学了几个月java ,头一次被整的要疯掉了。解决办法

package  com.nong;import javax.servlet.*;import javax.servlet.http.*;import java.io.*;import java.util.*;import java.sql.*;public class LoginCL extends HttpServlet{public void doGet(HttpServletRequest req,HttpServletResponse res)throws ServletException,IOException{      String u=req.getParameter("username");    String p=req.getParameter("passwd");    //UserBeanCL  ubc=new UserBeanCL();    ConDB db=new ConDB();    db.closeall();//为了确保上一次没有断开的连接断开    if(db.isExist("select * from users"))    {                   res.setContentType("text/html;charset=gbk");        PrintWriter pw=res.getWriter();        ConDB db1=new ConDB();                try{            ResultSet rs1=db1.getRset("select * from student");            while(rs1.next())            {            pw.println("aa");            }                                       try{                rs1.close();                  }               catch(Exception e)               {e.printStackTrace();}        }                catch(Exception e)        {            e.printStackTrace();                }        db1.closeall();        db.closeall();                                                                    /*                                        Cookie name=new Cookie("myname",u);        Cookie pass=new Cookie("mypasswd",p);        name.setMaxAge(14*24*3600);        pass.setMaxAge(14*24*3600);        res.addCookie(name);        res.addCookie(pass);                HttpSession hs=req.getSession(true);        hs.setMaxInactiveInterval(14*24*3600);        hs.setAttribute("myname",u);        hs.setAttribute("mypasswd",p);                        HttpSession hh=req.getSession(false);        pw.println("你好"+(String)hh.getAttribute("myname"));                int pageSize=2;        int pageNow=1;        UserBeanCL ubb=new UserBeanCL();                        ArrayList al=ubb.getResultBypage(pageNow,pageSize);        pw.println(al.size());                                pw.println("<table border=1>");        pw.println("<tr><th>id</th><th>name</th><th>age</th><th>score</th></tr>");        for(int i=0;i<al.size();i++)        {              UserBean ub=(UserBean)al.get(i);            pw.println("<tr>");            pw.println("<td>"+ub.getID()+"</td>");            pw.println("<td>"+ub.getName()+"</td>");            pw.println("<td>"+ub.getAge()+"</td>");            pw.println("<td>"+ub.getScore()+"</td>");            pw.println("</tr>");                    }        pw.println("</table>");            */        }    else    {                  res.sendRedirect("http://www.baidu.com");        }}public void doPost(HttpServletRequest req,HttpServletResponse res)throws ServletException,IOException{    this.doGet(req,res);}    }

package com.nong;import java.sql.*;public class ConDB {private Connection ct=null;private PreparedStatement pm=null;private ResultSet rs=null;public Connection getConn(){    try    {        Class.forName("com.microsoft.jdbc.sqlserver.SQLServerDriver");        ct=DriverManager.getConnection("jdbc:microsoft:sqlserver://127.0.0.1:1434;DatabaseName=Mybase","sa","long");    }    catch(Exception e)    {e.printStackTrace();}    return ct;}public ResultSet getRset(String sqlstr){     try    {           ct=getConn();        pm=ct.prepareStatement(sqlstr);        rs=pm.executeQuery();            }   catch(Exception e)       {e.printStackTrace();}         finally   {    return rs;   }}public boolean isExist(String strsql){    boolean  b=false;    try    {    ct=this.getConn();    pm=ct.prepareStatement(strsql);    rs=pm.executeQuery();      if(rs.next())      {        b=true;         }    }    catch(Exception ex)    {        ex.printStackTrace();    }    finally    {            return b;    }    }public void closeall(){ try{  if(this.rs!=null){rs.close();this.rs=null;}  if(this.pm!=null){pm.close();this.pm=null;}  if(this.ct!=null){ct.close();this.ct=null;}}catch(Exception e){e.printStackTrace();}}   }