Spring Web Flow + Apache Tiles + Ajax - ajax

Question

I want to integrate Ajax and Apache Tiles with Spring Web Fow. Simple flow without Tiles is working fine, but it is throwing NullPointerException after integrating with Tiles.
Here is the Web Flow servlet:
<?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:p="http://www.springframework.org/schema/p"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xmlns:webflow="http://www.springframework.org/schema/webflow-config"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.0.xsd
http://www.springframework.org/schema/mvc
http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd
http://www.springframework.org/schema/webflow-config
http://www.springframework.org/schema/webflow-config/spring-webflow-config-2.3.xsd">
<bean id="transportWebFlow" class="com.demo.controller.DemoController"/>
<bean id="tilesViewResolver" class="org.springframework.web.servlet.view.UrlBasedViewResolver">
<property name="viewClass" value="org.springframework.web.servlet.view.tiles2.TilesView" />
<!-- <property name="prefix" value="/WEB-INF/jsp/"/>
<property name="suffix" value=".jsp"/> -->
</bean>
<!-- <bean id="tilesViewResolver" class="org.springframework.js.ajax.AjaxUrlBasedViewResolver">
<property name="viewClass" value="org.springframework.webflow.mvc.view.FlowAjaxTilesView"/>
</bean> -->
<bean class="org.springframework.web.servlet.view.tiles2.TilesConfigurer">
<property name="definitions">
<list>
<value>/WEB-INF/tilesDefination/demo.xml</value>
</list>
</property>
</bean>
<bean id="handlerMapping" class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping">
<property name="mappings">
<value>/*.html=flowController</value>
</property>
</bean>
<bean id="flowController" class="org.springframework.webflow.mvc.servlet.FlowController">
<property name="flowExecutor" ref="flowExecutor"/>
</bean>
<webflow:flow-executor id="flowExecutor" flow-registry="flowRegistry">
</webflow:flow-executor>
<webflow:flow-registry id="flowRegistry" base-path="/WEB-INF/flows/" flow-builder-services="flowBuilderServices">
<webflow:flow-location id="demo" path="demo-flow.xml" />
</webflow:flow-registry>
<webflow:flow-builder-services id="flowBuilderServices"
view-factory-creator="viewFactoryCreator" development="true"/>
<bean id="viewFactoryCreator" class="org.springframework.webflow.mvc.builder.MvcViewFactoryCreator">
<property name="viewResolvers" ref ="tilesViewResolver"/>
</bean>
</beans>
Tiles Configuration for webflow
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE tiles-definitions PUBLIC "-//Apache Software Foundation//DTD Tiles Configuration 2.1//EN"
"http://tiles.apache.org/dtds/tiles-config_2_1.dtd">
<tiles-definitions>
<definition name="base.demo" template="/WEB-INF/jsp/demoLayout.jsp">
<put-attribute name="title" value="Travel.com"/>
<put-attribute name="demoHeader" value="/WEB-INF/jsp/demoHeader.jsp"/>
<put-attribute name="demoBody" value=""/>
<put-attribute name="demoFooter" value="/WEB-INF/jsp/demoFooter.jsp"/>
</definition>
<definition name="demo" extends="base.demo">
<put-attribute name="demoBody" value="/WEB-INF/jsp/demo.jsp"/>
</definition>
</tiles-definitions>
demo.xml
<?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-2.0.xsd">
<var name="demo" class="com.demo.model.Demo"/>
<view-state id="demo" view="/WEB-INF/jsp/demo.jsp" model="demo">
</view-state>
</flow>
Controller
package com.demo.controller;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.servlet.ModelAndView;
import com.demo.model.Demo;
#Controller
public class DemoController {
#RequestMapping(value="demo.html",method=RequestMethod.GET)
public ModelAndView demo(){
Demo demo = new Demo();
return new ModelAndView("demo","demo", demo);
}
}
This is the exception stack trace:
SEVERE: Servlet.service() for servlet [SpringFlow] in context with path [/DemoWebFlow] threw exception [Request processing failed; nested exception is org.springframework.webflow.execution.FlowExecutionException: Exception thrown in state 'demo' of flow 'demo'] with root cause
java.lang.NullPointerException
at org.springframework.webflow.mvc.servlet.ServletMvcView.doRender(ServletMvcView.java:50)
at org.springframework.webflow.mvc.view.AbstractMvcView.render(AbstractMvcView.java:187)
at org.springframework.webflow.engine.ViewState.render(ViewState.java:296)
at org.springframework.webflow.engine.ViewState.refresh(ViewState.java:243)
at org.springframework.webflow.engine.ViewState.resume(ViewState.java:221)
at org.springframework.webflow.engine.Flow.resume(Flow.java:545)
at org.springframework.webflow.engine.impl.FlowExecutionImpl.resume(FlowExecutionImpl.java:261)
at org.springframework.webflow.executor.FlowExecutorImpl.resumeExecution(FlowExecutorImpl.java:169)
at org.springframework.webflow.mvc.servlet.FlowHandlerAdapter.handle(FlowHandlerAdapter.java:183)
at org.springframework.webflow.mvc.servlet.FlowController.handleRequest(FlowController.java:174)
at org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter.handle(SimpleControllerHandlerAdapter.java:48)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:771)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:716)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:647)
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:552)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:953)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1008)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:312)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)