modifyuser.java

jsp编的图书管理系统。请大家多多指教啊！ 服务器用tomcat！

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;
import java.sql.*;
import data.LoginData;
public class ModifyUser extends HttpServlet{
	private static final String CONTENT_TYPE="text/html;charset=GBK";
	public void doPost(HttpServletRequest request,HttpServletResponse response)
	throws ServletException,IOException{
		String strSql=null;
		String stautes=null;
		ResultSet rs=null;
		Statement stmt=null;
		int result=0;
		request.setCharacterEncoding("GBK");
		String oldusername = request.getParameter("oldusername");
		String oldpassword = request.getParameter("oldpassword");
		String  newpassword =request.getParameter("newpassword");
		LoginData loginData = new LoginData();
		Connection conn = loginData.getConn();
        HttpSession session =request.getSession(false);
        if(session==null)
        {
         response.sendRedirect("tushu/error.jsp");
         return;
        }
         session.setAttribute("User",oldusername);
         
         
		 try{
			 stmt = conn.createStatement();
             strSql="SELECT * FROM Reader WHERE Rpassword='"+oldpassword+"'"+" "+"AND"+" "+"Rnumber='"+oldusername+"'";
			  rs = stmt.executeQuery(strSql);
			 if(rs.next()){
			 	   strSql="UPDATE Reader SET Rpassword='"+newpassword+"'"+" "+"WHERE Rnumber='"+oldusername+"'";
			       result=stmt.executeUpdate(strSql);
			   	  if(result==1){
			   	  	      stautes ="修改成功!";
			   	  	      session.setAttribute("Pass",newpassword);
			   	  	      session.setAttribute("Modify",stautes);
			   		   	  response.sendRedirect("tushu/Modify_Success.jsp");
			   		     }
			   		else
			   		  {       stautes ="修改失败,系统问题,请下次修改!";
			   		  	     session.setAttribute("Modify",stautes);
			   		    	response.sendRedirect("tushu/Modify_Success.jsp");	
			   		  }
			    }
			 	else{
			 	     stautes ="修改失败,你的上次用老密码或老的用户名不正确!";
			   		 session.setAttribute("Modify",stautes);
			 		response.sendRedirect("tushu/Modify_Success.jsp");
			 		}
		   }catch(Exception ex){
		   	ex.printStackTrace();
		   	}
		
		}
		public void destroy(){
			}
	
	}