)binding; Injector injector = exposedBinding.getPrivateElements().getInjector(); if (injector != null) { binding = injector.getBinding(exposedBinding.getKey()); continue; } } return false; } while (true); } /** * Returns true if {@code binding} has the given scope. If the binding is a {@link * com.google.inject.spi.LinkedKeyBinding linked key binding} and belongs to an injector (ie. it * was retrieved via {@link Injector#getBinding Injector.getBinding()}), then this method will * also true if the target binding has the given scope. * * @param binding binding to check * @param scope scope implementation instance * @param scopeAnnotation scope annotation class * @since 4.0 */ public static boolean isScoped(Binding binding, final Scope scope, final Class scopeAnnotation) { do { boolean matches = binding.acceptScopingVisitor(new BindingScopingVisitor() { public Boolean visitNoScoping() { return false; } public Boolean visitScopeAnnotation(Class visitedAnnotation) { return visitedAnnotation == scopeAnnotation; } public Boolean visitScope(Scope visitedScope) { return visitedScope == scope; } public Boolean visitEagerSingleton() { return false; } }); if (matches) { return true; } if (binding instanceof LinkedBindingImpl) { LinkedBindingImpl linkedBinding = (LinkedBindingImpl) binding; Injector injector = linkedBinding.getInjector(); if (injector != null) { binding = injector.getBinding(linkedBinding.getLinkedKey()); continue; } } else if(binding instanceof ExposedBinding) { ExposedBinding exposedBinding = (ExposedBinding)binding; Injector injector = exposedBinding.getPrivateElements().getInjector(); if (injector != null) { binding = injector.getBinding(exposedBinding.getKey()); continue; } } return false; } while (true); } /** * Returns true if the object is a proxy for a circular dependency, * constructed by Guice because it encountered a circular dependency. Scope * implementations should be careful to not cache circular proxies, * because the proxies are not intended for general purpose use. (They are * designed just to fulfill the immediate injection, not all injections. * Caching them can lead to IllegalArgumentExceptions or ClassCastExceptions.) * * @since 4.0 */ public static boolean isCircularProxy(Object object) { return object instanceof CircularDependencyProxy; } }





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