Question

查看时，查看页面来源显示所有数据。在网页上，它不会呈现完整数据。还有一个当我点击删除时它会显示我是学习Java Servlet的新手，也是编程语言的新手。我不知道我做错了什么？我不知道如何防止查询字符串获得不必要的值。有人可以帮我这个吗？

<pre><code>
package com.jspiders.studentsapp.servlets;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;



import com.mysql.jdbc.Driver;





public class Viewallstudentdelete extends HttpServlet
{
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException 
    {
            resp.setContentType("text/html");
            PrintWriter out=resp.getWriter();

    System.out.println("mime type set");

        Connection con = null;
        ResultSet rs = null;
        Statement stmt = null;

        try {
            Driver driverref = new Driver();
            DriverManager.registerDriver(driverref);
            String dburl = "jdbc:mysql://localhost:3306/Becm145_DB?user=root&password=root";
            con = DriverManager.getConnection(dburl);

            String query = "select * from students_info si,students_otherinfo so,guardian_info gi"
                    + " where si.regno=so.regno and so.regno=gi.regno";

            stmt = con.createStatement();
            rs = stmt.executeQuery(query);

             out.println("<html>"

                        + "<body>"

                 + "<table border=\"1\"width=\"100%\" >"
                 +"<tr ><th>Regno</th><th>First Name</th><th>Middle Name</th><th>Last Name</th><th>Is Admin</th><th>Password</th><th>Gfirst Name</th><th>Gmiddle Name</th><th>GLast Name</th><th>Delete</th> </tr>");
             while(rs.next()) 
            {

                int regno=rs.getInt("regno");//Integer.parseInt(req.getParameter("regno"));
                String fnm=rs.getString("firstname");
                   String mnm=rs.getString("middlename");
                   String lnm=rs.getString("lastname");
                   String admin=rs.getString("isadmin");
                   String passw=rs.getString("password");
                   String gfnm=rs.getString("gfirstname");
                   String gmnm=rs.getString("gmiddlename");
                   String glnm=rs.getString("glastname");
                    out.println("<tr><td>"  
                             + regno
                             +"</td><td>"
                             + fnm
                             +"</td><td> "
                             +mnm
                             +"</td><td>"
                             +lnm
                             +"</td><td>"
                             +admin
                             +"</td><td>"
                             +passw
                             +"</td><td>"
                             +gfnm
                             +"</td><td>"
                             +gmnm
                             +"</td><td>"
                             +glnm
                             +"</td><td>"
                             +"<a href=\"./deleteservlet?regno="
                             +regno
                             +" >Delete</a></td></tr>");






                    }
            out.print("</table>"
                 +"</body>"     
                 +"</html>");
        } catch (Exception e) {
            e.printStackTrace();

        } finally {
            System.out.println("close all jdbc objects");
        }

        try {
            if (con != null) {
                con.close();
            }
            if (stmt != null) {
                stmt.close();

            }
            if (rs != null) {
                rs.close();

            }
        }

        catch (SQLException e) {
            e.printStackTrace();
        }

    }

    }

</pre></code>



package com.jspiders.studentsapp.servlets;

import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.PreparedStatement;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.mysql.jdbc.Driver;
public class Deleteservlet extends HttpServlet
{
        protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException     {
                resp.setContentType("text/html");
                PrintWriter out=resp.getWriter();
                int regno=Integer.parseInt(req.getParameter("regno"));

        System.out.println("mime type set");

            Connection con = null;
            ResultSet rs = null;
            PreparedStatement pstmt = null;
            PreparedStatement pstmt1 = null;
            PreparedStatement pstmt2 = null;
            int count,count1,count2 =0;
            try {
                Driver driverref = new Driver();
                DriverManager.registerDriver(driverref);
                String dburl = "jdbc:mysql://localhost:3306/Becm145_DB?user=root&password=root";
                con = DriverManager.getConnection(dburl);

                String query = "delete from students_info  where regno=?";



              String query1 =   "delete from students_otherinfo  where regno=? ";
              String query2=" delete from guardian_info  where regno=? ";//garbage collector call finalize before garbage collected when the space is full or reach level at that time garbage call finalize and then collected

                pstmt = con.prepareStatement(query);
                pstmt.setInt(1,regno);
                 count = pstmt.executeUpdate();
                pstmt1 = con.prepareStatement(query1);
                pstmt1.setInt(1,regno);
                count1 = pstmt1.executeUpdate();
                pstmt2 = con.prepareStatement(query2);
                pstmt2.setInt(1,regno);
                count2 = pstmt2.executeUpdate();
                if(count == 1 && count1 == 1 && count2 == 1)
                {
                    out.println("<h1>profile ,is deleted</h1>");
                }
                else
                {
                    out.println("<h1>failed in deleting profile</h1>");   
                }

            } catch (Exception e) {
                e.printStackTrace();

            } finally {
                System.out.println("close all jdbc objects");
            }

            try {
                if (con != null) {
                    con.close();
                }
                if (pstmt != null) {
                    pstmt.close();

                }
                if (rs != null) {
                    rs.close();

                }
            }

            catch (SQLException e) {
                e.printStackTrace();
            }

        }

        }

客户端数据未显示在网页上？

0 个答案: