一个客户的项目是使用 Spring Web Flow 2.0.5.RELEASE 编写的，我升级到了 2.3.2.RELEASE 版本。在某些流程中，我有这种过渡：
<transition on="save" to="index">
<evaluate expression="carTypeService.validateCarType(contextMessage, carType)" />
<evaluate expression="carTypeService.saveCarType(carType)" />
</transition>
这种过渡在旧版本中运行良好。在新版本中，我收到以下错误：
GRAVE：servlet Spring MVC Dispatcher Servlet 的 Servlet.service() 抛出异常
org.springframework.expression.spel.SpelEvaluationException: EL1008E:(pos 21): Field or property 'contextMessage' cannot be found on object of type 'org.springframework.webflow.engine.impl.RequestControlContextImpl'
at org.springframework.expression.spel.ast.PropertyOrFieldReference.readProperty(PropertyOrFieldReference.java:246)
at org.springframework.expression.spel.ast.PropertyOrFieldReference.getValueInternal(PropertyOrFieldReference.java:112)
at org.springframework.expression.spel.ast.PropertyOrFieldReference.getValueInternal(PropertyOrFieldReference.java:107)
at org.springframework.expression.spel.ast.MethodReference.getValueRef(MethodReference.java:125)
at org.springframework.expression.spel.ast.CompoundExpression.getValueRef(CompoundExpression.java:62)
at org.springframework.expression.spel.ast.CompoundExpression.getValueInternal(CompoundExpression.java:81)
at org.springframework.expression.spel.ast.SpelNodeImpl.getTypedValue(SpelNodeImpl.java:102)
at org.springframework.expression.spel.standard.SpelExpression.getValue(SpelExpression.java:98)
at org.springframework.binding.expression.spel.SpringELExpression.getValue(SpringELExpression.java:84)
at org.springframework.webflow.action.EvaluateAction.doExecute(EvaluateAction.java:75)
at org.springframework.webflow.action.AbstractAction.execute(AbstractAction.java:188)
at org.springframework.webflow.execution.AnnotatedAction.execute(AnnotatedAction.java:145)
at org.springframework.webflow.execution.ActionExecutor.execute(ActionExecutor.java:51)
at org.springframework.webflow.engine.support.ActionTransitionCriteria.test(ActionTransitionCriteria.java:82)
at org.springframework.webflow.engine.support.TransitionCriteriaChain.test(TransitionCriteriaChain.java:71)
at org.springframework.webflow.engine.Transition.canExecute(Transition.java:195)
at org.springframework.webflow.engine.Transition.execute(Transition.java:211)
at org.springframework.webflow.engine.impl.FlowExecutionImpl.execute(FlowExecutionImpl.java:393)
at org.springframework.webflow.engine.impl.RequestControlContextImpl.execute(RequestControlContextImpl.java:214)
at org.springframework.webflow.engine.TransitionableState.handleEvent(TransitionableState.java:119)
at org.springframework.webflow.engine.Flow.handleEvent(Flow.java:555)
at org.springframework.webflow.engine.impl.FlowExecutionImpl.handleEvent(FlowExecutionImpl.java:388)
at org.springframework.webflow.engine.impl.RequestControlContextImpl.handleEvent(RequestControlContextImpl.java:210)
at org.springframework.webflow.engine.ViewState.handleEvent(ViewState.java:232)
at org.springframework.webflow.engine.ViewState.resume(ViewState.java:196)
at org.springframework.webflow.engine.Flow.resume(Flow.java:545)
at org.springframework.webflow.engine.impl.FlowExecutionImpl.resume(FlowExecutionImpl.java:258)
at org.springframework.webflow.executor.FlowExecutorImpl.resumeExecution(FlowExecutorImpl.java:169)
at org.springframework.webflow.mvc.servlet.FlowHandlerAdapter.handle(FlowHandlerAdapter.java:183)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:925)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:856)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:920)
at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:827)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:643)
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:801)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:723)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.myfaces.webapp.filter.ExtensionsFilter.doFilter(ExtensionsFilter.java:374)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.ajax4jsf.webapp.BaseXMLFilter.doXmlFilter(BaseXMLFilter.java:178)
at org.ajax4jsf.webapp.BaseFilter.handleRequest(BaseFilter.java:290)
at org.ajax4jsf.webapp.BaseFilter.processUploadsAndHandleRequest(BaseFilter.java:368)
at org.ajax4jsf.webapp.BaseFilter.doFilter(BaseFilter.java:495)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.springframework.orm.jpa.support.OpenEntityManagerInViewFilter.doFilterInternal(OpenEntityManagerInViewFilter.java:180)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330)
at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:118)
at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:84)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:113)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:103)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:113)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:54)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:45)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.authentication.www.BasicAuthenticationFilter.doFilter(BasicAuthenticationFilter.java:150)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:183)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:105)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:87)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
...
根据官方文档，我可以像在旧版本中一样在流中使用该变量。
我知道这messageContext是在org.springframework.binding.message.MessageContext课堂上实现的，但我应该如何将它引用到 XML 中？