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/*
 * Copyright (C) 2008 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.spi.BindingScopingVisitor;
import com.google.inject.spi.BindingTargetVisitor;
import com.google.inject.spi.Element;

/**
 * A mapping from a {@link Key} to the strategy for getting instances of the type. This interface is
 * part of the introspection API and is intended primarily for use by tools.
 *
 * 

Bindings are created in several ways: * *

    *
  • Explicitly in a module, via {@code bind()} and {@code bindConstant()} statements: *
     *     bind(Service.class).annotatedWith(Red.class).to(ServiceImpl.class);
     *     bindConstant().annotatedWith(ServerHost.class).to(args[0]);
    *
  • Implicitly by the Injector by following a type's {@link ImplementedBy pointer} {@link * ProvidedBy annotations} or by using its {@link Inject annotated} or default constructor. *
  • By converting a bound instance to a different type. *
  • For {@link Provider providers}, by delegating to the binding for the provided type. *
* *

They exist on both modules and on injectors, and their behaviour is different for each: * *

    *
  • Module bindings are incomplete and cannot be used to provide instances. * This is because the applicable scopes and interceptors may not be known until an injector * is created. From a tool's perspective, module bindings are like the injector's source code. * They can be inspected or rewritten, but this analysis must be done statically. *
  • Injector bindings are complete and valid and can be used to provide * instances. From a tools' perspective, injector bindings are like reflection for an * injector. They have full runtime information, including the complete graph of injections * necessary to satisfy a binding. *
* * @param the bound type. The injected is always assignable to this type. * @author [email protected] (Bob Lee) * @author [email protected] (Jesse Wilson) */ public interface Binding extends Element { /** Returns the key for this binding. */ Key getKey(); /** * Returns the scoped provider guice uses to fulfill requests for this binding. * * @throws UnsupportedOperationException when invoked on a {@link Binding} created via {@link * com.google.inject.spi.Elements#getElements}. This method is only supported on {@link * Binding}s returned from an injector. */ Provider getProvider(); /** * Accepts a target visitor. Invokes the visitor method specific to this binding's target. * * @param visitor to call back on * @since 2.0 */ V acceptTargetVisitor(BindingTargetVisitor visitor); /** * Accepts a scoping visitor. Invokes the visitor method specific to this binding's scoping. * * @param visitor to call back on * @since 2.0 */ V acceptScopingVisitor(BindingScopingVisitor visitor); }




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