/*
* 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 key (type and optional annotation) 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.
*
* <p>Bindings are created in several ways:
*
* <ul>
* <li>Explicitly in a module, via {@code bind()} and {@code bindConstant()} statements:
* <pre>
* bind(Service.class).annotatedWith(Red.class).to(ServiceImpl.class);
* bindConstant().annotatedWith(ServerHost.class).to(args[0]);</pre>
*
* <li>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.
* <li>By converting a bound instance to a different type.
* <li>For {@link Provider providers}, by delegating to the binding for the provided type.
* </ul>
*
* <p>They exist on both modules and on injectors, and their behaviour is different for each:
*
* <ul>
* <li><strong>Module bindings</strong> 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.
* <li><strong>Injector bindings</strong> 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.
* </ul>
*
* @param <T> the bound type. The injected is always assignable to this type.
* @author crazybob@google.com (Bob Lee)
* @author jessewilson@google.com (Jesse Wilson)
*/
public interface Binding<T> extends Element {
/** Returns the key for this binding. */
Key<T> 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<T> 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> V acceptTargetVisitor(BindingTargetVisitor<? super T, V> 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> V acceptScopingVisitor(BindingScopingVisitor<V> visitor);
}