最简单的jsp+servlet的增删改查代码

package ceet.ac.cn.dao;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

import ceet.ac.cn.model.Admin;

public class AdminDao {
    public List<Admin> getAllAdmin(){  //查询所有信息
        List<Admin> list = new ArrayList<Admin>();  //创建集合
        Connection conn = DbHelper.getConnection();
        String sql  = "select * from admin";  //SQL查询语句
        try {
            PreparedStatement pst = conn.prepareStatement(sql);
            ResultSet rst = pst.executeQuery();
            while (rst.next()) {
                Admin admin = new Admin();
                admin.setId(rst.getInt("id"));  //得到ID
                admin.setUsername(rst.getString("username"));
                admin.setUserpwd(rst.getString("userpwd"));
                list.add(admin);
            }
            rst.close();  //关闭
            pst.close();  //关闭
        } catch (SQLException e) {
            e.printStackTrace();  //抛出异常
        }
        return list;  //返回一个集合
    }
    
    public boolean addAdmin(Admin admin){  //添加信息
        String sql = "INSERT INTO `admin`(`id`,`username`,`userpwd`) VALUES (?,?,?)";  //添加的SQL语句
        Connection conn = DbHelper.getConnection();
        try {
            PreparedStatement pst = conn.prepareStatement(sql);
            pst.setInt(1, admin.getId());
            pst.setString(2, admin.getUsername());
            pst.setString(3, admin.getUserpwd());
            int count = pst.executeUpdate();
            pst.close();
            return count>0?true:false;  //是否添加的判断
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return false;
    }
    
    public boolean updateAdmin(Admin admin){  //修改
        String sql = "UPDATE `admin` SET `username`=?,`userpwd`=? WHERE `id` = ?";  //修改的SQL语句，根据ID修改
        Connection conn = DbHelper.getConnection();
        try {
            PreparedStatement pst = conn.prepareStatement(sql);
            pst.setString(1, admin.getUsername());
            pst.setString(2, admin.getUserpwd());
            pst.setInt(3, admin.getId());  //根据的ID
            int count = pst.executeUpdate();
            pst.close();  //关闭
            return count>0?true:false;  //是否修改的判断
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return false;
    }
    
    public boolean deleteAdmin(int id){  //删除
        String sql = "delete from admin where id = ?";  //删除的SQL语句，根据ID删除
        Connection conn = DbHelper.getConnection();
        try {
            PreparedStatement pst = conn.prepareStatement(sql);
            pst.setInt(1, id);
            int count = pst.executeUpdate();
            pst.close();
            return count>0?true:false;  //是否删除的判断
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return false;
    }
    
    public Admin selectAdminById(int id){  //根据ID进行查询
        Connection conn = DbHelper.getConnection();
        String sql  = "select * from admin where id = "+id;
        Admin admin = null;
        try {
            PreparedStatement pst = conn.prepareStatement(sql);
            ResultSet rst = pst.executeQuery();
            while (rst.next()) {
                admin = new Admin();
                admin.setId(rst.getInt("id"));
                admin.setUsername(rst.getString("username"));
                admin.setUserpwd(rst.getString("userpwd"));
            }
            rst.close();
            pst.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return admin;  //返回
    }
}

package ceet.ac.cn.dao;

import java.sql.Connection;
import java.sql.DriverManager;
/**
 * 连接数据库
 * @author 画船听雨眠
 *
 */
public class DbHelper {
    private static String url = "jdbc:mysql://localhost:3306/admin";  //数据库地址
    private static String userName = "root";  //数据库用户名
    private static String passWord = "359129127";  //数据库密码
    private static Connection conn = null;
    
    private DbHelper(){
        
    }
    
    public static Connection getConnection(){
        if(null == conn){
            try {
                Class.forName("com.mysql.jdbc.Driver");
                conn = DriverManager.getConnection(url, userName, passWord);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        return conn;
    }
    
    public static void main(String[] args) {  //测试数据库是否连通
        System.err.println(getConnection());
    }
}

package ceet.ac.cn.model;

import java.io.Serializable;

public class Admin implements Serializable{  //数据封装类
    
    private static final long serialVersionUID = 1L;
    
    private int id;
    private String username;
    private String userpwd;
    
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getUsername() {
        return username;
    }
    public void setUsername(String username) {
        this.username = username;
    }
    public String getUserpwd() {
        return userpwd;
    }
    public void setUserpwd(String userpwd) {
        this.userpwd = userpwd;
    }
    

}

package ceet.ac.cn.servlet;

import java.io.IOException;

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

import ceet.ac.cn.dao.AdminDao;
import ceet.ac.cn.model.Admin;

public class AddServlet extends HttpServlet{  //添加数据
    private static final long serialVersionUID = 1L;

    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        this.doPost(req, resp);
    }

    protected void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        String username = req.getParameter("username");
        String userpwd = req.getParameter("userpwd");
        Admin admin = new Admin();
        admin.setUsername(new String(username.getBytes("ISO-8859-1"),"UTF-8"));  //转值，中文需要转换为utf-8
        admin.setUserpwd(new String(userpwd.getBytes("ISO-8859-1"),"UTF-8"));
        AdminDao dao = new AdminDao();
        dao.addAdmin(admin);
        req.getRequestDispatcher("ShowServlet").forward(req, resp);
    }    
}

package ceet.ac.cn.servlet;

import java.io.IOException;

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

import ceet.ac.cn.dao.AdminDao;

public class DeleteServlet extends HttpServlet{  //删除数据

    private static final long serialVersionUID = 1L;

    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        this.doPost(req, resp);
    }

    protected void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        String idStr = req.getParameter("id");  //删除数据的ID，根据ID删除
        if(idStr != null && !idStr.equals("")){
            int id = Integer.valueOf(idStr);
            AdminDao dao = new AdminDao();
            dao.deleteAdmin(id);
        }
        req.getRequestDispatcher("ShowServlet").forward(req, resp);
    }
    
    

}

package ceet.ac.cn.servlet;

import java.io.IOException;
import java.util.List;

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

import ceet.ac.cn.dao.AdminDao;
import ceet.ac.cn.model.Admin;

public class ShowServlet  extends HttpServlet{  //显示全部数据

    private static final long serialVersionUID = 1L;

    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        this.doPost(req, resp);
    }

    protected void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        AdminDao dao = new AdminDao();
        List<Admin> list = dao.getAllAdmin();
        req.setAttribute("list", list);
        req.getRequestDispatcher("index.jsp").forward(req, resp);
    }    
}

package ceet.ac.cn.servlet;

import java.io.IOException;

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

import ceet.ac.cn.dao.AdminDao;
import ceet.ac.cn.model.Admin;

public class UpdateServlet extends HttpServlet{  //修改

    private static final long serialVersionUID = 1L;

    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {  //查询到选中ID的值所对应的数据
        String idStr = req.getParameter("id");
        if(idStr != null && !idStr.equals("")){
            int id = Integer.valueOf(idStr);
            AdminDao dao = new AdminDao();
            Admin admin = dao.selectAdminById(id);
            req.setAttribute("admin", admin);
        }
        req.getRequestDispatcher("update.jsp").forward(req, resp);
        
    }

    protected void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {  //根据此ID对数据的值进行修改
        String username = req.getParameter("username");
        String userpwd = req.getParameter("userpwd");
        String idStr = req.getParameter("id");
        Admin admin = new Admin();
        admin.setId(Integer.valueOf(idStr));
        admin.setUsername(new String(username.getBytes("ISO-8859-1"),"UTF-8"));
        admin.setUserpwd(new String(userpwd.getBytes("ISO-8859-1"),"UTF-8"));
        AdminDao dao = new AdminDao();
        dao.updateAdmin(admin);
        req.getRequestDispatcher("ShowServlet").forward(req, resp);
    }
    
    

}

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>    
    <title>添加</title>
    <link rel="stylesheet" href="css/index.css" type="text/css" />
  </head>

  <body>
  <form action="AddServlet" method="post">
    <table border="1" class="t1">
        <tr>
            <td colspan="2"><h1>添加管理员</h1></td>
        </tr>
        <tr>
            <td>管理员帐号:</td>
            <td><input  type="text" name="username"/></td>
        </tr>
        <tr>
            <td>管理员密码:</td>
            <td><input  type="password" name="userpwd"/></td>
        </tr>
        <tr>
            <td colspan="2">
                <input  type="submit" value="提交"/>
                <input  type="reset" value="清空"/>
            </td>
        </tr>
    </table>
   </form>
  </body>
</html>

<%@ page language="java" contentType="text/html; charset=utf-8"
    pageEncoding="utf-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>显示</title>
    <style type="text/css">
            table {
                border: 1px solid pink;
                margin: 0 auto;
            }
            
            td{
                width: 150px;
                border: 1px solid pink;
                text-align: center;
            }
    </style>
</head>
<body>
    <table>
        <tr>
            <td>编号</td>
            <td>帐号</td>
            <td>密码</td>
            <td>操作</td>
        </tr>
        <c:forEach items="${list}" var="item">
            <tr>
                <td>${item.id }</td>
                <td>${item.username }</td>
                <td>${item.userpwd }</td>
                <td><a href="DeleteServlet?id=${item.id }">删除</a>|<a href="UpdateServlet?id=${item.id }">修改</a></td>
            </tr>
        </c:forEach>
        <tr>
            <td colspan="6" style="text-align: left;"><a href="add.jsp">添加管理员</a></td>
        </tr>
    </table>
</body>
</html>

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>    
    <title>修改</title>
    <link rel="stylesheet" href="css/index.css" type="text/css" />
  </head>
  
  <body>
    <form action="UpdateServlet" method="post">
    <table border="1" class="t1">
        <tr>
            <td colspan="2"><h1>修改管理员信息</h1></td>
        </tr>
        <tr>
            <td>编号:</td>
            <td><input  type="text" name="id" value="${admin.id}" readonly="readonly"/></td>
        </tr>
        
        <tr>
            <td>管理员帐号:</td>
            <td><input  type="text" name="username" value="${admin.username}"/></td>
        </tr>
        <tr>
            <td>管理员密码:</td>
            <td><input  type="text" name="userpwd" value="${admin.userpwd}"/></td>
        </tr>
        <tr>
            <td colspan="2">
                <input  type="submit" value="提交"/>
                <input  type="button" value="返回" onclick="history.go(-1)"/>
            </td>
        </tr>
    </table>
   </form>
  </body>
</html>

@CHARSET "UTF-8";
        table.t1 {
            margin-top:10px;
            margin-left:20px;
            margin-right:20px;
            margin-bottom:5px;
            #background-color: #FFF;
            #background:#EEF4F9;
            #border: none;
            border: 1;
            #color:#003755;
            border-collapse:collapse;
            font: 14px  "宋体";
            text-align: center;
        }

        table.t1 th{
                background:#7CB8E2;
                color:#fff;
                padding:6px 4px;
                text-align:center;
        }

        table.t1 td{
                background:#C7DDEE none repeat-x scroll center left;
                color:#000;
                padding:4px 2px;
        }

        table.t1 a{
                text-decoration:none;
                height:1em;
        }

        table.t1 a:link, table.t1  a:visited{
                color:#3366CC;
        }

        table.t1  a:hover{
                color:#B50000;
                text-decoration:underline;
        }