不知道为什么出现错误，求解决

Question

HTTP Status 500 - An exception occurred processing JSP page /index.jsp at line 33type Exception reportmessage An exception occurred processing JSP page /index.jsp at line 33description The server encountered an internal error that prevented it from fulfilling this request.exception org.apache.jasper.JasperException: An exception occurred processing JSP page /index.jsp at line 33 30:      <tr> 31:       <%  32:        ItemsDao action=new ItemsDao(); 33:        Item item=action.getItemById(Integer.parseInt(request.getParameter("id"))); 34:        if(item!=null) 35:        { 36:       %> Stacktrace: org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:568) org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:470) org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:395) org.apache.jasper.servlet.JspServlet.service(JspServlet.java:339) javax.servlet.http.HttpServlet.service(HttpServlet.java:727) org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)root cause java.lang.NumberFormatException: null java.lang.Integer.parseInt(Unknown Source) java.lang.Integer.parseInt(Unknown Source) org.apache.jsp.index_jsp._jspService(index_jsp.java:101) org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70) javax.servlet.http.HttpServlet.service(HttpServlet.java:727) org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432) org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:395) org.apache.jasper.servlet.JspServlet.service(JspServlet.java:339) javax.servlet.http.HttpServlet.service(HttpServlet.java:727) org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)note The full stack trace of the root cause is available in the Apache Tomcat/7.0.56 logs.Apache Tomcat/7.0.56

Answer 1

很明显啊 java.lang.NumberFormatException 空指针异常