https://github.com/google/guice/guice: Guice is a lightweight dependency injection framework for Java 6 and above (Google, Inc.) 
/*
 * 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;


A scope is a level of visibility that instances provided by Guice may have. By default, an instance created by the Injector has no scope, meaning it has no state from the framework's perspective -- the 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 Scopes.SINGLETON. 
Author:crazybob@google.com (Bob Lee)
/**
 * A scope is a level of visibility that instances provided by Guice may have. By default, an
 * instance created by the {@link Injector} has <i>no scope</i>, 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.
 *
 * <p>An example of a scope is {@link Scopes#SINGLETON}.
 *
 * @author crazybob@google.com (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 Object.toString in the returned provider and include the backing provider's toString() output. 
Params:
  • key – binding key
  • unscoped – locates an instance when one doesn't already exist in this scope.
Returns: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
/**
   * 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.
   *
   * <p>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
   */
  public <T> Provider<T> scope(Key<T> key, Provider<T> unscoped);

  
A short but useful description of this scope. For comparison, the standard scopes that ship with guice use the descriptions "Scopes.SINGLETON", "ServletScopes.SESSION" and "ServletScopes.REQUEST". 
/**
   * 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();
}