org.springframework.beans.factory.config
Interface Scope

All Known Implementing Classes:
AbstractRequestAttributesScope, RequestScope, SessionScope, SimpleThreadScope

public interface Scope

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.

Since:
2.0
Author:
Juergen Hoeller, Rob Harrop
See Also:
ConfigurableBeanFactory.registerScope(java.lang.String, org.springframework.beans.factory.config.Scope), CustomScopeConfigurer, ScopedProxyFactoryBean, RequestScope, SessionScope

Method Summary
 java.lang.Object get(java.lang.String name, ObjectFactory<?> objectFactory)
          Return the object with the given name from the underlying scope, creating it if not found in the underlying storage mechanism.
 java.lang.String getConversationId()
          Return the conversation ID for the current underlying scope, if any.
 void registerDestructionCallback(java.lang.String name, java.lang.Runnable callback)
          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).
 java.lang.Object remove(java.lang.String name)
          Remove the object with the given name from the underlying scope.
 java.lang.Object resolveContextualObject(java.lang.String key)
          Resolve the contextual object for the given key, if any.
 

Method Detail

get

java.lang.Object get(java.lang.String name,
                     ObjectFactory<?> objectFactory)
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.

Parameters:
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
Returns:
the desired object (never null)

remove

java.lang.Object remove(java.lang.String name)
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.

Parameters:
name - the name of the object to remove
Returns:
the removed object, or null if no object was present
See Also:
registerDestructionCallback(java.lang.String, java.lang.Runnable)

registerDestructionCallback

void registerDestructionCallback(java.lang.String name,
                                 java.lang.Runnable callback)
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 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.

Parameters:
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.
See Also:
DisposableBean, AbstractBeanDefinition.getDestroyMethodName(), DestructionAwareBeanPostProcessor

resolveContextualObject

java.lang.Object resolveContextualObject(java.lang.String key)
Resolve the contextual object for the given key, if any. E.g. the HttpServletRequest object for key "request".

Parameters:
key - the contextual key
Returns:
the corresponding object, or null if none found

getConversationId

java.lang.String getConversationId()
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.

Returns:
the conversation ID, or null if there is no conversation ID for the current scope