java.lang.NullPointerException异常
<%@ page language= "java " pageEncoding= "GBK " %>
<%@ include file= "../../common.jsp " %>
<LINK href=../../css/css.css rel=stylesheet>
<style type= "text/css ">
<!--
.STYLE1 {font-family: Verdana, Arial, Helvetica, sans-serif}
-->
</style>
<link href= "../css/css.css " rel= "stylesheet " type= "text/css ">
<body bgcolor= "#F4F2F2 " topmargin= "4 ">
<br/>
<% Database dsm=new Database();
ResultSet rs=null;
int N_id=0;
String USER_name= " ";
String sqlStr= " ";
String N_sign= " ";
String N_addDate= " ";
String N_addUser= " ";
String N_title= " ";
String N_content= " ";
String N_sort= " ";
String S_id= " ";
String P_id= " ";
%>
<%
N_id=3;
System.out.println(N_id);
USER_name=(String)session.getAttribute( "USER_name ");
sqlStr= "select * from newsshow where N_id=3 ";
//System.out.println(sqlStr);
try{
dsm.setSqlStr(sqlStr);
dsm.executeQuery();
rs=dsm.getRs();
while(rs.next()){
N_title=rs.getString( "N_title ");
N_content=rs.getString( "N_content ");
N_addDate=(rs.getString( "N_addDate ")).substring(0,19);
N_addUser=rs.getString( "N_addUser ");
N_sort=rs.getString( "S_name ");
N_sign=rs.getString( "P_name ");
%>
<form method= "POST " name= "myform " action= "../../servlet/SortAdd ">
<table width= "700 " height= "127 " border= "0 " align= "center "
cellpadding= "0 " cellspacing= "1 " bgcolor= "#BBB3AA ">
<tr bgcolor= "FBF5F0 ">
<td height= "30 " colspan= "4 " align= "center "> <font color= "#CC0000 "> <b> 新闻类别信息修改
</b> </font> </td>
</tr>
<tr bgcolor= "#FFFFFF ">
<td width= "89 " height= "25 " align= "center ">
<font face= "Verdana, Arial, Helvetica, sans-serif ">
新闻标题： </font> </td>
<td colspan= "3 ">
<input name= "title " type= "text " id= "title " size= "55 " value= " <%=N_title %> "> </td>
</tr>
<tr bgcolor= "#FFFFFF ">
<td height= "25 " align= "center "> 新闻类型： </td>
<td width= "234 " height= "20 " align= "left " >
<input name= "N_sort " type= "text " id= "N_sort " value= " <%=N_sort %> " size= "20 ">
<input type= "button " name= "editsort " value= "更改 " onClick= "window.location= 'sortselect2.jsp ' "> </td>
<td width= "97 " align= "center "> 添加时间： </td>
<td width= "275 " align= "left "> <%=N_addDate %> </td>
</tr>
<tr bgcolor= "#FFFFFF ">
<td height= "25 " align= "center "> 针对省份： </td>
<td height= "20 " align= "left ">
<%
P_id=(null==request.getParameter( "P_id ")? "00 ":request.getParameter( "P_id "));
System.out.println(P_id);
if(!P_id.equals( "00 ")){
ResultSet rs3=null;
String sql3= "select * from tb_pro where P_id= ' "+P_id+ " ' ";
try{
dsm.setSqlStr(sql3);
dsm.executeQuery();
System.out.println(sql3);
rs3=dsm.getRs();
while(rs3.next()){
N_sign=rs.getString( "P_name ");
System.out.println( "== "+N_sign);
session.setAttribute( "P_id ",P_id);
}
System.out.println(N_sign);
}
catch(Exception ee){}
}
%>
<input name= "N_sign " type= "text " id= "N_sign " value= " <%=N_sign %> " size= "20 ">
<input type= "button " name= "editpro " value= "更改 " onClick= "window.location= 'proselect.jsp ' "> </td>
<td width= "97 " height= "20 " align= "center "> 添加作者： </td>
<td height= "20 " align= "left "> <%=N_addUser %> </td>
</tr>
<tr bgcolor= "#FFFFFF ">
<td height= "20 " align= "center "> 新闻内容： </td>
<td height= "20 " colspan= "3 " align= "left "> <input type= "hidden " name= "content " value= " <%=N_content %> "> <iframe src= '../../eWebEditor/ewebeditor.htm?id=content ' frameborder=0 scrolling=no width= '550 ' HEIGHT= '350 '> </iframe> </td>
</tr>
<tr bgcolor= "#FFFFFF ">
<td height= "30 " colspan= "4 " align= "right "> <span class= "STYLE1 ">
<input type= "submit " name= "Submit2 " value= "添加 ">
<input type= "reset " name= "Submit " value= "重置 ">
<input type= "button " name= "Submit3 " value= "返回 " onClick= "javascript:history.go(-1); ">
</span> </td>
</tr>
</table>
<%}}catch(Exception ew){System.out.println(ew.toString());} %>
</form>
上面是我的JSP页面代码
00
3
4
select * from tb_pro where P_id= '4 '
java.lang.NullPointerException
这是在控制台输出的结果
在传一个值过来后，能接到，也能执行SQL查询，但是一到rs（N_sign=rs.getString( "P_name ");）那里就走不下去了
哪位高手知道错误原因啊，帮帮忙！谢谢了！
[解决办法]
写错了吧，N_sign=rs3.getString( "P_name ");应该是rs3啊，还有把这些操作封装下吧，别把java代码和jsp页面耦合在一起，查错误很麻烦，最好分层
[解决办法]
N_sign=rs.getString( "P_name ");
这一句改为：
N_sign=rs3.getString( "P_name ");
