com.google.inject.spi.ProviderWithExtensionVisitor Maven / Gradle / Ivy
/*
* Copyright (C) 2010 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.spi;
import com.google.inject.Binding;
import com.google.inject.Provider;
/**
* A Provider that is part of an extension which supports a custom BindingTargetVisitor.
*
* When an extension binds a provider instance, the provider can implement this interface to
* allow users using the {@link Binding#acceptTargetVisitor(BindingTargetVisitor)} method to visit a
* custom visitor designed for that extension. A typical implementation within the extension would
* look like
*
*
* <V, B> V acceptExtensionVisitor(BindingTargetVisitor<B, V> visitor, ProviderInstanceBinding<? extends B> binding) {
* if(visitor instanceof MyCustomExtensionVisitor) {
* return ((MyCustomExtensionVisitor<B, V>)visitor).visitCustomExtension(customProperties, binding);
* } else {
* return visitor.visit(binding);
* }
* }
*
* 'MyCustomExtensionVisitor' in the example above would be an interface the extension provides that
* users can implement in order to be notified of custom extension information. These visitor
* interfaces must extend from BindingTargetVisitor.
*
* @since 3.0
* @author [email protected] (Sam Berlin)
*/
public interface ProviderWithExtensionVisitor extends Provider {
/**
* Instructs the extension determine if the visitor is an instance of a custom extension visitor,
* and if so, visit it using that method. If the visitor is not an instance of the custom
* extension visitor, this method MUST call visitor.visit(binding).
*
* Due to issues with generics, the type parameters of this method do not relate to the type of
* the provider. In practice, the 'B' type will always be a supertype of 'T'.
*/
V acceptExtensionVisitor(
BindingTargetVisitor visitor, ProviderInstanceBinding binding);
}