This chapter shows how to use Web Flow in a Portlet environment.
Spring Web Flow requires Portlet API 2.0 to run with.
The booking-portlet-mvc sample application is a good reference for using Web Flow within a portlet.
This application is a simplified travel site that allows users to search for and book hotel rooms.
The configuration for a portlet depends on the portlet container used. The sample applications, included with Web Flow, are both configured to use Apache Pluto.
In general, the configuration requires adding a servlet mapping in the web.xml file to dispatch request to the portlet container.
<servlet> <servlet-name>swf-booking-mvc</servlet-name> <servlet-class>org.apache.pluto.core.PortletServlet</servlet-class> <init-param> <param-name>portlet-name</param-name> <param-value>swf-booking-mvc</param-value> </init-param> <load-on-startup>1</load-on-startup> </servlet> <servlet-mapping> <servlet-name>swf-booking-mvc</servlet-name> <url-pattern>/PlutoInvoker/swf-booking-mvc</url-pattern> </servlet-mapping>
The portlet.xml configuration is a standard portlet configuration.
The portlet-class needs to be set along with a pair of init-params.
Setting the expiration-cache to 0 is recommended to force Web Flow to always render a fresh view.
<portlet> ... <portlet-class>org.springframework.web.portlet.DispatcherPortlet</portlet-class> <init-param> <name>contextConfigLocation</name> <value>/WEB-INF/web-application-config.xml</value> </init-param> <init-param> <name>viewRendererUrl</name> <value>/WEB-INF/servlet/view</value> </init-param> <expiration-cache>0</expiration-cache> ... </portlet>
The only supported mechanism for bridging a portlet request to Web Flow is a FlowHandler.
The PortletFlowController used in Web Flow 1.0 is no longer supported.
The flow handler, similar to the servlet flow handler, provides hooks that can:
select the flow to execute
pass input parameters to the flow on initialization
handle the flow execution outcome
handle exceptions
The AbstractFlowHandler class is an implementation of FlowHandler that provides default implementations for these hooks.
In a portlet environment the targeted flow id can not be inferred from the URL and must be defined explicitly in the handler.
public class ViewFlowHandler extends AbstractFlowHandler { public String getFlowId() { return "view"; } }
Spring Portlet MVC provides a rich set of methods to map portlet requests. Complete documentation is available in the Spring Reference Documentation.
The booking-portlet-mvc sample application uses a PortletModeHandlerMapping to map portlet requests.
The sample application only supports view mode, but support for other portlet modes is available.
Other modes can be added and point to the same flow as view mode, or any other flow.
<bean id="portletModeHandlerMapping" class="org.springframework.web.portlet.handler.PortletModeHandlerMapping"> <property name="portletModeMap"> <map> <entry key="view"> <bean class="org.springframework.webflow.samples.booking.ViewFlowHandler" /> </entry> </map> </property> </bean>
A FlowHandlerAdapter converts the handler mappings to the flow handlers.
The flow executor is required as a constructor argument.
<bean id="flowHandlerAdapter" class="org.springframework.webflow.mvc.portlet.FlowHandlerAdapter"> <constructor-arg ref="flowExecutor" /> </bean>
In order to facilitate view rendering, a ViewRendererServlet must be added to the web.xml file.
This servlet is not invoked directly, but it used by Web Flow to render views in a portlet environment.
<servlet> <servlet-name>ViewRendererServlet</servlet-name> <servlet-class>org.springframework.web.servlet.ViewRendererServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>ViewRendererServlet</servlet-name> <url-pattern>/WEB-INF/servlet/view</url-pattern> </servlet-mapping>
The Portlet API defined three window states: normal, minimized and maximized.
The portlet implementation must decide what to render for each of these window states.
Web Flow exposes the string value of the window state under portletWindowState via the request map on the external context.
requestContext.getExternalContext().getRequestMap().get("portletWindowState");
externalContext.requestMap.portletWindowState
The Portlet API defined three portlet modes: view, edit and help.
The portlet implementation must decide what to render for each of these modes.
Web Flow exposes the string value of the portlet mode under portletMode via the request map on the external context.
requestContext.getExternalContext().getRequestMap().get("portletMode");
externalContext.requestMap.portletMode
Prior to version 2.1 of Spring Web Flow, support for JSF Portlets was considered experimental and relied on a Portlet Bridge for JSF implementation. Furthermore JSR-329 (the latest specification in this area), which targets Portlet API 2.0 and JSF 1.2 environments at the time of writing is not yet final causing portlet bridge implementations to also remain incomplete.
A closer comparison of Spring Web Flow and a Portlet Bridge for JSF shows the two have significant overlap. They both drive the JSF lifecycle and they both shield JSF from knowledge about Portlet action and render requests.
Considering all of the above, starting with version 2.2, Spring Web Flow provides support for JSF Portlets using its own internal Portlet integration rather than a Portlet Bridge for JSF. We believe this will provide value for Web Flow users by reducing the number of dependencies in what is already a fairly complex combination of technologies with specifications lagging behind.
What this practically means is the configuration required for JSF Portlets is very similar to what is alread documented in the rest of this chapter with the exception of Section 14.4, “Portlet Views”, which is not necessary with JSF.
Review the swf-booking-portlet-faces sample in the Web Flow distribution
for a working JSF Portlets example with complete configuration details. The main thing
you'll need to notice in addition to what has already been described in this
chapter is the faces-config.xml configuration:
<?xml version="1.0"?> <!DOCTYPE faces-config PUBLIC "-//Sun Microsystems, Inc.//DTD JavaServer Faces Config 1.0//EN" "http://java.sun.com/dtd/web-facesconfig_1_0.dtd"> <faces-config> <application> <view-handler> org.springframework.faces.webflow.application.portlet.PortletFaceletViewHandler </view-handler> </application> </faces-config>
The Portlet API only allows redirects to be requested from an action request.
Because views are rendered on the render request, views and view-states cannot trigger a redirect.
The externalRedirect: view prefix is a convenience for Servlet based flows.
An IllegalStateException is thrown if a redirect is requested from a render request.
end-state redirects can be achieved by implementing FlowHandler.handleExecutionOutcome.
This callback provides the ActionResponse object which supports redirects.
The portlet container passes the execution key from the previous flow when switching to a new mode.
Even if the mode is mapped to a different FlowHandler the flow execution will resume the previous execution.
You may switch the mode programatically in your FlowHandler after ending a flow in an ActionRequest.
One way to start a new flow is to create a URL targeting the mode without the execution key.