https://github.com/spring-projects/spring-framework: Spring Beans (Spring IO)
  • Juergen Hoeller 
/*
 * Copyright 2002-2016 the original author or authors.
 *
 * 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
 *
 *      https://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.springframework.beans.factory.config;

import org.springframework.beans.factory.ObjectFactory;
import org.springframework.lang.Nullable;


Strategy interface used by a ConfigurableBeanFactory, representing a target scope to hold bean instances in. This allows for extending the BeanFactory's standard scopes "singleton" and "prototype" with custom further scopes, registered for a specific key. 
ApplicationContext implementations such as a WebApplicationContext may register additional standard scopes specific to their environment, e.g. "request" and "session", based on this Scope SPI. 
Even if its primary use is for extended scopes in a web environment, this SPI is completely generic: It provides the ability to get and put objects from any underlying storage mechanism, such as an HTTP session or a custom conversation mechanism. The name passed into this class's get and remove methods will identify the target object in the current scope. 
Scope implementations are expected to be thread-safe. One Scope instance can be used with multiple bean factories at the same time, if desired (unless it explicitly wants to be aware of the containing BeanFactory), with any number of threads accessing the Scope concurrently from any number of factories. 
Author:Juergen Hoeller, Rob Harrop
See Also:
Since:2.0
/**
 * Strategy interface used by a {@link ConfigurableBeanFactory},
 * representing a target scope to hold bean instances in.
 * This allows for extending the BeanFactory's standard scopes
 * {@link ConfigurableBeanFactory#SCOPE_SINGLETON "singleton"} and
 * {@link ConfigurableBeanFactory#SCOPE_PROTOTYPE "prototype"}
 * with custom further scopes, registered for a
 * {@link ConfigurableBeanFactory#registerScope(String, Scope) specific key}.
 *
 * <p>{@link org.springframework.context.ApplicationContext} implementations
 * such as a {@link org.springframework.web.context.WebApplicationContext}
 * may register additional standard scopes specific to their environment,
 * e.g. {@link org.springframework.web.context.WebApplicationContext#SCOPE_REQUEST "request"}
 * and {@link org.springframework.web.context.WebApplicationContext#SCOPE_SESSION "session"},
 * based on this Scope SPI.
 *
 * <p>Even if its primary use is for extended scopes in a web environment,
 * this SPI is completely generic: It provides the ability to get and put
 * objects from any underlying storage mechanism, such as an HTTP session
 * or a custom conversation mechanism. The name passed into this class's
 * {@code get} and {@code remove} methods will identify the
 * target object in the current scope.
 *
 * <p>{@code Scope} implementations are expected to be thread-safe.
 * One {@code Scope} instance can be used with multiple bean factories
 * at the same time, if desired (unless it explicitly wants to be aware of
 * the containing BeanFactory), with any number of threads accessing
 * the {@code Scope} concurrently from any number of factories.
 *
 * @author Juergen Hoeller
 * @author Rob Harrop
 * @since 2.0
 * @see ConfigurableBeanFactory#registerScope
 * @see CustomScopeConfigurer
 * @see org.springframework.aop.scope.ScopedProxyFactoryBean
 * @see org.springframework.web.context.request.RequestScope
 * @see org.springframework.web.context.request.SessionScope
 */
public interface Scope {

	
Return the object with the given name from the underlying scope, creating it if not found in the underlying storage mechanism. 
This is the central operation of a Scope, and the only operation
that is absolutely required.

Params:
  • name – the name of the object to retrieve
  • objectFactory – the ObjectFactory to use to create the scoped object if it is not present in the underlying storage mechanism
Throws:
Returns:the desired object (never null)
/**
	 * Return the object with the given name from the underlying scope,
	 * {@link org.springframework.beans.factory.ObjectFactory#getObject() creating it}
	 * if not found in the underlying storage mechanism.
	 * <p>This is the central operation of a Scope, and the only operation
	 * that is absolutely required.
	 * @param name the name of the object to retrieve
	 * @param objectFactory the {@link ObjectFactory} to use to create the scoped
	 * object if it is not present in the underlying storage mechanism
	 * @return the desired object (never {@code null})
	 * @throws IllegalStateException if the underlying scope is not currently active
	 */
	Object get(String name, ObjectFactory<?> objectFactory);

	
Remove the object with the given name from the underlying scope. 
Returns null if no object was found; otherwise returns the removed Object. 
Note that an implementation should also remove a registered destruction
callback for the specified object, if any. It does, however, not
need to execute a registered destruction callback in this case,
since the object will be destroyed by the caller (if appropriate).

Note: This is an optional operation. Implementations may throw UnsupportedOperationException if they do not support explicitly removing an object. 
Params:
  • name – the name of the object to remove
Throws:
See Also:
Returns:the removed object, or null if no object was present
/**
	 * Remove the object with the given {@code name} from the underlying scope.
	 * <p>Returns {@code null} if no object was found; otherwise
	 * returns the removed {@code Object}.
	 * <p>Note that an implementation should also remove a registered destruction
	 * callback for the specified object, if any. It does, however, <i>not</i>
	 * need to <i>execute</i> a registered destruction callback in this case,
	 * since the object will be destroyed by the caller (if appropriate).
	 * <p><b>Note: This is an optional operation.</b> Implementations may throw
	 * {@link UnsupportedOperationException} if they do not support explicitly
	 * removing an object.
	 * @param name the name of the object to remove
	 * @return the removed object, or {@code null} if no object was present
	 * @throws IllegalStateException if the underlying scope is not currently active
	 * @see #registerDestructionCallback
	 */
	@Nullable
	Object remove(String name);

	
Register a callback to be executed on destruction of the specified
object in the scope (or at destruction of the entire scope, if the
scope does not destroy individual objects but rather only terminates
in its entirety).

Note: This is an optional operation. This method will only
be called for scoped beans with actual destruction configuration
(DisposableBean, destroy-method, DestructionAwareBeanPostProcessor).
Implementations should do their best to execute a given callback
at the appropriate time. If such a callback is not supported by the
underlying runtime environment at all, the callback must be
ignored and a corresponding warning should be logged.

Note that 'destruction' refers to automatic destruction of the object as part of the scope's own lifecycle, not to the individual scoped object having been explicitly removed by the application. If a scoped object gets removed via this facade's remove(String) method, any registered destruction callback should be removed as well, assuming that the removed object will be reused or manually destroyed. 
Params:
  • name – the name of the object to execute the destruction callback for
  • callback – the destruction callback to be executed.
Note that the passed-in Runnable will never throw an exception,
so it can safely be executed without an enclosing try-catch block.
Furthermore, the Runnable will usually be serializable, provided
that its target object is serializable as well.
Throws:
See Also:
/**
	 * Register a callback to be executed on destruction of the specified
	 * object in the scope (or at destruction of the entire scope, if the
	 * scope does not destroy individual objects but rather only terminates
	 * in its entirety).
	 * <p><b>Note: This is an optional operation.</b> This method will only
	 * be called for scoped beans with actual destruction configuration
	 * (DisposableBean, destroy-method, DestructionAwareBeanPostProcessor).
	 * Implementations should do their best to execute a given callback
	 * at the appropriate time. If such a callback is not supported by the
	 * underlying runtime environment at all, the callback <i>must be
	 * ignored and a corresponding warning should be logged</i>.
	 * <p>Note that 'destruction' refers to automatic destruction of
	 * the object as part of the scope's own lifecycle, not to the individual
	 * scoped object having been explicitly removed by the application.
	 * If a scoped object gets removed via this facade's {@link #remove(String)}
	 * method, any registered destruction callback should be removed as well,
	 * assuming that the removed object will be reused or manually destroyed.
	 * @param name the name of the object to execute the destruction callback for
	 * @param callback the destruction callback to be executed.
	 * Note that the passed-in Runnable will never throw an exception,
	 * so it can safely be executed without an enclosing try-catch block.
	 * Furthermore, the Runnable will usually be serializable, provided
	 * that its target object is serializable as well.
	 * @throws IllegalStateException if the underlying scope is not currently active
	 * @see org.springframework.beans.factory.DisposableBean
	 * @see org.springframework.beans.factory.support.AbstractBeanDefinition#getDestroyMethodName()
	 * @see DestructionAwareBeanPostProcessor
	 */
	void registerDestructionCallback(String name, Runnable callback);

	
Resolve the contextual object for the given key, if any.
E.g. the HttpServletRequest object for key "request".

Params:
  • key – the contextual key
Throws:
Returns:the corresponding object, or null if none found
/**
	 * Resolve the contextual object for the given key, if any.
	 * E.g. the HttpServletRequest object for key "request".
	 * @param key the contextual key
	 * @return the corresponding object, or {@code null} if none found
	 * @throws IllegalStateException if the underlying scope is not currently active
	 */
	@Nullable
	Object resolveContextualObject(String key);

	
Return the conversation ID for the current underlying scope, if any.

The exact meaning of the conversation ID depends on the underlying storage mechanism. In the case of session-scoped objects, the conversation ID would typically be equal to (or derived from) the session ID; in the case of a custom conversation that sits within the overall session, the specific ID for the current conversation would be appropriate. 
Note: This is an optional operation. It is perfectly valid to return null in an implementation of this method if the underlying storage mechanism has no obvious candidate for such an ID. 
Throws:
Returns:the conversation ID, or null if there is no conversation ID for the current scope
/**
	 * Return the <em>conversation ID</em> for the current underlying scope, if any.
	 * <p>The exact meaning of the conversation ID depends on the underlying
	 * storage mechanism. In the case of session-scoped objects, the
	 * conversation ID would typically be equal to (or derived from) the
	 * {@link javax.servlet.http.HttpSession#getId() session ID}; in the
	 * case of a custom conversation that sits within the overall session,
	 * the specific ID for the current conversation would be appropriate.
	 * <p><b>Note: This is an optional operation.</b> It is perfectly valid to
	 * return {@code null} in an implementation of this method if the
	 * underlying storage mechanism has no obvious candidate for such an ID.
	 * @return the conversation ID, or {@code null} if there is no
	 * conversation ID for the current scope
	 * @throws IllegalStateException if the underlying scope is not currently active
	 */
	@Nullable
	String getConversationId();

}