如何在JSP中将空变量传递给Spring表达式

我正在JSP中使用

标记：

其中

today

是一个java.util.Date。只要today变量不为null，一切正常。当今天

为空时，我得到

org.springframework.expression.spel.SpelEvaluationException: EL1007E:(pos 0): Field or property 'today' cannot be found on null
    org.springframework.expression.spel.ast.PropertyOrFieldReference.readProperty(PropertyOrFieldReference.java:243)
    org.springframework.expression.spel.ast.PropertyOrFieldReference.getValueInternal(PropertyOrFieldReference.java:112)
    org.springframework.expression.spel.ast.PropertyOrFieldReference.getValueInternal(PropertyOrFieldReference.java:107)
    org.springframework.expression.spel.ast.OpPlus.getValueInternal(OpPlus.java:70)
    org.springframework.expression.spel.ast.SpelNodeImpl.getTypedValue(SpelNodeImpl.java:102)
    org.springframework.expression.spel.standard.SpelExpression.getValue(SpelExpression.java:98)
    org.springframework.web.servlet.tags.EvalTag.doEndTag(EvalTag.java:126)
    org.apache.jsp.WEB_002dINF.views.admin.inbox_jsp._jspx_meth_s_005feval_005f1(inbox_jsp.java:195)
    org.apache.jsp.WEB_002dINF.views.admin.inbox_jsp._jspService(inbox_jsp.java:120)
    org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
    org.apache.jasper.runtime.JspRuntimeLibrary.include(JspRuntimeLibrary.java:954)
    org.apache.jasper.runtime.PageContextImpl.doInclude(PageContextImpl.java:684)
    org.apache.jasper.runtime.PageContextImpl.include(PageContextImpl.java:678)
    org.apache.tiles.request.jsp.JspRequest.doInclude(JspRequest.java:123)
    org.apache.tiles.request.AbstractViewRequest.dispatch(AbstractViewRequest.java:47)
    org.apache.tiles.request.render.DispatchRenderer.render(DispatchRenderer.java:45)
    org.apache.tiles.request.render.ChainedDelegateRenderer.render(ChainedDelegateRenderer.java:68)
    org.apache.tiles.impl.BasicTilesContainer.render(BasicTilesContainer.java:259)
    org.apache.tiles.template.InsertAttributeModel.renderAttribute(InsertAttributeModel.java:188)
    org.apache.tiles.template.InsertAttributeModel.execute(InsertAttributeModel.java:132)
    org.apache.tiles.jsp.taglib.InsertAttributeTag.doTag(InsertAttributeTag.java:299)
    org.apache.jsp.WEB_002dINF.views.common.main_002dlayout_jsp._jspx_meth_tiles_005finsertAttribute_005f2(main_002dlayout_jsp.java:243)
    org.apache.jsp.WEB_002dINF.views.common.main_002dlayout_jsp._jspService(main_002dlayout_jsp.java:103)
    org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
    org.apache.tiles.request.servlet.ServletRequest.forward(ServletRequest.java:265)
    org.apache.tiles.request.servlet.ServletRequest.doForward(ServletRequest.java:228)
    org.apache.tiles.request.AbstractClientRequest.dispatch(AbstractClientRequest.java:57)
    org.apache.tiles.request.render.DispatchRenderer.render(DispatchRenderer.java:45)
    org.apache.tiles.impl.BasicTilesContainer.render(BasicTilesContainer.java:259)
    org.apache.tiles.impl.BasicTilesContainer.render(BasicTilesContainer.java:397)
    org.apache.tiles.impl.BasicTilesContainer.render(BasicTilesContainer.java:238)
    org.apache.tiles.impl.BasicTilesContainer.render(BasicTilesContainer.java:221)
    org.apache.tiles.renderer.DefinitionRenderer.render(DefinitionRenderer.java:59)
    org.springframework.web.servlet.view.tiles3.TilesView.renderMergedOutputModel(TilesView.java:145)
    org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:264)
    org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1208)
    org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:992)
    org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:939)
    org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:856)
    org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:936)
    org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:827)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
    org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:812)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
    org.springframework.orm.hibernate4.support.OpenSessionInViewFilter.doFilterInternal(OpenSessionInViewFilter.java:152)
    org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330)
    org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:118)
    org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:84)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:113)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:103)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:113)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:54)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:45)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    org.springframework.security.web.authentication.www.BasicAuthenticationFilter.doFilter(BasicAuthenticationFilter.java:150)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:183)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:105)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:87)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:192)
    org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:160)
    org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:346)
    org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:259)
org.springframework.expression.spel.SpelEvaluationException:EL1007E:（位置0）：在null上找不到字段或属性“today”
org.springframework.expression.spel.ast.PropertyOrFieldReference.readProperty（PropertyOrFieldReference.java:243）
org.springframework.expression.spel.ast.PropertyOrFieldReference.getValueInternal（PropertyOrFieldReference.java:112）
org.springframework.expression.spel.ast.PropertyOrFieldReference.getValueInternal（PropertyOrFieldReference.java:107）
org.springframework.expression.spel.ast.OpPlus.getValueInternal（OpPlus.java:70）
org.springframework.expression.spel.ast.SpelNodeImpl.getTypedValue（SpelNodeImpl.java:102）
org.springframework.expression.spel.standard.SpelExpression.getValue（SpelExpression.java:98）
org.springframework.web.servlet.tags.EvalTag.doEndTag（EvalTag.java:126）
org.apache.jsp.WEB\u 002dINF.views.admin.inbox\u jsp.\u jspx\u meth\u s\u 005feval\u 005f1（inbox\u jsp.java:195）
org.apache.jsp.WEB\u 002dINF.views.admin.inbox\u jsp.\u jsp服务（inbox\u jsp.java:120）
org.apache.jasper.runtime.HttpJspBase.service（HttpJspBase.java:70）
javaservlet.http.HttpServlet.service（HttpServlet.java:728）
org.apache.jasper.servlet.JspServletWrapper.service（JspServletWrapper.java:432）
org.apache.jasper.servlet.JspServlet.serviceJspFile（JspServlet.java:390）
org.apache.jasper.servlet.JspServlet.service（JspServlet.java:334）
javaservlet.http.HttpServlet.service（HttpServlet.java:728）
org.apache.jasper.runtime.JspRuntimeLibrary.include（JspRuntimeLibrary.java:954）
org.apache.jasper.runtime.PageContextImpl.doInclude（PageContextImpl.java:684）
org.apache.jasper.runtime.PageContextImpl.include（PageContextImpl.java:678）
org.apache.tiles.request.jsp.JspRequest.doInclude（JspRequest.java:123）
org.apache.tiles.request.AbstractViewRequest.dispatch（AbstractViewRequest.java:47）
org.apache.tiles.request.render.DispatchRenderer.render（DispatchRenderer.java:45）
org.apache.tiles.request.render.ChainedDelegateRenderer.render（ChainedDelegateRenderer.java:68）
org.apache.tiles.impl.BasicTilesContainer.render（BasicTilesContainer.java:259）
org.apache.tiles.template.InsertAttributeModel.renderAttribute（InsertAttributeModel.java:188）
org.apache.tiles.template.InsertAttributeModel.execute（InsertAttributeModel.java:132）
org.apache.tiles.jsp.taglib.InsertAttributeTag.doTag（InsertAttributeTag.java:299）
org.apache.jsp.WEB\u 002dINF.views.common.main\u 002drayout\u jsp.\u jspx\u meth\u tiles\u 005finsertatAttribute\u 005f2（main\u 002drayout\u jsp.java:243）
org.apache.jsp.WEB\u 002dINF.views.common.main\u 002dlaway\u jsp.\u jsp服务（main\u 002dlaway\u jsp.java:103）
org.apache.jasper.runtime.HttpJspBase.service（HttpJspBase.java:70）
javaservlet.http.HttpServlet.service（HttpServlet.java:728）
org.apache.jasper.servlet.JspServletWrapper.service（JspServletWrapper.java:432）
org.apache.jasper.servlet.JspServlet.serviceJspFile（JspServlet.java:390）
org.apache.jasper.servlet.JspServlet.service（JspServlet.java:334）
javaservlet.http.HttpServlet.service（HttpServlet.java:728）
org.apache.tiles.request.servlet.ServletRequest.forward（ServletRequest.java:265）
org.apache.tiles.request.servlet.ServletRequest.doForward（ServletRequest.java:228）
org.apache.tiles.request.AbstractClientRequest.dispatch（AbstractClientRequest.java:57）
org.apache.tiles.request.render.DispatchRenderer.render（DispatchRenderer.java:45）
org.apache.tiles.impl.BasicTilesContainer.render（BasicTilesContainer.java:259）
org.apache.tiles.impl.BasicTilesContainer.render（BasicTilesContainer.java:397）
org.apache.tiles.impl.BasicTilesContainer.render（BasicTilesContainer.java:238）
org.apache.tiles.impl.BasicTilesContainer.render（BasicTilesContainer.java:221）
org.apache.tiles.renderer.DefinitionRenderer.render（DefinitionRenderer.java:59）
org.springframework.web.servlet.view.tiles3.TilesView.renderMergedOutputModel（TilesView.java:145）
org.springframework.web.servlet.view.AbstractView.render（AbstractView.java:264）
org.springframework.web.servlet.DispatcherServlet.render（DispatcherServlet.java:1208）
org.springframework.web.servlet.DispatcherServlet.processDispatchResult（DispatcherServlet.java:992）
org.springframework.web.servlet.DispatcherServlet.doDispatch（DispatcherServlet.java:939）
org.springframework.web.servlet.DispatcherServlet.doService（DispatcherServlet.java:856）
org.springframework.web.servlet.FrameworkServlet.processRequest（FrameworkServlet.java:936）
org.springframework.web.servlet.FrameworkServlet.doGet（FrameworkServlet.java:827）
javaservlet.http.HttpServlet.service（HttpServlet.java:621）
org.springframework.web.servlet.FrameworkServlet.service（FrameworkServlet.java:812）
javaservlet.http.HttpServlet.service（HttpServlet.java:728）
org.springframework.orm.hibernate4.support.OpenSessionInViewFilter.doFilterInternal（OpenSessionInViewFilter.java:152）
org.springframework.web.filter.OncePerRequestFilter.doFilter（OncePerRequestFilter.java:107）
org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter（FilterChainProxy.java:330）
org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke（FilterSecurityInterceptor.java:118）
org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter（FilterSecurityInterceptor.java:84）
org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter（FilterChainProxy.java:342）
org.springframework.security.web.access.ExceptionTranslationFilter.doFilter（ExceptionTranslationFilter.java:113）
org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter（FilterChai
<spring:eval expression="'today is ' + requestScope['today']" />

<spring:eval expression="'today is ' + sessionScope['today']" />