jsp求大神修改代码，servlet连数据库

Question

package my.servlets;
import java.io.*;
import my.model.mess;
import java.sql.*;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;

import db.DBConnAccess;
/**

• Servlet implementation class tt
  */
  public class tt extends HttpServlet {
  private static final long serialVersionUID = 1L;

  /**

  • @see HttpServlet#HttpServlet() */ public tt() { super(); // TODO Auto-generated constructor stub }

  /**

  • @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response) */ protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub this.doPost(request, response); }

  /**

  • @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
    */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    // TODO Auto-generated method stub

    String email=request.getParameter("email");
    String login=request.getParameter("login");
    String password=request.getParameter("password");
    String confirmpass=request.getParameter("confirmpass");
    //创建session周期的RegInfo对象存储出错的信息
    mess regInfo=new mess();
    HttpSession session=request.getSession();
    session.setAttribute("regInfo",regInfo);
    
    PrintWriter out=response.getWriter();
    if(email==null || login.equals("") || password==null || confirmpass.equals("")){
    regInfo.setMess("不能为空！");
    response.sendRedirect("signup.jsp");

            return;
        }
    
        if(!password.equals(confirmpass)){
            regInfo.setMess("两次输入的密码不一致！");
            response.sendRedirect("signup.jsp");
    
            return;
        }
        DBConnAccess DBConn=new DBConnAccess();
        String dbpath = "test.mdb"; // 
        Connection conn = DBConn.getConnToAccess(request.getSession().getServletContext().getRealPath(dbpath)); 
    
        Statement stmt=null;
        ResultSet rs = null; 
    
        try {
            stmt = conn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_READ_ONLY);
            String sql = "insert into username(email,login,pwd)values('"+email+"','"+login+"','"+password+"')";
            rs = stmt.executeQuery(sql); 
            String selectsql="select *from username";
            ResultSet rs1 = stmt.executeQuery(selectsql);
            while (rs1.next()) { 
                out.println(rs.getString("login"));
                } 
        } catch (Exception e) {
            // TODO Auto-generated catch block
            out.println(e);
            e.printStackTrace();
        } 
    
            DBConn.close(); 
    
        //regInfo.setMess("");
        //验证成功调用ProcessData对象的update方法将注册信息添加入数据库
    
        //regInfo.setMess("注册成功，请重新登录！");
        //response.sendRedirect("signin.jsp");
        //RequestDispatcher requestDispatcher=request.getRequestDispatcher("signin.jsp");
        //requestDispatcher.forward(request, response);
    

  }

}
异常：java.sql.SQLException: No ResultSet was produced

Answer 1

rs = stmt.executeQuery(sql);
String selectsql="select *from username";
ResultSet rs1 = stmt.executeQuery(selectsql);
你处理了两次sql语句，只用了一次 stmt = conn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_READ_ONLY);
你在处理String selectsql语句后再添加一次conn.createStatement连接试试看，然后再做ResultSet rs1 = stmt.executeQuery(selectsql);语句，毕竟是做两次不同的sql操作，两次访问数据库，不一定对，试试看