大家帮我看这段代码 错误在哪?
1007 2006-05-06 05:52:19 package online;
import java.io.*;
import java.sql.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class LoginCheck extends HttpServlet
{
private Connection conn=null;
private ResultSet rs =null;
private Statement stmt=null;
public void init() throws ServletException
{
try
{
String host = "localhost";
String db = "db2";
String use = "root";
String pass = "password";
String url = "jdbc:mysql://"+host+":3306/"+db+"?user="+use+"&password="+pass+"&useUnicode=true&characterEncoding=gb2312" ;
Class.forName("org.gjt.mm.mysql.Driver").newInstance();
conn=DriverManager.getConnection(url);
}
catch(Exception e)
{
System.out.println("error:"+e.getMessage());
}
}
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
PrintWriter out = response.getWriter();
String userid = request.getParameter("id");
String userpwd = request.getParameter("password");
try
{
stmt=conn.createStatement();
rs=stmt.executeQuery("select * from member where id='"+userid+"'");
if(rs.next()){
String pwd=rs.getString("passwd").trim();
if(!pwd.equals(userpwd)){
out.println("<script>alert('密码错误');document.location='javascript:history.go(-1);'</script>");
}
else{
out.println("<script>alert('登陆成功');document.location='global_login.jsp'</script>");
}
}
else{
out.println("<script>alert('用户名不存在');document.location='javascript:history.go(-1);'</script>");
}
}
catch(SQLException e)
{
out.println(e.getMessage());
}
finally
{
try
{
rs.close();
stmt.close();
conn.close();
}
catch(SQLException e) {
out.println(e.getMessage());
}
}
}
}
-------------------------------错误提示!-----------------------------
java.lang.NullPointerException
at blog.LoginCheck.doPost(LoginCheck.java:76)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:763)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:856)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:286)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:256)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:151)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:562)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:974)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:205)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:151)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:562)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:974)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:177)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:151)
at org.apache.catalina.valves.ErrorDispatcherValve.invoke(ErrorDispatcherValve.java:171)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:149)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:172)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:149)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:562)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:974)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:156)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:151)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:562)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:974)
at org.apache.coyote.tomcat5.CoyoteAdapter.service(CoyoteAdapter.java:203)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:637)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:488)
at org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:568)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:631)
at java.lang.Thread.run(Unknown Source)