我在发布使用HDIV安全框架的新版应用程序之前的最后一步。
目前我通过登录页面访问此应用程序时收到NullPointerException。奇怪的是，我以前从未在同一页面上遇到过这种异常。但我昨天已经在另一页上遇到过这种例外。
知道为什么我会收到这个随机异常吗？
java.lang.NullPointerException
at org.hdiv.taglib.html.TextTagHDIV.doStartTag(TextTagHDIV.java:52)
at org.hdiv.strutsel.taglib.html.ELTextTagHDIV.doStartTag(ELTextTagHDIV.java:926)
at org.apache.jsp.login_jsp._jspx_meth_html_005ftext_005f0(login_jsp.java:421)
at org.apache.jsp.login_jsp._jspx_meth_html_005fform_005f0(login_jsp.java:345)
at org.apache.jsp.login_jsp._jspx_meth_html_005fhtml_005f0(login_jsp.java:229)
at org.apache.jsp.login_jsp._jspService(login_jsp.java:119)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:395)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:339)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:748)
at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:486)
at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:411)
at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:338)
at org.apache.struts.chain.commands.servlet.PerformForward.handleAsForward(PerformForward.java:113)
at org.apache.struts.chain.commands.servlet.PerformForward.perform(PerformForward.java:96)
at org.apache.struts.chain.commands.AbstractPerformForward.execute(AbstractPerformForward.java:54)
at org.apache.struts.chain.commands.ActionCommandBase.execute(ActionCommandBase.java:51)
at org.apache.commons.chain.impl.ChainBase.execute(ChainBase.java:190)
at org.apache.commons.chain.generic.LookupCommand.execute(LookupCommand.java:304)
at org.apache.commons.chain.impl.ChainBase.execute(ChainBase.java:190)
at org.apache.struts.chain.ComposableRequestProcessor.process(ComposableRequestProcessor.java:283)
at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1913)
at org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:449)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:620)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
...
Unhandled exception [org.apache.struts.chain.commands.AbstractExceptionHandler] [execute() 95]
org.apache.jasper.JasperException: An exception occurred processing JSP page /login.jsp at line 41
38:
39: <tr>
40: <td align="left"><fmt:message key="login.userName" /></td>
41: <td><label> <html:text property="userName"
42: styleClass="baTextField" styleId="login" />
43: </label></td>
44: </tr>
Stacktrace:
at org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:568)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:470)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:395)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:339)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:748)
at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:486)
at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:411)
at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:338)
at org.apache.struts.chain.commands.servlet.PerformForward.handleAsForward(PerformForward.java:113)
at org.apache.struts.chain.commands.servlet.PerformForward.perform(PerformForward.java:96)
at org.apache.struts.chain.commands.AbstractPerformForward.execute(AbstractPerformForward.java:54)
at org.apache.struts.chain.commands.ActionCommandBase.execute(ActionCommandBase.java:51)
at org.apache.commons.chain.impl.ChainBase.execute(ChainBase.java:190)
at org.apache.commons.chain.generic.LookupCommand.execute(LookupCommand.java:304)
at org.apache.commons.chain.impl.ChainBase.execute(ChainBase.java:190)
at org.apache.struts.chain.ComposableRequestProcessor.process(ComposableRequestProcessor.java:283)
at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1913)
at org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:449)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:620)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208) ..