template/simple/select.ftl出错

Error on line 69, column 13 in template/simple/select.ftlstack.findValue('top') is undefined.It cannot be assigned to itemKeyThe problematic instruction:----------==> assignment: itemKey=stack.findValue('top') [on line 69, column 13 in template/simple/select.ftl] in user-directive s.iterator [on line 59, column 1 in template/simple/select.ftl] in include "/${parameters.templateDir}/simple/select.ftl" [on line 24, column 1 in template/xhtml/select.ftl]----------Java backtrace for programmers:----------freemarker.core.InvalidReferenceException: Error on line 69, column 13 in template/simple/select.ftlstack.findValue('top') is undefined.It cannot be assigned to itemKeyat freemarker.core.Assignment.accept(Assignment.java:111)at freemarker.core.Environment.visit(Environment.java:221)at freemarker.core.MixedContent.accept(MixedContent.java:92)at freemarker.core.Environment.visit(Environment.java:221)at freemarker.core.IfBlock.accept(IfBlock.java:82)at freemarker.core.Environment.visit(Environment.java:221)at freemarker.core.MixedContent.accept(MixedContent.java:92)at freemarker.core.Environment.visit(Environment.java:221)at freemarker.core.Environment.visit(Environment.java:310)at freemarker.core.UnifiedCall.accept(UnifiedCall.java:130)at freemarker.core.Environment.visit(Environment.java:221)at freemarker.core.MixedContent.accept(MixedContent.java:92)at freemarker.core.Environment.visit(Environment.java:221)at freemarker.core.Environment.include(Environment.java:1508)at freemarker.core.Include.accept(Include.java:169)at freemarker.core.Environment.visit(Environment.java:221)at freemarker.core.MixedContent.accept(MixedContent.java:92)at freemarker.core.Environment.visit(Environment.java:221)at freemarker.core.Environment.process(Environment.java:199)at freemarker.template.Template.process(Template.java:259)at org.apache.struts2.components.template.FreemarkerTemplateEngine.renderTemplate(FreemarkerTemplateEngine.java:157)at org.apache.struts2.components.UIBean.mergeTemplate(UIBean.java:565)at org.apache.struts2.components.UIBean.end(UIBean.java:519)at org.apache.struts2.views.jsp.ComponentTagSupport.doEndTag(ComponentTagSupport.java:42)at org.apache.jsp.WEB_002dINF.jsp.data.data_005fout_005flist_jsp._jspx_meth_s_005fselect_005f0(data_005fout_005flist_jsp.java:482)at org.apache.jsp.WEB_002dINF.jsp.data.data_005fout_005flist_jsp._jspx_meth_s_005fif_005f0(data_005fout_005flist_jsp.java:441)at org.apache.jsp.WEB_002dINF.jsp.data.data_005fout_005flist_jsp._jspService(data_005fout_005flist_jsp.java:177)at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:443)at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:385)at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:329)at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:230)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:715)at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:460)at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:385)at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:311)at org.apache.struts2.dispatcher.ServletDispatcherResult.doExecute(ServletDispatcherResult.java:164)at org.apache.struts2.dispatcher.StrutsResultSupport.execute(StrutsResultSupport.java:186)at com.opensymphony.xwork2.DefaultActionInvocation.executeResult(DefaultActionInvocation.java:374)at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:278)at org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:256)at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)at com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:176)at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)at com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:265)at org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:68)at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)at com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.intercept(ConversionErrorInterceptor.java:138)at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)at com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:236)at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)at com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:236)at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)at com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.java:190)at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)at org.apache.struts2.interceptor.MultiselectInterceptor.intercept(MultiselectInterceptor.java:75)at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)at org.apache.struts2.interceptor.CheckboxInterceptor.intercept(CheckboxInterceptor.java:90)at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)at org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:243)at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)at com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor.intercept(ModelDrivenInterceptor.java:100)at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)at com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor.intercept(ScopedModelDrivenInterceptor.java:141)at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)at com.opensymphony.xwork2.interceptor.ChainingInterceptor.intercept(ChainingInterceptor.java:145)at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)at com.opensymphony.xwork2.interceptor.PrepareInterceptor.doIntercept(PrepareInterceptor.java:171)at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)at com.opensymphony.xwork2.interceptor.I18nInterceptor.intercept(I18nInterceptor.java:176)at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)at org.apache.struts2.interceptor.ServletConfigInterceptor.intercept(ServletConfigInterceptor.java:164)at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)at com.opensymphony.xwork2.interceptor.AliasInterceptor.intercept(AliasInterceptor.java:192)at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)at com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:187)at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)at org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:54)at org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:511)at org.apache.struts2.dispatcher.ng.ExecuteOperations.executeAction(ExecuteOperations.java:77)at org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:91)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)at org.springframework.orm.hibernate3.support.OpenSessionInViewFilter.doFilterInternal(OpenSessionInViewFilter.java:230)at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199)at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:108)at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:620)at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:349)at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:784)at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:802)at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1452)at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)at java.lang.Thread.run(Thread.java:745)</xmp></pre></div></html>本人在使用Struts2的<s:select list="types">标签的时候，由于在数据库中查询出了空值，由于列表types中有空值之后，该标签就报如上错误，把types中的null去掉即可