请问如何解决这种异常报错的呢？

Question

type Exception reportmessage 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:372)
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 java.lang.NullPointerException
org.apache.jsp.reg_jsp._jspService(reg_jsp.java:84)
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)

Answer 1

我的代码是这样子的，不知哪里出问题了，请各位帮忙看看，谢谢咯
<%@page contentType="text/html; charset=gbk" %>
<%@page language="java" import="java.sql.*" %>
<% 
request.setCharacterEncoding("GBK");
String Username,Password,Phone,Addr;
Username=request.getParameter("username");
Password=request.getParameter("password");
Phone=request.getParameter("phone");
Addr=request.getParameter("addr");

String insertquery="insert into user1 set username = '" + Username + "',password = '" + Password +"',phone = '" + Phone + "',addr = '" + Addr + "'";
String selectquery="select * from user1 where username = '" +Username +"'";

Connection conn = null;
Statement stmt = null;
ResultSet rs = null;
try
{
Class.forName("com.mysql.jdbc.Driver").newInstance();
conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/shopping?user=mscc&password=123456");
stmt = conn.createStatement();
rs = stmt.executeQuery(selectquery);

if(rs.next())
{
response.sendRedirect("reg.htm");
return;
}
else
{
stmt.executeUpdate("insertquery");
}

}
catch(SQLException ex)
{
ex.printStackTrace();
response.sendRedirect("reg.htm");
}
finally
{
stmt.close();
conn.close();
}
session.setAttribute("username",Username);
response.sendRedirect("regsuc.jsp");
 %>

Answer 2

取的页面传参的值，还有记录的值，取到后应一律验证是否是NULL

Answer 3

楼主你的插入语句有有问题
String insertquery=" insert into user1 values ('"+Username+"' , '"+password+"' , '"+Phone+"' , '"+Addr+"' ) "

Answer 4

要不，你把项目传给我，[email protected]

Answer 5

<%@page contentType="text/html; charset=gbk" %>
<%@page language="java" import="java.sql.*" %>
<%  
request.setCharacterEncoding("GBK");
String Username,Password,Phone,Addr;
Username=request.getParameter("username");
Password=request.getParameter("password");
Phone=request.getParameter("phone");
Addr=request.getParameter("addr");String insertquery="insert into user1 set username = '" + Username + "',password = '" + Password +"',phone = '" + Phone + "',addr = '" + Addr + "'";
String selectquery="select * from user1 where username = '" +Username +"'";Connection conn = null;
Statement stmt = null;
ResultSet rs = null;
try
{ 
Class.forName("com.mysql.jdbc.Driver").newInstance();
conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/shopping?user=mscc&password=123456");
stmt = conn.createStatement();
rs = stmt.executeQuery(selectquery);if(rs.next())
{
response.sendRedirect("reg.htm");
return;
}
else
{
stmt.executeUpdate(insertquery);
}}
catch(SQLException ex)
{response.sendRedirect("reg.htm");
ex.printStackTrace();}
finally
{
rs.close();
stmt.close();
conn.close();
}
session.setAttribute("username",Username);
response.sendRedirect("regsuc.jsp");
 %>我把你的代码了一下，就ok了！stmt.executeUpdate("insertquery");
这句话改了stmt.executeUpdate(insertquery);lz粗心啊！1

Answer 6

取的页面传参的值，还有记录的值，取到后应一律验证是否是NULL