form中的action问题！

bengan 2004-05-08 10:31:18

我写以下代码：
<%@ page contentType="text/html; charset=gb2312" language="java" import="java.sql.*" errorPage="" %>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<jsp:useBean id="mysqlCon" scope="page" class="db.mysqlConn"/>
<title>无标题文档</title>
</head>

<body>
<%
String ss=request.getParameter("ss");
out.print(ss);
String type=request.getParameter("type");
if(type.equals("big")){
out.print("添加大类");
%>
<form action="add.jsp">
<input name="ss" type="submit" value="提交">
</form>
<%
}
if(type.equals("ok"))
out.print("type=ok");
%>
</body>
</html>
第一次进入没问题。但点激“提交”按钮有以下出错提示：
HTTP Status 500 -

--------------------------------------------------------------------------------

type Exception report

message

description The server encountered an internal error () that prevented it from fulfilling this request.

exception

org.apache.jasper.JasperException
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:358)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:301)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:248)
javax.servlet.http.HttpServlet.service(HttpServlet.java:856)

root cause

java.lang.NullPointerException
org.apache.jsp.tp.add_jsp._jspService(add_jsp.java:64)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:133)
javax.servlet.http.HttpServlet.service(HttpServlet.java:856)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:311)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:301)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:248)
javax.servlet.http.HttpServlet.service(HttpServlet.java:856)

note The full stack trace of the root cause is available in the Tomcat logs.

--------------------------------------------------------------------------------

Apache Tomcat/5.0.19

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Dog2Cat 2004-05-08

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问题出在：
<form action="add.jsp">
<input name="ss" type="submit" value="提交">
</form>
本页面（ADD.JSP)开始有接受表单项的语句：
String ss=request.getParameter("ss");
String type=request.getParameter("type");
但ADD.JSP页中的表单提交到本页时没有对应的表单项，故出错。
修改：
将ADD.JSP的表改为：
<form action="add.jsp">

<input name="ss" type="hidden" value=<%=ss%>>
<input name="type" type="hidden" value=<%=type%>>

<input name="ss" type="submit" value="提交">
</form>

bengan 2004-05-08