org.elasticsearch.common.inject.Scope Maven / Gradle / Ivy
/*
* 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 org.elasticsearch.common.inject;
/**
* A scope is a level of visibility that instances provided by Guice may have.
* By default, an instance created by the {@link Injector} has no scope,
* meaning it has no state from the framework's perspective -- the
* {@code Injector} creates it, injects it once into the class that required it,
* and then immediately forgets it. Associating a scope with a particular
* binding allows the created instance to be "remembered" and possibly used
* again for other injections.
*
* An example of a scope is {@link Scopes#SINGLETON}.
*
* @author [email protected] (Bob Lee)
*/
public interface Scope {
/**
* Scopes a provider. The returned provider returns objects from this scope.
* If an object does not exist in this scope, the provider can use the given
* unscoped provider to retrieve one.
*
* Scope implementations are strongly encouraged to override
* {@link Object#toString} in the returned provider and include the backing
* provider's {@code toString()} output.
*
* @param key binding key
* @param unscoped locates an instance when one doesn't already exist in this
* scope.
* @return a new provider which only delegates to the given unscoped provider
* when an instance of the requested object doesn't already exist in this
* scope
*/
Provider scope(Key key, Provider unscoped);
/**
* A short but useful description of this scope. For comparison, the standard
* scopes that ship with guice use the descriptions
* {@code "Scopes.SINGLETON"}, {@code "ServletScopes.SESSION"} and
* {@code "ServletScopes.REQUEST"}.
*/
@Override
String toString();
}