title: use checkbox within iterator in strut 2.0
body: <p>In my sample application this worked perfect </p>
  
  <pre><code>&lt;s:iterator value="menuGroup" var="menu"&gt;
                  &lt;s:textfield value="%{#menu.name}"&gt;&lt;/s:textfield&gt;
              &lt;/s:iterator&gt;
  </code></pre>
  
  <p>but when i use checkbox instead i.e `</p>
  
  <pre><code>&lt;s:iterator value="menuGroup" var="menuLst"&gt;
                  &lt;s:checkbox value="%{menuLst.name}"&gt;&lt;/s:checkbox&gt;
              &lt;/s:iterator&gt;
  </code></pre>
  
  <p>it gives an error like </p>
  
  <pre><code>freemarker.core.InvalidReferenceException: Expression parameters.name is undefined on line 23, column 56 in template/xhtml/checkbox.ftl.
      at freemarker.core.TemplateObject.assertNonNull(TemplateObject.java:124)
      at freemarker.core.DynamicKeyName._getAsTemplateModel(DynamicKeyName.java:85)
      at freemarker.core.Expression.getAsTemplateModel(Expression.java:89)
      at freemarker.core.ExistsExpression._getAsTemplateModel(ExistsExpression.java:71)
      at freemarker.core.Expression.getAsTemplateModel(Expression.java:89)
      at freemarker.core.Expression.isTrue(Expression.java:138)
      at freemarker.core.AndExpression.isTrue(AndExpression.java:68)
      at freemarker.core.BooleanExpression._getAsTemplateModel(BooleanExpression.java:61)
      at freemarker.core.Expression.getAsTemplateModel(Expression.java:89)
      at freemarker.core.Assignment.accept(Assignment.java:90)
      at freemarker.core.Environment.visit(Environment.java:208)
      at freemarker.core.MixedContent.accept(MixedContent.java:92)
      at freemarker.core.Environment.visit(Environment.java:208)
      at freemarker.core.Environment.process(Environment.java:188)
      at freemarker.template.Template.process(Template.java:237)
      at org.apache.struts2.components.template.FreemarkerTemplateEngine.renderTemplate(FreemarkerTemplateEngine.java:182)
      at org.apache.struts2.components.UIBean.mergeTemplate(UIBean.java:559)
      at org.apache.struts2.components.UIBean.end(UIBean.java:513)
      at org.apache.struts2.views.jsp.ComponentTagSupport.doEndTag(ComponentTagSupport.java:42)
      at org.apache.jsp.jsp.pages.system.acl_002dgroup_jsp._jspx_meth_s_005fcheckbox_005f0(acl_002dgroup_jsp.java:440)
      at org.apache.jsp.jsp.pages.system.acl_002dgroup_jsp._jspx_meth_s_005fiterator_005f0(acl_002dgroup_jsp.java:411)
      at org.apache.jsp.jsp.pages.system.acl_002dgroup_jsp._jspx_meth_s_005fform_005f0(acl_002dgroup_jsp.java:368)
      at org.apache.jsp.jsp.pages.system.acl_002dgroup_jsp._jspService(acl_002dgroup_jsp.java:317)
      at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
      at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
      at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:369)
      at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:322)
      at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:249)
      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.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:638)
      at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:444)
      at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:382)
      at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:310)
      at org.apache.struts2.dispatcher.ServletDispatcherResult.doExecute(ServletDispatcherResult.java:154)
      at org.apache.struts2.dispatcher.StrutsResultSupport.execute(StrutsResultSupport.java:186)
      at com.opensymphony.xwork2.DefaultActionInvocation.executeResult(DefaultActionInvocation.java:361)
      at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:265)
      at com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:163)
      at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87)
      at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236)
      at com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:249)
      at org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:68)
      at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87)
      at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236)
      at com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.intercept(ConversionErrorInterceptor.java:122)
      at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236)
      at com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:195)
      at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87)
      at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236)
      at com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:195)
      at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87)
      at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236)
      at com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.java:148)
      at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236)
      at org.apache.struts2.interceptor.CheckboxInterceptor.intercept(CheckboxInterceptor.java:93)
      at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236)
      at org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:235)
      at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236)
      at com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor.intercept(ModelDrivenInterceptor.java:89)
      at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236)
      at com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor.intercept(ScopedModelDrivenInterceptor.java:128)
      at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236)
      at org.apache.struts2.interceptor.ProfilingActivationInterceptor.intercept(ProfilingActivationInterceptor.java:104)
      at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236)
      at org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:267)
      at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236)
      at com.opensymphony.xwork2.interceptor.ChainingInterceptor.intercept(ChainingInterceptor.java:126)
      at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236)
      at com.opensymphony.xwork2.interceptor.PrepareInterceptor.doIntercept(PrepareInterceptor.java:138)
      at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87)
      at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236)
      at com.opensymphony.xwork2.interceptor.I18nInterceptor.intercept(I18nInterceptor.java:148)
      at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236)
      at org.apache.struts2.interceptor.ServletConfigInterceptor.intercept(ServletConfigInterceptor.java:164)
      at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236)
      at com.opensymphony.xwork2.interceptor.AliasInterceptor.intercept(AliasInterceptor.java:128)
      at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236)
      at com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:176)
      at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236)
      at org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:52)
      at org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:468)
      at org.apache.struts2.dispatcher.FilterDispatcher.
  </code></pre>