Assert: The expression string to parse is required and must not empty

Buang masa juga DEBUG ERROR ni, hanya kerana TRY & ERROR.

 Punca: 

 <display:column>  
      <form:checkbox path="studyPlanDetailList[${spd_rowNum-1}].selected" value="Y" />  
 </display:column>  

 Sepatutnya:

 <display:column>  
      <form:checkbox path="studyPlanDetailList[${spd_rowNum-1}].selected" value="Y">  
 </form:checkbox></display:column>  

Error:

 SEVERE: Servlet.service() for servlet apr threw exception  
 java.lang.IllegalArgumentException: The expression string to parse is required and must not be empty  
      at org.springframework.util.Assert.hasText(Assert.java:162)  
      at org.springframework.binding.expression.spel.SpringELExpressionParser.parseExpression(SpringELExpressionParser.java:72)  
      at org.springframework.webflow.mvc.view.AbstractMvcView.addEmptyValueMapping(AbstractMvcView.java:472)  
      at org.springframework.webflow.mvc.view.AbstractMvcView.addDefaultMappings(AbstractMvcView.java:454)  
      at org.springframework.webflow.mvc.view.AbstractMvcView.bind(AbstractMvcView.java:373)  
      at org.springframework.webflow.mvc.view.AbstractMvcView.processUserEvent(AbstractMvcView.java:216)  
      at org.springframework.webflow.engine.ViewState.handleEvent(ViewState.java:226)  
      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: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.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:790)  
      at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:719)  
      at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:644)  
      at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:560)  
      at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)  
      at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)  
      at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)  
      at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)  
      at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:77)  
      at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)  
      at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)  
      at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)  
      at com.opensymphony.sitemesh.webapp.SiteMeshFilter.obtainContent(SiteMeshFilter.java:129)  
      at com.opensymphony.sitemesh.webapp.SiteMeshFilter.doFilter(SiteMeshFilter.java:77)  
      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$VirtualFilterChain.doFilter(FilterChainProxy.java:368)  
      at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:109)  
      at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:83)  
      at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:380)  
      at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:97)  
      at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:380)  
      at org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:100)  
      at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:380)  
      at org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:78)  
      at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:380)  
      at org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:54)  
      at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:380)  
      at org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:35)  
      at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:380)  
      at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:187)  
      at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:380)  
      at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:105)  
      at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:380)  
      at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:79)  
      at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:380)  
      at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:169)  
      at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:237)  
      at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:167)  
      at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)  
      at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)  
      at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)  
      at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)  
      at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)  
      at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)  
      at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:615)  
      at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)  
      at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)  
      at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:859)  
      at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:602)  
      at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:409)  
      at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)  
      at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)  
      at java.lang.Thread.run(Thread.java:662)  

Persekitaran:

Spring, Spring Webflow, JSP, displaytag

Codename: APR