Spring Web Flow provides a JSF integration that lets you use the JSF UI Component Model with Spring Web Flow controllers. Web Flow also provides a Spring Security tag library for use in JSF environments, see Section 13.9, “Using the Spring Security Facelets Tag Library” for more details.
Spring Web Flow 2.5 requires JSF 2.2 or higher.
The first step is to route requests to the
DispatcherServlet in the web.xml file. In this
example, we map all URLs that begin with /spring/ to the
servlet. The servlet needs to be configured. An init-param is
used in the servlet to pass the contextConfigLocation. This
is the location of the Spring configuration for your web
application.
<servlet> <servlet-name>Spring MVC Dispatcher Servlet</servlet-name> <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class> <init-param> <param-name>contextConfigLocation</param-name> <param-value>/WEB-INF/web-application-config.xml</param-value> </init-param> <load-on-startup>1</load-on-startup> </servlet> <servlet-mapping> <servlet-name>Spring MVC Dispatcher Servlet</servlet-name> <url-pattern>/spring/*</url-pattern> </servlet-mapping>
In order for JSF to bootstrap correctly, the
FacesServlet must be configured in web.xml as it
normally would even though you generally will not need to route requests
through it at all when using JSF with Spring Web Flow.
<!-- Just here so the JSF implementation can initialize, *not* used at runtime --> <servlet> <servlet-name>Faces Servlet</servlet-name> <servlet-class>javax.faces.webapp.FacesServlet</servlet-class> <load-on-startup>1</load-on-startup> </servlet> <!-- Just here so the JSF implementation can initialize --> <servlet-mapping> <servlet-name>Faces Servlet</servlet-name> <url-pattern>*.faces</url-pattern> </servlet-mapping>
The use of Facelets instead of JSP typically requires this in web.xml:
!-- Use JSF view templates saved as *.xhtml, for use with Facelets --> <context-param> <param-name>javax.faces.DEFAULT_SUFFIX</param-name> <param-value>.xhtml</param-value> </context-param>
This section explains how to configure Web Flow with JSF. Both Java and XML style configuration are supported. The following is sample configuration for Web Flow and JSF in 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:webflow="http://www.springframework.org/schema/webflow-config" xmlns:faces="http://www.springframework.org/schema/faces" si:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/webflow-config http://www.springframework.org/schema/webflow-config/spring-webflow-config.xsd http://www.springframework.org/schema/faces http://www.springframework.org/schema/faces/spring-faces.xsd"> <!-- Executes flows: the central entry point into the Spring Web Flow system --> <webflow:flow-executor id="flowExecutor"> <webflow:flow-execution-listeners> <webflow:listener ref="facesContextListener"/> </webflow:flow-execution-listeners> </webflow:flow-executor> <!-- The registry of executable flow definitions --> <webflow:flow-registry id="flowRegistry" flow-builder-services="flowBuilderServices" base-path="/WEB-INF"> <webflow:flow-location-pattern value="**/*-flow.xml" /> </webflow:flow-registry> <!-- Configures the Spring Web Flow JSF integration --> <faces:flow-builder-services id="flowBuilderServices" /> <!-- A listener maintain one FacesContext instance per Web Flow request. --> <bean id="facesContextListener" class="org.springframework.faces.webflow.FlowFacesContextLifecycleListener" /> </beans>
The following is an example of the same in Java configuration:
import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; import org.springframework.faces.config.*; @Configuration public class WebFlowConfig extends AbstractFacesFlowConfiguration { @Bean public FlowExecutor flowExecutor() { return getFlowExecutorBuilder(flowRegistry()) .addFlowExecutionListener(new FlowFacesContextLifecycleListener()) .build(); } @Bean public FlowDefinitionRegistry flowRegistry() { return getFlowDefinitionRegistryBuilder() .setBasePath("/WEB-INF") .addFlowLocationPattern("**/*-flow.xml").build(); }
The main points are the installation of a
FlowFacesContextLifecycleListener that manages a single
FacesContext for the duration of Web Flow request and the use of the
flow-builder-services element from the faces
custom namespace to configure rendering for a JSF environment.
In a JSF environment you'll also need this Spring MVC related configuration:
<?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:faces="http://www.springframework.org/schema/faces" xsi:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/faces http://www.springframework.org/schema/faces/spring-faces.xsd"> <faces:resources /> <bean class="org.springframework.faces.webflow.JsfFlowHandlerAdapter"> <property name="flowExecutor" ref="flowExecutor" /> </bean> </beans>
The resources custom namespace element delegates JSF
resource requests to the JSF resource API. The
JsfFlowHandlerAdapter is a replacement for the
FlowHandlerAdapter normally used with Web Flow. This adapter
initializes itself with a JsfAjaxHandler instead of the
SpringJavaSciprtAjaxHandler.
When using Java config, the AbstractFacesFlowConfiguration
base class automatically registers JsfResourceRequestHandler
so there is nothing further to do.
When using JSF with Spring Web Flow you can completely replace the JSF managed bean facility with a combination of Web Flow managed variables and Spring managed beans. It gives you a good deal more control over the lifecycle of your managed objects with well-defined hooks for initialization and execution of your domain model. Additionally, since you are presumably already using Spring for your business layer, it reduces the conceptual overhead of having to maintain two different managed bean models.
In doing pure JSF development, you will quickly find that request scope is not long-lived enough for storing conversational model objects that drive complex event-driven views. In JSF the usual option is to begin putting things into session scope, with the extra burden of needing to clean the objects up before progressing to another view or functional area of the application. What is really needed is a managed scope that is somewhere between request and session scope. JSF provides flash and view scopes that can be accessed programmatically via UIViewRoot.getViewMap(). Spring Web Flow provides access to flash, view, flow, and conversation scopes. These scopes are seamlessly integrated through JSF variable resolvers and work the same in all JSF applications.
The easiest and most natural way to declare and manage the model is through the use of flow variables. You can declare these variables at the beginning of the flow:
<var name="searchCriteria" class="com.mycompany.myapp.hotels.search.SearchCriteria"/>
and then reference this variable in one of the flow's JSF view templates through EL:
<h:inputText id="searchString" value="#{searchCriteria.searchString}"/>
Note that you do not need to prefix the variable with its scope when referencing it from the template (though you can do so if you need to be more specific). As with standard JSF beans, all available scopes will be searched for a matching variable, so you could change the scope of the variable in your flow definition without having to modify the EL expressions that reference it.
You can also define view instance variables that are scoped to the current view and get cleaned up automatically upon transitioning to another view. This is quite useful with JSF as views are often constructed to handle multiple in-page events across many requests before transitioning to another view.
To define a view instance variable, you can use the
var element inside a view-state
definition:
<view-state id="enterSearchCriteria"> <var name="searchCriteria" class="com.mycompany.myapp.hotels.search.SearchCriteria"/> </view-state>
Though defining autowired flow instance variables provides nice modularization and readability, occasions may arise where you want to utilize the other capabilities of the Spring container such as AOP. In these cases, you can define a bean in your Spring ApplicationContext and give it a specific web flow scope:
<bean id="searchCriteria" class="com.mycompany.myapp.hotels.search.SearchCriteria" scope="flow"/>
The major difference with this approach is that the bean will not be fully initialized until it is first accessed via an EL expression. This sort of lazy instantiation via EL is quite similar to how JSF managed beans are typically allocated.
The need to initialize the model before view rendering (such as by loading persistent entities from a database) is quite common, but JSF by itself does not provide any convenient hooks for such initialization. The flow definition language provides a natural facility for this through its Actions . Spring Web Flow provides some extra conveniences for converting the outcome of an action into a JSF-specific data structure. For example:
<on-render> <evaluate expression="bookingService.findBookings(currentUser.name)" result="viewScope.bookings" result-type="dataModel" /> </on-render>
This will take the result of the
bookingService.findBookings method an wrap it in a custom
JSF DataModel so that the list can be used in a standard JSF DataTable
component:
<h:dataTable id="bookings" styleClass="summary" value="#{bookings}" var="booking" rendered="#{bookings.rowCount > 0}"> <h:column> <f:facet name="header">Name</f:facet> #{booking.hotel.name} </h:column> <h:column> <f:facet name="header">Confirmation number</f:facet> #{booking.id} </h:column> <h:column> <f:facet name="header">Action</f:facet> <h:commandLink id="cancel" value="Cancel" action="cancelBooking" /> </h:column> </h:dataTable>
In the example above result-type="dataModel" results in the
wrapping of List<Booking> with custom
DataModel type. The custom
DataModel provides extra conveniences such as
being serializable for storage beyond request scope as well as access to
the currently selected row in EL expressions. For example, on postback
from a view where the action event was fired by a component within a
DataTable, you can take action on the selected row's model
instance:
<transition on="cancelBooking"> <evaluate expression="bookingService.cancelBooking(bookings.selectedRow)" /> </transition>
Spring Web Flow provides two custom DataModel types:
OneSelectionTrackingListDataModel and
ManySelectionTrackingListDataModel. As the names
indicate they keep track of one or multiple selected rows. This is done
with the help of a
SelectionTrackingActionListener listener, which
responds to JSF action events and invokes the appopriate methods on the
SelectinAware data models to record the currently
clicked row.
To understand how this is configured, keep in mind the
FacesConversionService registers a
DataModelConverter against the alias "dataModel"
on startup. When result-type="dataModel" is used in a flow definition it
causes the DataModelConverter to be used. The
converter then wraps the given List with an instance of
OneSelectionTrackingListDataModel. To use the
ManySelectionTrackingListDataModel you will need
to register your own custom converter.
Spring Web Flow allows you to handle JSF action events in a decoupled way, requiring no direct dependencies in your Java code on JSF API's. In fact, these events can often be handled completely in the flow definiton language without requiring any custom Java action code at all. This allows for a more agile development process since the artifacts being manipulated in wiring up events (JSF view templates and SWF flow definitions) are instantly refreshable without requiring a build and re-deploy of the whole application.
A simple but common case in JSF is the need to signal an event
that causes manipulation of the model in some way and then redisplays
the same view to reflect the changed state of the model. The flow
definition language has special support for this in the
transition element.
A good example of this is a table of paged list results. Suppose
you want to be able to load and display only a portion of a large result
list, and allow the user to page through the results. The initial
view-state definition to load and display the list would
be:
<view-state id="reviewHotels"> <on-render> <evaluate expression="bookingService.findHotels(searchCriteria)" result="viewScope.hotels" result-type="dataModel" /> </on-render> </view-state>
You construct a JSF DataTable that displays the current
hotels list, and then place a "More Results" link below the
table:
<h:commandLink id="nextPageLink" value="More Results" action="next"/>
This commandLink signals a "next" event from its action attribute.
You can then handle the event by adding to the view-state
definition:
<view-state id="reviewHotels"> <on-render> <evaluate expression="bookingService.findHotels(searchCriteria)" result="viewScope.hotels" result-type="dataModel" /> </on-render> <transition on="next"> <evaluate expression="searchCriteria.nextPage()" /> </transition> </view-state>
Here you handle the "next" event by incrementing the page count on
the searchCriteria instance. The on-render action is then
called again with the updated criteria, which causes the next page of
results to be loaded into the DataModel. The same view is re-rendered
since there was no to attribute on the
transition element, and the changes in the model are
reflected in the view.
The next logical level beyond in-page events are events that require navigation to another view, with some manipulation of the model along the way. Achieving this with pure JSF would require adding a navigation rule to faces-config.xml and likely some intermediary Java code in a JSF managed bean (both tasks requiring a re-deploy). With the flow defintion language, you can handle such a case concisely in one place in a quite similar way to how in-page events are handled.
Continuing on with our use case of manipulating a paged list of
results, suppose we want each row in the displayed DataTable to contain
a link to a detail page for that row instance. You can add a column to
the table containing the following commandLink
component:
<h:commandLink id="viewHotelLink" value="View Hotel" action="select"/>
This raises the "select" event which you can then handle by adding
another transition element to the existing
view-state :
<view-state id="reviewHotels"> <on-render> <evaluate expression="bookingService.findHotels(searchCriteria)" result="viewScope.hotels" result-type="dataModel" /> </on-render> <transition on="next"> <evaluate expression="searchCriteria.nextPage()" /> </transition> <transition on="select" to="reviewHotel"> <set name="flowScope.hotel" value="hotels.selectedRow" /> </transition> </view-state>
Here the "select" event is handled by pushing the currently
selected hotel instance from the DataTable into flow scope, so that it
may be referenced by the "reviewHotel" view-state .
JSF provides useful facilities for validating input at field-level before changes are applied to the model, but when you need to then perform more complex validation at the model-level after the updates have been applied, you are generally left with having to add more custom code to your JSF action methods in the managed bean. Validation of this sort is something that is generally a responsibility of the domain model itself, but it is difficult to get any error messages propagated back to the view without introducing an undesirable dependency on the JSF API in your domain layer.
With Web Flow, you can utilize the generic and low-level
MessageContext in your business code and any messages added
there will then be available to the FacesContext at render
time.
For example, suppose you have a view where the user enters the
necessary details to complete a hotel booking, and you need to ensure
the Check In and Check Out dates adhere to a given set of business
rules. You can invoke such model-level validation from a
transition element:
<view-state id="enterBookingDetails"> <transition on="proceed" to="reviewBooking"> <evaluate expression="booking.validateEnterBookingDetails(messageContext)" /> </transition> </view-state>
Here the "proceed" event is handled by invoking a model-level
validation method on the booking instance, passing the generic
MessageContext instance so that messages may be recorded.
The messages can then be displayed along with any other JSF messages
with the h:messages component,
JSF provides built-in support for sending Ajax requests and performing partial processing and rendering on the server-side. You can specify a list of id's for partial rendering through the <f:ajax> facelets tag.
In Spring Web Flow you also have the option to specify the ids to use for partial rendering on the server side with the render action:
<view-state id="reviewHotels"> <on-render> <evaluate expression="bookingService.findHotels(searchCriteria)" result="viewScope.hotels" result-type="dataModel" /> </on-render> <transition on="next"> <evaluate expression="searchCriteria.nextPage()" /> <render fragments="hotels:searchResultsFragment" /> </transition> </view-state>
By default when a flow enters a view state, it executes a client-side redirect before rendering the view. This approach is known as POST-REDIRECT-GET. It has the advantage of separating the form processing for one view from the rendering of the next view. As a result the browser Back and Refresh buttons work seamlessly without causing any browser warnings.
Normally the client-side redirect is transparent from a user's perspective. However, there are situations where POST-REDIRECT-GET may not bring the same benefits. For example sometimes it may be useful to embed a flow on a page and drive it via Ajax requests refreshing only the area of the page where the flow is rendered. Not only is it unnecessary to use client-side redirects in this case, it is also not the desired behavior with regards to keeping the surrounding content of the page intact.
To indicate a flow should execute in "page embedded" mode all you need to do is pass an extra flow input attribute called "mode" with a value of "embedded". Below is an example of a top-level container flow invoking a sub-flow in an embedded mode:
<subflow-state id="bookHotel" subflow="booking"> <input name="mode" value="'embedded'"/> </subflow-state>
When launched in "page embedded" mode the sub-flow will not issue flow execution redirects during Ajax requests.
If you'd like to see examples of an embedded flow please refer to the webflow-primefaces-showcase project. You can check out the source code locally, build it as you would a Maven project, and import it into Eclipse:
cd some-directory svn co https://src.springframework.org/svn/spring-samples/webflow-primefaces-showcase cd webflow-primefaces-showcase mvn package # import into Eclipse
The specific example you need to look at is under the "Advanced Ajax" tab and is called "Top Flow with Embedded Sub-Flow".
By default Web Flow does a client-side redirect even it it remains in the same view state as long as the current request is not an Ajax request. This is quite useful after form validation failures for example. If the user hits Refresh or Back they won't see any browser warnings. They would if the Web Flow didn't do a redirect.
This can lead to a problem specific to JSF environments where a specific Sun Mojarra listener component caches the FacesContext assuming the same instance is available throughout the JSF lifecycle. In Web Flow however the render phase is temporarily put on hold and a client-side redirect executed.
The default behavior of Web Flow is desirable and it is unlikely JSF applications will experience the issue. This is because Ajax is often enabled the default in JSF component libraries and Web Flow does not redirect during Ajax requests. However if you experience this issue you can disable client-side redirects within the same view as follows:
<webflow:flow-executor id="flowExecutor"> <webflow:flow-execution-attributes> <webflow:redirect-in-same-state value="false"/> </webflow:flow-execution-attributes> </webflow:flow-executor>
Most JSF component providers include some form of 'file upload' component. Generally when working
with these components JSF must take complete control of parsing multi-part requests and Spring MVC's
MultipartResolver cannot be used.
Spring Web Flow has been tested with file upload components from PrimeFaces. Check the documentation of your JSF component library for other providers to see how to configure file upload.
PrimeFaces provides a <p:fileUpload> component for uploading files. In order
to use the component you need to configure the org.primefaces.webapp.filter.FileUploadFilter
servlet filter. The filter needs to be configured against Spring MVC's
DispatcherServlet in your web.xml:
<filter> <filter-name>PrimeFaces FileUpload Filter</filter-name> <filter-class>org.primefaces.webapp.filter.FileUploadFilter</filter-class> </filter> <filter-mapping> <filter-name>PrimeFaces FileUpload Filter</filter-name> <servlet-name>Spring MVC Dispatcher Servlet</servlet-name> </filter-mapping> <context-param> <param-name>primefaces.UPLOADER</param-name> <param-value>commons</param-value> </context-param>
For more details refer to the PrimeFaces documentation.
To use the library you'll need to create a .taglib.xml
file and register it in web.xml.
Create the file
/WEB-INF/springsecurity.taglib.xml with the following
content:
<?xml version="1.0"?> <!DOCTYPE facelet-taglib PUBLIC "-//Sun Microsystems, Inc.//DTD Facelet Taglib 1.0//EN" "http://java.sun.com/dtd/facelet-taglib_1_0.dtd"> <facelet-taglib> <namespace>http://www.springframework.org/security/tags</namespace> <tag> <tag-name>authorize</tag-name> <handler-class>org.springframework.faces.security.FaceletsAuthorizeTagHandler</handler-class> </tag> <function> <function-name>areAllGranted</function-name> <function-class>org.springframework.faces.security.FaceletsAuthorizeTagUtils</function-class> <function-signature>boolean areAllGranted(java.lang.String)</function-signature> </function> <function> <function-name>areAnyGranted</function-name> <function-class>org.springframework.faces.security.FaceletsAuthorizeTagUtils</function-class> <function-signature>boolean areAnyGranted(java.lang.String)</function-signature> </function> <function> <function-name>areNotGranted</function-name> <function-class>org.springframework.faces.security.FaceletsAuthorizeTagUtils</function-class> <function-signature>boolean areNotGranted(java.lang.String)</function-signature> </function> <function> <function-name>isAllowed</function-name> <function-class>org.springframework.faces.security.FaceletsAuthorizeTagUtils</function-class> <function-signature>boolean isAllowed(java.lang.String, java.lang.String)</function-signature> </function> </facelet-taglib>
Next, register the above file taglib in web.xml:
<context-param> <param-name>javax.faces.FACELETS_LIBRARIES</param-name> <param-value>/WEB-INF/springsecurity.taglib.xml</param-value> </context-param>
Now you are ready to use the tag library in your views. You can use the authorize tag to include nested content conditionally:
<!DOCTYPE composition PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <ui:composition xmlns="http://www.w3.org/1999/xhtml" xmlns:ui="http://java.sun.com/jsf/facelets" xmlns:h="http://java.sun.com/jsf/html" xmlns:sec="http://www.springframework.org/security/tags"> <sec:authorize ifAllGranted="ROLE_FOO, ROLE_BAR"> Lorem ipsum dolor sit amet </sec:authorize> <sec:authorize ifNotGranted="ROLE_FOO, ROLE_BAR"> Lorem ipsum dolor sit amet </sec:authorize> <sec:authorize ifAnyGranted="ROLE_FOO, ROLE_BAR"> Lorem ipsum dolor sit amet </sec:authorize> </ui:composition>
You can also use one of several EL functions in the rendered or other attribute of any JSF component:
<!DOCTYPE composition PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <ui:composition xmlns="http://www.w3.org/1999/xhtml" xmlns:ui="http://java.sun.com/jsf/facelets" xmlns:h="http://java.sun.com/jsf/html" xmlns:sec="http://www.springframework.org/security/tags"> <!-- Rendered only if user has all of the listed roles --> <h:outputText value="Lorem ipsum dolor sit amet" rendered="#{sec:areAllGranted('ROLE_FOO, ROLE_BAR')}"/> <!-- Rendered only if user does not have any of the listed roles --> <h:outputText value="Lorem ipsum dolor sit amet" rendered="#{sec:areNotGranted('ROLE_FOO, ROLE_BAR')}"/> <!-- Rendered only if user has any of the listed roles --> <h:outputText value="Lorem ipsum dolor sit amet" rendered="#{sec:areAnyGranted('ROLE_FOO, ROLE_BAR')}"/> <!-- Rendered only if user has access to given HTTP method/URL as defined in Spring Security configuration --> <h:outputText value="Lorem ipsum dolor sit amet" rendered="#{sec:isAllowed('/secured/foo', 'POST')}"/> </ui:composition>
The Spring Web Flow JSF integration strives to be compatible with any third-party JSF component library. By honoring all of the standard semantics of the JSF specification within the SWF-driven JSF lifecycle, third-party libraries in general should "just work". The main thing to remember is that configuration in web.xml will change slightly since Web Flow requests are not routed through the standard FacesServlet. Typically, anything that is traditionally mapped to the FacesServlet should be mapped to the Spring DispatcherServlet instead. (You can also map to both if for example you are migrating a legacy JSF application page-by-page.).