Spring Webflow Plugin

Name	Spring Webflow Plugin
Publisher	Tom Schneider
License	Open Source (ASL2)
Version	1.0.3 Production
Compatibility	Struts 2.0.6+
Homepage	http://code.google.com/p/struts2webflow/
Download	http://code.google.com/p/struts2webflow/downloads/list

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Overview

The Spring Webflow plugin integrates Spring Webflow (SWF) with Struts 2. It allows Struts 2 to execute spring webflows and allows spring webflows to have Struts 2 actions as webflow actions. There is also a sample car insurance app that illustrates usage of the plugin.

Features

Allows Struts 2 to execute spring webflows
Allows Struts 2 actions to be invoked by spring webflow.
Includes an interceptor that injects flow scope properties into Struts 2 actions.
Includes an annotation-based interceptor that injects flow scope properties into Struts 2 actions.
SWF flow execution key can be managed in the session rather than as a hidden field on the client.

Requirements

Spring 2.0+
Spring Webflow 1.0+
Struts 2.0.6+
Struts2Webflow 1.0.3+

Installation

See http://code.google.com/p/struts2plugin-maven-repo/ if you use maven.

For non-maven users, this plugin can be installed by copying the plugin jar into your application's /WEB-INF/lib directory.

Getting Started

Prerequisite

For background information on the core Spring Webflow concepts, visit http://www.ervacon.com/products/swf/intro/.

Step 1 - Create your flow definition xml

<?xml version="1.0" encoding="UTF-8"?>
<flow xmlns="http://www.springframework.org/schema/webflow"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:schemaLocation="http://www.springframework.org/schema/webflow
                          http://www.springframework.org/schema/webflow/spring-webflow-1.0.xsd">

	<start-state idref="ageEnter" />

	<view-state id="ageEnter" view="ageEnter">
		<transition on="submit" to="AgeSave" />
	</view-state>

	<view-state id="ageEnterJSP" view="ageEnter">
		<transition on="input" to="enterAgeJSP" />
		<transition on="submit" to="AgeSave" />
	</view-state>

	<action-state id="AgeSave">
		<action bean="struts2FlowAdapter"/>
		<transition on="input" to="enterAgeJSP" />
		<transition on="success" to="calcRate" />
	</action-state>

	<view-state id="calcRate" view="calcRate">
		<transition on="finish" to="finish" />
	</view-state>

	<end-state id="finish" view="finish"/>
</flow>

Step 2 - Configure Spring's applicationContext.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:flow="http://www.springframework.org/schema/webflow-config"
       xsi:schemaLocation="
           http://www.springframework.org/schema/beans
           http://www.springframework.org/schema/beans/spring-beans-2.0.xsd
           http://www.springframework.org/schema/webflow-config
           http://www.springframework.org/schema/webflow-config/spring-webflow-config-1.0.xsd">

	<!-- Launches new flow executions and resumes existing executions. -->	
	<flow:executor id="flowExecutor" registry-ref="flowRegistry">
		<flow:execution-attributes>
		  <flow:alwaysRedirectOnPause value="false"/>
		</flow:execution-attributes>
	</flow:executor>
	
	<!-- Creates the registry of flow definitions for this application -->
	<flow:registry id="flowRegistry">
		<flow:location path="/WEB-INF/flows/**-flow.xml"/>
	</flow:registry>
	
	<bean id="struts2FlowAdapter" class="com.googlecode.struts2webflow.Struts2FlowAdapter"></bean>
</beans>

The Struts2FlowAdapter allows a Struts 2 action to execute a webflow action-state. The Struts2FlowAdapter uses the id of the action state as the name of Struts 2 action to execute. The alwaysRedirectOnPause is disabled because whether to redirect or not is easier to control in the Struts 2 configuration files.

Step 3 - Add SWF interceptors to Struts's struts.xml configuration file

<interceptors>
	<interceptor name="sessionFlowExecKey" class="com.googlecode.struts2webflow.SessionFlowExecKeyInterceptor"/>
	<interceptor name="annotationflowScope" class="com.googlecode.struts2webflow.annotations.AnnotationFlowScopeInterceptor"/>
</interceptors>

The SessionFlowExecKeyInterceptor puts the flow execution key in the session rather than having it as a hidden field on the form that submitted back. The AnnotationFlowScopeInterceptor uses annotations to bind Struts 2 action variables to and from flow scope. Before an action executes, this interceptor looks for @FlowIn annotated properties of the Struts 2 action and populates the these actions from flow scope. After the action has executed, properties annotated with the @FlowOut annotation are put back into flow scope.

Step 4 - Configure the FlowAction so Spring Webflows can be executed

<action name="FlowAction" class="com.googlecode.struts2webflow.FlowAction">
	<interceptor-ref name="sessionFlowExecKey" />
	<interceptor-ref name="defaultStack" />
	<param name="flowId">rating-flow</param>
	<result name="ageEnter" type="redirect">
		AgeEnter.action
	</result>
	<result name="ageEnterJSP">/example/enterage.jsp</result>
	<result name="calcRate" type="redirect">
		CalcRate.action
	</result>
	<result name="finish">/example/finished.jsp</result>
</action>

For each view-state defined in the flow xml definition, there should be a corresponding result entry in the FlowAction definition. (Or a global result for that view-state)

Step 5 - Access the flow

The flow can now be launched by accessing the FlowAction.

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