org.springframework.webflow.executor.struts
Class FlowAction

java.lang.Object
  org.apache.struts.action.Action
      org.springframework.web.struts.ActionSupport
          org.springframework.webflow.executor.struts.FlowAction

public class FlowAction
extends org.springframework.web.struts.ActionSupport

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 FlowExecutorArgumentHandler.getFlowIdArgumentName() request parameter indicating the flow definition to launch.

To have this controller participate in an existing flow execution (conversation), have the client send a FlowExecutorArgumentHandler.getFlowExecutionKeyArgumentName() 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 maps the logical request URL /userRegistration.do as a Flow controller (FlowAction). 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 dependency injection 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.
• The FlowExecutorArgumentHandler used by the FlowAction can be configured in the root context using a bean of name FLOW_EXECUTOR_ARGUMENT_HANDLER_BEAN_NAME. If not explicitly specified it will default to a normal RequestParameterFlowExecutorArgumentHandler with standard configuration.

The benefits here are considerable: 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.

Author:

Keith Donald, Erwin Vervaet

See Also:

FlowExecutor, FlowRequestHandler, SpringBindingActionForm, DelegatingActionProxy

Field Summary

protected static java.lang.String	FLOW_EXECUTOR_ARGUMENT_HANDLER_BEAN_NAME The flow executor argument handler will be retreived from the application context using this bean name if no argument handler is explicitly set.
protected static java.lang.String	FLOW_EXECUTOR_BEAN_NAME The flow executor will be retreived from the application context using this bean name if no executor is explicitly set.

Fields inherited from class org.apache.struts.action.Action

defaultLocale, servlet

Constructor Summary

FlowAction()

Method Summary

protected org.apache.struts.action.ActionForward	createRedirectForward(java.lang.String url, javax.servlet.http.HttpServletResponse response) Handles a redirect.
protected FlowRequestHandler	createRequestHandler() Factory method that creates a new helper for processing a request into this flow controller.
org.apache.struts.action.ActionForward	execute(org.apache.struts.action.ActionMapping mapping, org.apache.struts.action.ActionForm form, javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response)
protected org.apache.struts.action.ActionForward	findForward(ApplicationView forward, org.apache.struts.action.ActionMapping mapping) Find an action forward for given application view.
FlowExecutorArgumentHandler	getArgumentHandler() Returns the flow executor argument handler used by this controller.
FlowExecutor	getFlowExecutor() Returns the flow executor used by this controller.
protected void	onInit()
void	setArgumentHandler(FlowExecutorArgumentHandler argumentHandler) Sets the flow executor argument handler to use.
void	setFlowExecutor(FlowExecutor flowExecutor) Configures the flow executor implementation to use.
protected org.apache.struts.action.ActionForward	toActionForward(ResponseInstruction responseInstruction, org.apache.struts.action.ActionMapping mapping, org.apache.struts.action.ActionForm form, javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response, ExternalContext context) Return a Struts ActionForward given a ResponseInstruction.

Methods inherited from class org.springframework.web.struts.ActionSupport

getMessageSourceAccessor, getServletContext, getTempDir, getWebApplicationContext, initWebApplicationContext, onDestroy, setServlet

Methods inherited from class org.apache.struts.action.Action

addErrors, addMessages, execute, generateToken, getDataSource, getDataSource, getErrors, getLocale, getMessages, getResources, getResources, getServlet, isCancelled, isTokenValid, isTokenValid, resetToken, saveErrors, saveErrors, saveErrors, saveMessages, saveMessages, saveToken, setLocale

Methods inherited from class java.lang.Object

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

Field Detail

FLOW_EXECUTOR_BEAN_NAME

protected static final java.lang.String FLOW_EXECUTOR_BEAN_NAME

The flow executor will be retreived from the application context using this bean name if no executor is explicitly set. ("flowExecutor")

See Also:

Constant Field Values

FLOW_EXECUTOR_ARGUMENT_HANDLER_BEAN_NAME

protected static final java.lang.String FLOW_EXECUTOR_ARGUMENT_HANDLER_BEAN_NAME

The flow executor argument handler will be retreived from the application context using this bean name if no argument handler is explicitly set. ("argumentHandler")

See Also:

Constant Field Values

Constructor Detail

FlowAction

public FlowAction()

Method Detail

getFlowExecutor

public FlowExecutor getFlowExecutor()

Returns the flow executor used by this controller.

Returns:

the flow executor

setFlowExecutor

public void setFlowExecutor(FlowExecutor flowExecutor)

Configures the flow executor implementation to use. Required.

Parameters:

flowExecutor - the fully configured flow executor

getArgumentHandler

public FlowExecutorArgumentHandler getArgumentHandler()

Returns the flow executor argument handler used by this controller.

Returns:

the argument handler

setArgumentHandler

public void setArgumentHandler(FlowExecutorArgumentHandler argumentHandler)

Sets the flow executor argument handler to use.

Parameters:

argumentHandler - the fully configured argument handler

onInit

protected void onInit()

Overrides:

onInit in class org.springframework.web.struts.ActionSupport

execute

public org.apache.struts.action.ActionForward execute(org.apache.struts.action.ActionMapping mapping,
                                                      org.apache.struts.action.ActionForm form,
                                                      javax.servlet.http.HttpServletRequest request,
                                                      javax.servlet.http.HttpServletResponse response)
                                               throws java.lang.Exception

Overrides:

execute in class org.apache.struts.action.Action

Throws:

java.lang.Exception

createRequestHandler

protected FlowRequestHandler createRequestHandler()

Factory method that creates a new helper for processing a request into this flow controller.

Returns:

the controller helper

toActionForward

protected org.apache.struts.action.ActionForward toActionForward(ResponseInstruction responseInstruction,
                                                                 org.apache.struts.action.ActionMapping mapping,
                                                                 org.apache.struts.action.ActionForm form,
                                                                 javax.servlet.http.HttpServletRequest request,
                                                                 javax.servlet.http.HttpServletResponse response,
                                                                 ExternalContext context)
                                                          throws java.lang.Exception

Return a Struts ActionForward given a ResponseInstruction. Adds all attributes from the ResponseInstruction as request attributes.

Throws:

java.lang.Exception

createRedirectForward

protected org.apache.struts.action.ActionForward createRedirectForward(java.lang.String url,
                                                                       javax.servlet.http.HttpServletResponse response)
                                                                throws java.lang.Exception

Handles a redirect. This implementation simply calls sendRedirect on the response object.

Parameters:

url - the url to redirect to

response - the http response

Returns:

the redirect forward, this implementation returns null

Throws:

java.lang.Exception - an excpetion occured processing the redirect

See Also:

HttpServletResponse.sendRedirect(java.lang.String)

findForward

protected org.apache.struts.action.ActionForward findForward(ApplicationView forward,
                                                             org.apache.struts.action.ActionMapping mapping)

Find an action forward for given application view. If no suitable forward is found in the action mapping using the view name as a key, this method will create a new action forward using the view name.

Parameters:

forward - the application view to find a forward for

mapping - the action mapping to use

Returns:

the action forward, never null