org.springframework.webflow.persistence

Class JpaFlowExecutionListener

java.lang.Object

org.springframework.webflow.persistence.JpaFlowExecutionListener

All Implemented Interfaces:

FlowExecutionListener

public class JpaFlowExecutionListener
extends java.lang.Object
implements FlowExecutionListener

A FlowExecutionListener that implements the Flow Managed Persistence Context (FMPC) pattern using the standard Java Persistence API (JPA).

This implementation uses standard JPA APIs. The general pattern is as follows:

• When a flow execution starts, create a new JPA persistence context and bind it to flow scope under the name PERSISTENCE_CONTEXT_ATTRIBUTE.
• Before processing a flow execution request, expose the flow-scoped persistence context as the "current" persistence context for the current thread.
• When an existing flow pauses, unbind the persistence context from the current thread.
• When an existing flow ends, commit the changes made to the persistence context in a transaction if the ending state is a commit state. Then, unbind the context and close it.

The general data access pattern implemented here is:

• Create a new persistence context when a new flow execution with the 'persistenceContext' attribute starts
• Load some objects into this persistence context
• Perform edits to those objects over a series of requests into the flow
• On successful conversation completion, commit and flush those edits to the database, applying a version check if necessary.

Note: All data access except for the final commit will, by default, be non-transactional. However, a flow may call into a transactional service layer to fetch objects during the conversation in the context of a read-only system transaction if the underlying JPA Transaction Manager supports this. Spring's JPA TransactionManager does support this when working with a Hibernate JPA provider, for example. In that case, Spring will handle setting the FlushMode to MANUAL to ensure any in-progress changes to managed persistent entities are not flushed, while reads of new objects occur transactionally.

Care should be taken to prevent premature commits of flow data while the flow is in progress. You would generally not want intermediate flushing to happen, as the nature of a flow implies a transient, isolated resource that can be canceled before it ends. Generally, the only time a read-write transaction should be started is upon successful completion of the flow, triggered by reaching a 'commit' end state.

Author:

Keith Donald, Juergen Hoeller

Field Summary

Fields

Modifier and Type	Field and Description
static java.lang.String	PERSISTENCE_CONTEXT_ATTRIBUTE The name of the attribute the flow persistence context is indexed under.d

Constructor Summary

Constructors

Constructor and Description
JpaFlowExecutionListener(javax.persistence.EntityManagerFactory entityManagerFactory, org.springframework.transaction.PlatformTransactionManager transactionManager) Create a new JPA flow execution listener using given JPA Entity Manager factory.

Method Summary

Modifier and Type	Method and Description
void	exceptionThrown(RequestContext context, FlowExecutionException exception) Called when an exception is thrown during a flow execution, before the exception is handled by any registered handler.
void	paused(RequestContext context) Called when a flow execution is paused, for instance when it is waiting for user input (after event processing).
void	resuming(RequestContext context) Called after a flow execution is successfully reactivated after pause (but before event processing).
void	sessionEnded(RequestContext context, FlowSession session, java.lang.String outcome, AttributeMap<?> output) Called when a flow execution session ends.
void	sessionEnding(RequestContext context, FlowSession session, java.lang.String outcome, MutableAttributeMap<?> output) Called when the active flow execution session has been asked to end but before it has ended.
void	sessionStarting(RequestContext context, FlowSession session, MutableAttributeMap<?> input) Called after a new flow session has been created but before it starts.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface org.springframework.webflow.execution.FlowExecutionListener

eventSignaled, requestProcessed, requestSubmitted, sessionCreating, sessionStarted, stateEntered, stateEntering, transitionExecuting, viewRendered, viewRendering

Field Detail

PERSISTENCE_CONTEXT_ATTRIBUTE

public static final java.lang.String PERSISTENCE_CONTEXT_ATTRIBUTE

The name of the attribute the flow persistence context is indexed under.d

See Also:

Constant Field Values

Constructor Detail

JpaFlowExecutionListener

public JpaFlowExecutionListener(javax.persistence.EntityManagerFactory entityManagerFactory,
                                org.springframework.transaction.PlatformTransactionManager transactionManager)

Create a new JPA flow execution listener using given JPA Entity Manager factory.

Parameters:

entityManagerFactory - the entity manager factory to use

Method Detail

sessionStarting

public void sessionStarting(RequestContext context,
                            FlowSession session,
                            MutableAttributeMap<?> input)

Description copied from interface: FlowExecutionListener

Called after a new flow session has been created but before it starts. Useful for setting arbitrary attributes in the session before the flow starts.

Specified by:

sessionStarting in interface FlowExecutionListener

Parameters:

context - the current flow request context

session - the session that was created

input - a mutable input map - attributes placed in this map are eligible for input mapping by the flow definition at startup

paused

public void paused(RequestContext context)

Description copied from interface: FlowExecutionListener

Called when a flow execution is paused, for instance when it is waiting for user input (after event processing).

Specified by:

paused in interface FlowExecutionListener

Parameters:

context - the current flow request context

resuming

public void resuming(RequestContext context)

Description copied from interface: FlowExecutionListener

Called after a flow execution is successfully reactivated after pause (but before event processing).

Specified by:

resuming in interface FlowExecutionListener

Parameters:

context - the current flow request context

sessionEnding

public void sessionEnding(RequestContext context,
                          FlowSession session,
                          java.lang.String outcome,
                          MutableAttributeMap<?> output)

Description copied from interface: FlowExecutionListener

Called when the active flow execution session has been asked to end but before it has ended.

Specified by:

sessionEnding in interface FlowExecutionListener

Parameters:

context - the current flow request context

session - the current active session that is ending

outcome - the outcome reached by the ending session, generally the id of the terminating end-state

output - the flow output produced by the ending session, this map may be modified by this listener to affect the output returned

sessionEnded

public void sessionEnded(RequestContext context,
                         FlowSession session,
                         java.lang.String outcome,
                         AttributeMap<?> output)

Description copied from interface: FlowExecutionListener

Called when a flow execution session ends. If the ended session was the root session of the flow execution, the entire flow execution also ends.

Specified by:

sessionEnded in interface FlowExecutionListener

Parameters:

context - the current flow request context

session - ending flow session

outcome - the outcome reached by the ended session, generally the id of the terminating end-state

output - the flow output returned by the ending session

exceptionThrown

public void exceptionThrown(RequestContext context,
                            FlowExecutionException exception)

Description copied from interface: FlowExecutionListener

Called when an exception is thrown during a flow execution, before the exception is handled by any registered handler.

Specified by:

exceptionThrown in interface FlowExecutionListener

Parameters:

context - the current flow request context

exception - the exception that occurred