going back a state

[totoliso]

Hi, I have the following flow:

State 1--->State 2
| |
----<--------
(back)

But when i take the back transition i have an error.

The question is :
Can i make my flows go backward or always forward?
The back event is trigger by
<a href = "flowController.html?_flowExecutionKey = ${flowExecutionKey}&_eventId=backr">Back</a>

What is the problem?

Thanks!!

<start-state idref="listarUnidades" />

  <view-state id="listarUnidades" view="seleccionarUnidad">
	    <render-actions>
				<bean-action bean="unidadFacade" method="findUnidadesAdministrativas">
					<method-result name="unidades"/>
				</bean-action>
		    </render-actions>
			<transition on="select" to="listarExpedientes">
				<set attribute="idUnidad" scope="flow" value="${requestParameters.idUnidad}"/>
			</transition>
		</view-state>
		
		<view-state id="listarExpedientes" view="listarExpedientes">
			<render-actions>
				<bean-action bean="expedienteFacade" method="findExpedientesByUnidad">
					<method-arguments>
						<argument expression = "${flowScope.idUnidad}" parameter-type="long"/>
					</method-arguments>
					<method-result name="expedientes"/>
				</bean-action>
			</render-actions>
			<transition on="select" to="verExpediente"/>
			<transition on="back" to="listarUnidades"/>
		</view-state>

And get the error when taking the back transition:

org.springframework.web.util.NestedServletException: Request processing failed; nested exception is org.springframework.webflow.executor.support.FlowExecutorArgumentExtractionException: Unable to extract the flow definition id parameter: make sure the client provides the '_flowId' parameter as input or set the 'defaultFlowId' property; the parameters provided in this request are: map['_flowExecutionKey ' -> ' _cC3592784-3986-BA51-1DAE-21C871F31FEF_kE192128A-9D46-E2C6-1B86-07EB72B912A1', '_eventId' -> 'volver']
	org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:411)
	org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:354)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:689)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:802)

causa raíz

org.springframework.webflow.executor.support.FlowExecutorArgumentExtractionException: Unable to extract the flow definition id parameter: make sure the client provides the '_flowId' parameter as input or set the 'defaultFlowId' property; the parameters provided in this request are: map['_flowExecutionKey ' -> ' _cC3592784-3986-BA51-1DAE-21C871F31FEF_kE192128A-9D46-E2C6-1B86-07EB72B912A1', '_eventId' -> 'volver']
	org.springframework.webflow.executor.support.RequestParameterFlowExecutorArgumentHandler.extractFlowId(RequestParameterFlowExecutorArgumentHandler.java:81)
	org.springframework.webflow.executor.support.FlowRequestHandler.handleFlowRequest(FlowRequestHandler.java:130)
	org.springframework.webflow.executor.mvc.FlowController.handleRequestInternal(FlowController.java:172)
	org.springframework.web.servlet.mvc.AbstractController.handleRequest(AbstractController.java:153)
	org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter.handle(SimpleControllerHandlerAdapter.java:48)
	org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:819)
	org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:754)
	org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:399)
	org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:354)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:689)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:802)

[totoliso]

I make it work adding the _flowId parameter in the link
<a href = "flowController.html?_flowExecutionKey = ${flowExecutionKey}&_eventId=back"&_flowId=selecci onarUnidad-flow>Back</a>

But i don't understand it is necessary here and why it is not necessary if the transition is to a forward state.

By!

[totoliso]

Hi, i come with the problem again:
When the transition is to ingresar, it works ok, but from then ,
it has the same error asking for the _flowId.

What is the problem? The flow is the same, i'm not leaving it.
Do i miss something???

<?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="listarUnidades" />

	<view-state id="listarUnidades" view="listarUnidades">
		<render-actions>
			<bean-action bean = "unidadFacade" method = "findUnidadesAdministrativas">
				<method-result name = "unidades"/>
			</bean-action>
		</render-actions>
		<transition on = "select" to = "ingreso">
			<set attribute = "idUnidad" scope = "flow" value = "${requestParameters.idUnidad}"/>
		</transition>
	</view-state>
			
	<view-state id="ingreso" view="ingreso">
	 	<transition on = "entrada"  to = "listarExpedientesEnUnidad" />
		<transition on = "recibir"  to = "listarExpedientesARecibir" />
		<transition on = "cancelar" to = "listarExpedientesACancelar" />
	</view-state>
	
	<subflow-state id = "listarExpedientesEnUnidad" flow = "listarExpedientesEnUnidad-flow">
		<attribute-mapper>
			<input-mapper>
				<mapping source = "${requestParameters.idUnidad}" target = "idUnidad" from = "string" to = "long"/> 
			</input-mapper>
		</attribute-mapper>
		<transition on = "finish" to = "ingreso"/>
	</subflow-state>
		
</flow>

[totoliso]

The problem was the jps link:

<a href = "flowController.html?_flowExecutionKey = ${flowExecutionKey}&_eventId = volver">Unidades administrativas</a>

the correct form is without the spaces:

<a href = "flowController.html?_flowExecutionKey=${flowExecu tionKey}&_eventId=volver">Unidades administrativas</a>

[ravkrr]

Hello there,

even though what you are doing is good. I suggest you find a way to store get the previousStateId, by storing it in the flowscope. You can use the listeners to that. If you get bigger flows I think this would be better. I would appreciate an opinion from the senior members on this if possible.

regards
Kris