FlowAction Spring Webflow 1.0.rc2 API Documentation and Javadoc

Library:	Spring Webflow 1.0.rc2
Package:	org.springframework.webflow.executor.struts

Class

public class FlowAction
extends ActionSupport

Overview

Inheritance

Members

Usage

Source

Books

SinceNot specified.

VersionNot specified.

Author(s)Keith Donald, Erwin Vervaet

Point of integration between Struts and Spring Web Flow: a Struts Action that acts a front controller entry point into the web flow system. A single FlowAction may launch any new FlowExecution. In addition, a single Flow Action may signal events in any existing/restored FlowExecutions.

Requests are managed by and delegated to a FlowExecutor , which this class delegates to using a FlowRequestHandler (allowing reuse of common front flow controller logic in other environments). Consult the JavaDoc of those classes for more information on how requests are processed.

By default, to have this controller launch a new flow execution (conversation), have the client send a getFlowIdParameterName() request parameter indicating the flow definition to launch.

To have this controller participate in an existing flow execution (conversation), have the client send a getFlowExecutionKeyParameterName() request parameter identifying the conversation to participate in.

On each request received by this action, a StrutsExternalContext object is created as input to the web flow system. This external source event provides access to the action form, action mapping, and other struts-specific constructs.

This class also is aware of the SpringBindingActionForm adapter, which adapts Spring's data binding infrastructure (based on POJO binding, a standard Errors interface, and property editor type conversion) to the Struts action form model. This option gives backend web-tier developers full support for POJO-based binding with minimal hassel, while still providing consistency to view developers who already have a lot of experience with Struts for markup and request dispatching.

Below is an example struts-config.xml configuration for a FlowAction:

     <action path="/userRegistration"
         type="org.springframework.webflow.executor.struts.FlowAction"
         name="springBindingActionForm" scope="request">
     </action>

This example associates the logical request URL /userRegistration.do as a Flow controller. It is expected that flows to launch be provided in a dynamic fashion by the views (allowing this single FlowAction to manage any number of flow executions). A Spring binding action form instance is set in request scope, acting as an adapter enabling POJO-based binding and validation with Spring.

Other notes regarding Struts/Spring Web Flow integration:

Logical view names returned when ViewStates and EndStates are entered are mapped to physical view templates using standard Struts action forwards (typically global forwards).
Use of the SpringBindingActionForm requires no special setup in struts-config.xml: simply declare a form bean in request scope of the class org.springframework.web.struts.SpringBindingActionForm and use it with your FlowAction.
This class depends on a FlowExecutor instance to be configured.
If relying on Spring's DelegatingActionProxy (which is recommended), a FlowExecutor reference can simply be injected using standard Spring DependencyInjection techniques. If you are not using the proxy-based approach, this class will attempt a root context lookup on initialization, first querying for a bean of instance FlowExecutor named FLOW_EXECUTOR_BEAN_NAME , then, if not found, querying for a bean of instance FlowLocator named FLOW_LOCATOR_BEAN_NAME . If the FlowLocator dependency is resolved, this class will automatically configure a default flow executor implementation suitable for a Struts environment (see setFlowLocator(FlowLocator) ). In addition, you may choose to simply inject a FlowLocator directly if the FlowExecutor defaults meet your requirements.

The benefits here are substantial: developers now have a powerful web flow capability integrated with Struts, with a consistent-approach to POJO-based binding and validation that addresses the proliferation of ActionForm classes found in traditional Struts-based apps.