HTTP Status 500 - 的错误

异常如下:
HTTP Status 500 - --------------------------------------------------------------------------------type Exception reportmessage description The server encountered an internal error () that prevented it from fulfilling this request.exception javax.servlet.ServletException: No selector attribute (cookie/header/name/parameter) was specified
org.apache.jasper.runtime.PageContextImpl.doHandlePageException(PageContextImpl.java:825)
org.apache.jasper.runtime.PageContextImpl.handlePageException(PageContextImpl.java:758)
org.apache.jsp.form.hello_jsp._jspService(hello_jsp.java:96)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:94)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:324)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:292)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:236)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
root cause javax.servlet.jsp.JspException: No selector attribute (cookie/header/name/parameter) was specified
org.apache.struts.taglib.logic.PresentTag.condition(PresentTag.java:99)
org.apache.struts.taglib.logic.PresentTag.condition(PresentTag.java:54)
org.apache.struts.taglib.logic.ConditionalTagBase.doStartTag(ConditionalTagBase.java:174)
org.apache.jsp.form.hello_jsp._jspx_meth_logic_present_0(hello_jsp.java:232)
org.apache.jsp.form.hello_jsp._jspx_meth_html_html_0(hello_jsp.java:138)
org.apache.jsp.form.hello_jsp._jspService(hello_jsp.java:87)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:94)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:324)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:292)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:236)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
note The full stack trace of the root cause is available in the Apache Tomcat/5.0.28 logs.不知道是什么问题呢