org.springframework.webflow.execution.repository.continuation
Class ClientContinuationFlowExecutionRepository

java.lang.Object
  org.springframework.webflow.execution.repository.support.AbstractFlowExecutionRepository
      org.springframework.webflow.execution.repository.support.AbstractConversationFlowExecutionRepository
          org.springframework.webflow.execution.repository.continuation.ClientContinuationFlowExecutionRepository

All Implemented Interfaces:

FlowExecutionRepository

public class ClientContinuationFlowExecutionRepository
extends AbstractConversationFlowExecutionRepository

Stores flow execution state client side, requiring no use of server-side state.

More specifically, instead of putting FlowExecution objects in a server-side store this repository encodes them directly into the continuationId of the generated FlowExecutionKey. When asked to load a flow execution by its key this repository decodes the serialized continuationId, restoring the FlowExecution object at the state it was in when encoded.

Note: currently this repository implementation does not by default support conversation management. This has two consequences. First, there is no conversation invalidation after completion, which enables automatic prevention of duplicate submission after a conversation has completed. Secondly, The contents of conversation scope will not be maintained across requests. Support for these features requires tracking active conversations using a conversation service backed by some centralized storage medium like a database table. If you want to have proper conversation management, configure this class with an appropriate conversation manager (the default conversation manager used does nothing).

Warning: storing state (a flow execution continuation) on the client entails a certain security risk. This implementation does not provide a secure way of storing state on the client, so a malicious client could reverse engineer a continuation and get access to possible sensitive data stored in the flow execution. If you need more security and still want to store continuations on the client, subclass this class and override the methods encode(FlowExecution) and decode(String), implementing them with a secure encoding/decoding algorithm, e.g. based on public/private key encryption.

This class depends on the Jakarta Commons Codec library to do BASE64 encoding. Codec code must be available in the classpath when using this implementation.

Author:

Keith Donald, Erwin Vervaet

See Also:

Base64

Constructor Summary

ClientContinuationFlowExecutionRepository(FlowExecutionStateRestorer executionStateRestorer)
Creates a new client continuation repository.

ClientContinuationFlowExecutionRepository(FlowExecutionStateRestorer executionStateRestorer, ConversationManager conversationManager)
Creates a new client continuation repository.

Method Summary

protected FlowExecutionContinuation	decode(java.lang.String encodedContinuation) Decode given data, received from the client, and return the corresponding flow execution object.
protected java.io.Serializable	encode(FlowExecution flowExecution) Encode given flow execution object into data that can be stored on the client.
protected java.io.Serializable	generateContinuationId(FlowExecution flowExecution) Template method used to generate a new continuation id for given flow execution.
protected FlowExecutionContinuationFactory	getContinuationFactory() Returns the continuation factory in use by this repository.
FlowExecution	getFlowExecution(FlowExecutionKey key) Return the FlowExecution indexed by the provided key.
protected java.io.Serializable	parseContinuationId(java.lang.String encodedId) Template method to parse the continuation id from the encoded string.
void	putFlowExecution(FlowExecutionKey key, FlowExecution flowExecution) Place the FlowExecution in this repository under the provided key.
void	setContinuationFactory(FlowExecutionContinuationFactory continuationFactory) Sets the continuation factory used by this repository.

Methods inherited from class org.springframework.webflow.execution.repository.support.AbstractConversationFlowExecutionRepository

createConversationParameters, generateKey, getContinuationId, getConversation, getConversationId, getConversationManager, getConversationScope, getLock, getNextKey, onBegin, onEnd, parseFlowExecutionKey, putConversationScope, removeFlowExecution

Methods inherited from class org.springframework.webflow.execution.repository.support.AbstractFlowExecutionRepository

getExecutionStateRestorer

Methods inherited from class java.lang.Object

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

Constructor Detail

ClientContinuationFlowExecutionRepository

public ClientContinuationFlowExecutionRepository(FlowExecutionStateRestorer executionStateRestorer)

Creates a new client continuation repository. Uses a 'no op' conversation manager by default.

Parameters:

executionStateRestorer - the transient flow execution state restorer

ClientContinuationFlowExecutionRepository

public ClientContinuationFlowExecutionRepository(FlowExecutionStateRestorer executionStateRestorer,
                                                 ConversationManager conversationManager)

Creates a new client continuation repository. Use this contructor when you want to use a particular conversation manager, e.g. one that does proper conversation management.

Parameters:

executionStateRestorer - the transient flow execution state restorer

conversationManager - the conversation manager for managing centralized conversational state

Method Detail

getContinuationFactory

protected FlowExecutionContinuationFactory getContinuationFactory()

Returns the continuation factory in use by this repository.

setContinuationFactory

public void setContinuationFactory(FlowExecutionContinuationFactory continuationFactory)

Sets the continuation factory used by this repository.

getFlowExecution

public FlowExecution getFlowExecution(FlowExecutionKey key)

Description copied from interface: FlowExecutionRepository

Return the FlowExecution indexed by the provided key. The returned flow execution represents the restored state of an executing flow from a point in time. This should be called to resume a persistent flow execution.

Specified by:

getFlowExecution in interface FlowExecutionRepository

Specified by:

getFlowExecution in class AbstractConversationFlowExecutionRepository

Parameters:

key - the flow execution key

Returns:

the flow execution, fully hydrated and ready to signal an event against

putFlowExecution

public void putFlowExecution(FlowExecutionKey key,
                             FlowExecution flowExecution)

Description copied from interface: FlowExecutionRepository

Place the FlowExecution in this repository under the provided key. This should be called to save or update the persistent state of an active (but paused) flow execution.

Specified by:

putFlowExecution in interface FlowExecutionRepository

Specified by:

putFlowExecution in class AbstractConversationFlowExecutionRepository

Parameters:

key - the flow execution key

flowExecution - the flow execution

generateContinuationId

protected final java.io.Serializable generateContinuationId(FlowExecution flowExecution)

Description copied from class: AbstractConversationFlowExecutionRepository

Template method used to generate a new continuation id for given flow execution. Subclasses must override.

Specified by:

generateContinuationId in class AbstractConversationFlowExecutionRepository

Parameters:

flowExecution - the flow execution

Returns:

the continuation id

parseContinuationId

protected final java.io.Serializable parseContinuationId(java.lang.String encodedId)

Description copied from class: AbstractConversationFlowExecutionRepository

Template method to parse the continuation id from the encoded string.

Specified by:

parseContinuationId in class AbstractConversationFlowExecutionRepository

Parameters:

encodedId - the string identifier

Returns:

the parsed continuation id

encode

protected java.io.Serializable encode(FlowExecution flowExecution)

Encode given flow execution object into data that can be stored on the client.

Subclasses can override this to change the encoding algorithm. This class just does a BASE64 encoding of the serialized flow execution.

Parameters:

flowExecution - the flow execution instance

Returns:

the encoded representation

decode

protected FlowExecutionContinuation decode(java.lang.String encodedContinuation)

Decode given data, received from the client, and return the corresponding flow execution object.

Subclasses can override this to change the decoding algorithm. This class just does a BASE64 decoding and then deserializes the flow execution.

Parameters:

encodedContinuation - the encoded flow execution data

Returns:

the decoded flow execution instance