使用Servlet+JSP实现学生管理系统

Posted 2021-09-07 SmallCuteMonkey

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文章目录

使用Servlet+JSP实现学生管理系统

使用Servlet+JSP实现学生管理系统

eg1: 使用servlet来实现登录功能

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<h1>登录页面</h1>
<!--前端访问后台资源 不加/-->
<form action="login" method="post">

    用户名: <input type="text" name="username"><br/>
    密码： <input type="password" name="password"><br/>
    爱好： <input type="checkbox" name="love" value="1">学习
    <input type="checkbox" name="love" value="2">篮球
    <input type="checkbox" name="love" value="3">游戏<br/>
    <input type="submit" value="登录">
</form>
</body>
</html>

LoginServlet:

package com.jishou.servlet;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@WebServlet(name = "LoginServlet",urlPatterns = "/login")
public class LoginServlet extends HttpServlet {

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("post请求。。。。。");
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        System.out.println("get请求。。。。");
    }
}

登录逻辑里面取前台用户输入的参数：

@WebServlet(name = "LoginServlet",urlPatterns = "/login")
public class LoginServlet extends HttpServlet {

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request,response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        //登录的处理逻辑
        //1. 取前台表单的参数  request
        /*
        	public String getParameter(String name)					  返回指定name对应的参数的值

	public String[] getParameterValues(String name)		返回指定name对应的一组参数值，返回值是数组

	public Enumeration getParameterNames()  				 返回所有客户请求的参数名
         */

        //2. 登录处理
        //参数名必须和前台表单name属性值一致
        request.setCharacterEncoding("utf-8");//设置请求编码 放在第一行
        String username = request.getParameter("username");//取用户名
        String password = request.getParameter("password");//取密码
        String[] loves = request.getParameterValues("love");//取爱好

        System.out.println("用户名： "+username+" 密码："+password);
        if(loves!=null&&loves.length>0){
            for(String love: loves){
                System.out.println("爱好： "+love);
            }
        }

        //3. 产生响应 成功或者失败
        //通过response响应对象输出内容到浏览器里面
        response.setCharacterEncoding("utf-8");
        response.setContentType("text/html");//说明以html方式来响应
        PrintWriter out = response.getWriter();//获取字符输出流
        out.println("用户名是："+username+"密码是： "+password);
        out.flush();//刷新流
        out.close();//关闭流
    }
}

url访问：

http://localhost:8080/servlet02_2_war_exploded/login.html

eg2: 使用servlet来实现登录功能

1.创建数据库表 mysql

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2.创建web project

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3. 在web目录下创建登录页面 login.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<h1>登录页面</h1>
<!--前端访问后台资源 不加/-->
<form action="login" method="post">

    用户名: <input type="text" name="username"><br/>
    密码： <input type="password" name="password"><br/>

    <input type="submit" value="登录">
</form>
</body>
</html>

4.编写实体类User

package com.jishou.pojo;

public class User {

    private int id;
    private String username;
    private String password;

    public User() {
    }

    public User(int id, String username, String password) {
        this.id = id;
        this.username = username;
        this.password = password;
    }

    public User(String username, String password) {
        this.username = username;
        this.password = password;
    }

    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 getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\\'' +
                ", password='" + password + '\\'' +
                '}';
    }
}

5.编写数据访问层 UserDao接口和接口实现类

导入mysql依赖，复制到web–web-inf下的lib目录底下：

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注意： web项目中mysql依赖包必须复制到web-inf下面的lib目录里面

吧mysql依赖引入到该工程里面

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数据库连接工具类 DBUtil

package com.jishou.util;

import java.sql.*;


public class DBUtil {

    private  static String driverClassName="com.mysql.jdbc.Driver";
    private  static String url="jdbc:mysql://localhost:3306/test?characterEncoding=utf8";
    private  static String username="root";
    private  static String password="123456";

    static{

        try {
            Class.forName(driverClassName);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }

    public static Connection getConnection(){
        try {
            return DriverManager.getConnection(url, username, password);
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }
        return  null;
    }

    public static void close(Connection conn, PreparedStatement pstmt, ResultSet rs){
       try {
           if (rs != null) {
               rs.close();
           }
           if (pstmt != null) {
               pstmt.close();
           }
           if (conn != null) {
               conn.close();

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

    public static void close(Connection conn, PreparedStatement pstmt){
        try {

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

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

UserDao

package com.jishou.dao;

import com.jishou.pojo.User;

public interface UserDao {

    public User queryOneUser(User user) ;

    public int insertUser(User user);
}

UserDaoImpl

package com.jishou.dao;

import com.jishou.pojo.User;
import com.jishou.util.DBUtil;

import java.sql.*;

public class UserDaoImpl implements UserDao{

    /*@Override
    public User queryOneUser(User user) throws SQLException, ClassNotFoundException {
        //1.加载驱动      建厂
        String driverClassName="com.mysql.jdbc.Driver";
        String url="jdbc://mysql:localhost:3306/test?characterEncoding=utf8";
        String username="root";
        String password="123456";

        String sql="select * from user where username=? and password=?";

        User u=null;

        Class.forName(driverClassName);
        //2.获取连接      修路
        Connection conn = DriverManager.getConnection(url, username, password);
        //3.创建PreparedStatement    造车
        PreparedStatement pstmt = conn.prepareStatement(sql);
        pstmt.setString(1,user.getUsername());
        pstmt.setString(2,user.getPassword());
        //4.执行操作    拉货
        ResultSet rs = pstmt.executeQuery();
        //5.处理结果集  查询会有结果集 增删改 没有    处理货物
        if(rs.next()){
            int id = rs.getInt(1);
            String name = rs.getString(2);
            String pass = rs.getString(3);

            u=new User(id,name,pass);
        }
        //6. 关闭资源    路 砸了   货物 毁了 车 砸了
        if(rs!=null){
            rs.close();
        }
        if(pstmt!=null){
            pstmt.close();
        }
        if(conn!=null){
            conn.close();

        }
        return u;
    }*/

    public User queryOneUser(User user)  {
        //1.加载驱动      建厂
        String sql="select * from user where username=? and password=?";

        User u=null;
        Connection conn=null;
        PreparedStatement pstmt=null;
        ResultSet rs=null;

        try {
            //2.获取连接      修路

            conn= DBUtil.getConnection();
            //3.创建PreparedStatement    造车
            pstmt = conn.prepareStatement(sql);
            pstmt.setString(1, user.getUsername());
            pstmt.setString(2, user.getPassword());
            //4.执行操作    拉货
            rs = pstmt.executeQuery();
            //5.处理结果集  查询会有结果集 增删改 没有    处理货物
            if (rs.next()) {
                int id = rs.getInt(1);
                String name = rs.getString(2);
                String pass = rs.getString(3);

                u = new User(id, name, pass);
            }
        }catch (SQLException e){
            e.printStackTrace();
        }
        //6. 关闭资源    路 砸了   货物 毁了 车 砸了
        DBUtil.close(conn,pstmt,rs);
        return u;
    }

    @Override
    public int insertUser(User user) {
        return 0;
    }
}

6.编写service层接口和实现类

UserService

package com.jishou.service;

import com.jishou.pojo.User;

public interface UserService {

    //登录
    public User login(User user);
    //注册
    public boolean register(User user);
}

UserServiceImpl

package com.jishou.service;

import com.jishou.dao.UserDao;
import com.jishou.dao.UserDaoImpl;
import com.jishou.pojo.User;

public class UserServiceImpl  implements UserService{

    private  UserDao userDao=new UserDaoImpl();

    @Override
    public User login(User user) {
        return userDao.queryOneUser(user);
    }

    @Override
    public boolean register(User user) {
        return false;
    }
}

7.编写Servlet的登录实现逻辑

LoginServlet

package com.jishou.servlet;

import com.jishou.pojo.User;
import com.jishou.service.UserService;
import com.jishou.service.UserServiceImpl;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;

@WebServlet(name = "LoginServlet",urlPatterns = "/login")
public class LoginServlet extends HttpServlet {

    private UserService userService=new UserServiceImpl();

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        //1. 取参数
        request.setCharacterEncoding("utf-8");
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        User qtUser=new User(username,password);
        //连数据库查询
        User htUser = userService.login(qtUser);
        //响应
        response.setCharacterEncoding("utf-8");
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        //判断是否登录成功
        if(htUser!=null){
            out.println("<h1>登录成功</h1>");
        }else{
            out.println("<h1>登录失败</h1>");
        }
        out.flush();
        out.close();
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request, response);
    }
}

8.浏览器url访问登录页面，展示运行效果

http://localhost:8080/stuManage_02_war_exploded/login.html

正常jdbc流程：

 public User queryOneUser(User user) throws SQLException, ClassNotFoundException {
        //1.加载驱动      建厂
        String driverClassName="com.mysql.jdbc.Driver";
        String url="jdbc://mysql:localhost:3306/test?characterEncoding=utf8";
        String username="root";
        String password="123456";

        String sql="select * from user where username=? and password=?";

        User u=null;

        Class.forName(driverClassName);
        //2.获取连接      修路
        Connection conn = DriverManager.getConnection(url, username, password);
        //3.创建PreparedStatement    造车
        PreparedStatement pstmt = conn.prepareStatement(sql);
        pstmt.setString(1,user.getUsername());
        pstmt.setString(2,user.getPassword());
        //4.执行操作    拉货
        ResultSet rs = pstmt.executeQuery();
        //5.处理结果集  查询会有结果集 增删改 没有    处理货物
        if(rs.next()){
            int id = rs.getInt(1);
            String name = rs.getString(2);
            String pass = rs.getString(3);

            u=new User(id,name,pass);
        }
        //6. 关闭资源    路 砸了   货物 毁了 车 砸了
         if(rs!=null){
            rs.close();
        }
        if(pstmt!=null){
            pstmt.close();
        }
        if(conn!=null){
            conn.close();
           
        }
        return u;
    }

eg3: 使用Servlet实现注册功能

在web目录下新建register.html文件

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

<h1>注册页面</h1>

<!--前端访问路径都不加/ -->
<form action="register" method="post">
    用户名： <input type="text" name="username"><br>
    密码： <input type="password" name="password"><br>
    <input type="submit" value="注册">
</form>
</body>
</html>

编写数据访问层UserDao和实现类里面的注册逻辑

UserDao接口

 public int insertUser(User user);

UserDaoImpl接口实现类

  @Override
    public int insertUser(User user) {

        String sql="INSERT INTO user (username, password) VALUES ( ?, ?)";
        Connection conn = DBUtil.getConnection();
        PreparedStatement pstmt=null;
        int row=0;
        try {
            pstmt = conn.prepareStatement(sql);
            pstmt.setString(1, user.getUsername());
            pstmt.setString(2, user.getPassword());
            row = pstmt.executeUpdate();
        }catch(SQLException e) {
            e.printStackTrace();
        }finally {
            DBUtil.close(pstmt,conn);
        }
        return row;
    }

编写service层注册逻辑

UserService接口：

  public boolean register(User user);//注册

UserServiceImpl接口实现类

 @Override
    public boolean register(User user) {
        int row = userDao.insertUser(user);
        if(row>0){
            return true;
        }
        return false;
    }

编写RegisterServlet注册实现逻辑

RegisterServlet

package com.jishou.servlet;

import com.jishou.pojo.User;
import com.jishou.service.UserService;
import com.jishou.service.UserServiceImpl;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;

@WebServlet(name = "RegisterServlet",urlPatterns = "/register")
public class RegisterServlet extends HttpServlet {

    private UserService userService=new UserServiceImpl();

    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //取参
        req.setCharacterEncoding("utf-8");
        String username = req.getParameter("username");
        String password = req.getParameter("password");

        User qtUser=new User(username,password);

        //链接数据库添加
        boolean flag = userService.register(qtUser);

        /*resp.setCharacterEncoding("utf-8");
        resp.setContentType("text/html");
        PrintWriter out = resp.getWriter();

        //响应
        if(flag){
            out.println("<h1>注册成功<h1>");
        }else {
            out.println("<h1>注册失败<h1>");
        }
        out.flush();
        out.close();*/

        //注册成功 需要跳转到登录页面，注册失败 需要 回到注册页面，继续注册
        if(flag){
            //重定向 就表示重新定位到一个地址
            resp.sendRedirect("login.html");
        }else{
            resp.sendRedirect("register.html");
        }


    }
}

浏览器url访问测试,展示运行效果

http://localhost:8080/stuManage_04_war_exploded/register.html

eg4: 使用Servlet实现查询所有学生信息功能

创建数据库表

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编写实体类

Student

package com.jishou.pojo;

import java.util.Date;

public class Student {
    private Integer id;
    private String name;
    private Date birthday;
    private Integer age;
    private String address;
    private String photo;

    public Student() {
    }

    public Student(Integer id, String name, Date birthday, Integer age, String address, String photo) {
        this.id = id;
        this.name = name;
        this.birthday = birthday;
        this.age = age;
        this.address = address;
        this.photo = photo;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Date getBirthday() {
        return birthday;
    }

    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    public String getPhoto() {
        return photo;
    }

    public void setPhoto(String photo) {
        this.photo = photo;
    }

    @Override
    public String toString() {
        return "Student{" +
                "id=" + id +
                ", name='" + name + '\\'' +
                ", birthday=" + birthday +
                ", age=" + age +
                ", address='" + address + '\\'' +
                ", photo='" + photo + '\\'' +
                '}';
    }
}

数据访问层StudentDao,StudentDaoImpl查询所有

StudentDao

package com.jishou.dao;

import com.jishou.pojo.Student;

import java.util.List;

public interface StudentDao {

    public List<Student> queryAllStudents();
}

StudentDaoImpl

package com.jishou.dao;

import com.jishou.pojo.Student;
import com.jishou.util.DBUtil;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

public class StudentDaoImpl implements StudentDao{
    @Override
    public List<Student> queryAllStudents() {

        String sql="select * from stu";

        PreparedStatement pstmt=null;
        ResultSet rs=null;
        List<Student> list=new ArrayList<>();

        //2. 获取连接   修路
        Connection conn = DBUtil.getConnection();
        try {
            //3. 创建PreparedStatement   造车
            pstmt = conn.prepareStatement(sql);

            //4. 执行sql    拉货
            rs = pstmt.executeQuery();
            //5. 处理结果集 查询会有结果集  处理货物
            while (rs.next()) {
                int id = rs.getInt(1);
                String name = rs.getString(2);
                Date birthday = rs.getDate(3);
                int age = rs.getInt(4);
                String address = rs.getString(5);
                String photo = rs.getString(6);
                Student student=new Student(id,name,birthday,age,address,photo);
                list.add(student);
            }
        }catch (SQLException e){
            e.printStackTrace();
        }finally {
            //6. 关闭资源   货 车 路全都毁了
            DBUtil.close(rs,pstmt,conn);
        }

        return list;
    }
}

服务层service层接口和实现

StudentService

package com.jishou.service;

import com.jishou.pojo.Student;

import java.util.List;

public interface StudentService {
    public List<Student> queryAllStudents();
}

StudentServiceImpl

package com.jishou.service;

import com.jishou.dao.StudentDao;
import com.jishou.dao.StudentDaoImpl;
import com.jishou.pojo.Student;

import java.util.List;

public class StudentServiceImpl implements StudentService{

    private StudentDao studentDao=new StudentDaoImpl();

    @Override
    public List<Student> queryAllStudents() {
        return studentDao.queryAllStudents();
    }
}

查询所有的Servlet实现

ListServlet

package com.jishou.servlet;

import com.jishou.pojo.Student;
import com.jishou.service.StudentService;
import com.jishou.service.StudentServiceImpl;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.net.ServerSocket;
import java.util.List;

@WebServlet(name = "ListServlet",urlPatterns = "/list")
public class ListServlet extends HttpServlet {

    private StudentService studentService=new StudentServiceImpl();

    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //查询所有学生
        List<Student> list = studentService.queryAllStudents();
        //吧学生信息放在request对象里面
        req.setAttribute("list",list);
        //请求转发
        req.getRequestDispatcher("list.jsp").forward(req,resp);
    }
}

前端页面

list.jsp

<%@ page import="com.jishou.pojo.Student" %>
<%@ page import="java.util.List" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html>
<head>
    <title>Title</title>
</head>
<body>

<h1>学生管理系统</h1>
<table>
    <tr>
        <td>编号</td>
        <td>姓名</td>
        <td>出生日期</td>
        <td>年龄</td>
        <td>地址</td>
        <td><a href="">添加学生</a></td>
    </tr>


    <c:forEach var="s" items="${requestScope.list}">
        <tr>
            <td>${s.id}</td>
            <td>${s.name}</td>
            <td>${s.birthday}</td>
            <td>${s.age}</td>
            <td>${s.address}</td>
            <td>
                <a href="">修改</a>
                <a href="">删除</a>
            </td>
        </tr>
    </c:forEach>
</table>

</body>
</html>

浏览器url访问

http://localhost:8080/stuManage_04_war_exploded/list

eg5: 实现在首页展示当前用户名功能，退出系统功能，展示当前服务器总在线人数功能

LoginServlet：

package com.jishou.servlet;

import com.jishou.pojo.User;
import com.jishou.service.UserService;
import com.jishou.service.UserServiceImpl;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;
import java.io.PrintWriter;

@WebServlet(name = "LoginServlet",urlPatterns = "/login")
public class LoginServlet extends HttpServlet {

    private UserService userService=new UserServiceImpl();

    private Integer count=0;//总在线人数

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        //1. 取前台参数
        request.setCharacterEncoding("utf-8");
        String username = request.getParameter("username");
        String password = request.getParameter("password");

        User qtuser=new User(username,password);
        //2. 连接数据库查询
        User htuser = userService.login(qtuser);
        //3. 判断登录是否成功
       
        if(htuser!=null){
            //登录成功
			HttpSession session = request.getSession();
        	ServletContext servletContext = request.getServletContext();
            session.setAttribute("user",htuser);
            servletContext.setAttribute("count",++count);
            response.sendRedirect("list");
        }else{
            //登录失败
            response.sendRedirect("login.html");
        }
    }
}

LogOutServlet：

package com.jishou.servlet;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;

@WebServlet(name = "LogOutServlet",urlPatterns = "/logout")
public class LogOutServlet extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        HttpSession session = req.getSession();
        session.invalidate();//session失效
        //让总在线人数减少
        ServletContext servletContext = req.getServletContext();
        Integer count = (Integer) servletContext.getAttribute("count");
        servletContext.setAttribute("count",--count);
        resp.sendRedirect("login.html");
    }
}

list.jsp

加上下面代码：

<%
    List<Student> list = (List<Student>) request.getAttribute("list");
    User user = (User) request.getSession().getAttribute("user");
%>
<div id="login">欢迎<%=user.getUsername()%>登录 <a href="logout">退出系统</a></div>
<div id="count">当前共有<%=application.getAttribute("count")%>人在线</div>

eg6: 使用Servlet实现添加、删除和修改学生信息功能

思路：

添加：

<a href="add.jsp">添加学生</a>
当在主页面点击添加超链接时--->跳转到add.jsp----->add.jsp表单里面输入相应值时，跳转AddServlet,实现添加逻辑
----->AddServlet实现添加功能------>添加成功，跳转到ListServlet，添加失败，回到添加页面add.jsp
注意： 数据库表主键id自增，所以不用添加id属性

删除：

<a href="delete?id=<%=s.getId()%>">删除</a>
删除要根据id来删除该条数据信息；当点击删除超链接时，需要跳转到DeleteServlet，并吧要删除的id传过去,删除成功，再重新查询所有
超链接访问属于get请求方式，get请求走浏览器地址栏传参，所以href="delete?id=<%=s.getId()%>" 即可

修改：

修改的实现逻辑是在update.jsp里面在原来老数据的基础之上吧老数据修改成新数据，所以，修改的逻辑需要先根据id来查询单个，查询出来的对象信息回显到update.jsp表单里面，用户再在老数据的基础之上输入新数据，点击修改按钮，实现后台的修改功能；修改成功，回到主页面，查询所有；修改失败，回到update.jsp

list.jsp  <a href="load?id=<%=s.getId()%>">修改</a>  ----->LoadServlet 根据id查询单个---->
update.jsp 实现老数据回显------>用户在老数据的基础之上吧老数据修改成新数据，submit修改按钮----->
UpdateServlet 修改的后台实现----->修改成功，ListServlet；修改失败，回到update.jsp

注意： 由于数据库中birthday是date类型，他对应的java代码中的类型为java.sql.Date; 而平时java代码使用最多的是java.util.Date.

所以就涉及到不同的日期类型之间的转换，最好的方式就是写个日期工具类DateUtil:

DateUtil:

package com.jishou.util;


import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;

public class DateUtil {

    // util.date转换成sql.date
    public static java.sql.Date toSqlDate(Date date){

        return  new java.sql.Date(date.getTime());
    }

    // sql.date转换成util.date
    public static Date toUtilDate(java.sql.Date date){
        return new java.util.Date(date.getTime());
    }

    //String 转换成发 util.Date
    public static Date strToUtilDate(String dateStr){

        Date date = null;
        //注意format的格式要与日期String的格式相匹配
        DateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        try {
            date = sdf.parse(dateStr);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return date;
    }
    //util.Date转换为String

    public static String dateToStr(Date date){

        String dateStr = "";
        //format的格式可以任意
        DateFormat sdf = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");

        try {
            dateStr = sdf.format(date);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return dateStr;
    }



}

添加功能：

前台：add.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>

<center>
    <h1>添加学生</h1>

    <form action="add" method="post">
    <table width="50%" height="35%">
        <tr>
            <td>姓名</td>
            <td><input type="text" name="sname"></td>
        </tr>
        <tr>
            <td>年龄</td>
            <td><input type="text" name="age"></td>
        </tr>
        <tr>
            <td>生日</td>
            <td><input type="date" name="birthday"></td>
        </tr>
        <tr>
            <td>地址</td>
            <td><input type="text" name="address"></td>
        </tr>
        <tr>
            <td>头像</td>
            <td><input type="text" name="photo"></td>
        </tr>
        <tr>
            <td><input type="submit" value="添加"></td>
            <td><input type="reset" name="重置"></td>
        </tr>

    </table>
    </form>

</center>

</body>
</html>

后台：dao层：

StudentDao：

package com.jishou.dao;

import com.jishou.pojo.Student;

import java.util.List;

public interface StudentDao {

    public List<Student> queryAllStudents();

    public int addStudent(Student student);

    public int deleteStudentById(Integer id);

    public int updateStudent(Student student);

    public Student queryOneStudentById(Integer id);
}

StudentDaoImpl：

package com.jishou.dao;

import com.jishou.pojo.Student;
import com.jishou.util.DBUtil;
import com.jishou.util.DateUtil;

import java.sql.*;
import java.util.ArrayList;
import java.util.List;

public class StudentDaoImpl implements StudentDao{
    @Override
    public List<Student> queryAllStudents() {
        String sql="select * from stu";

        Connection conn = DBUtil.getConnection();
        List<Student> list = new ArrayList<>();
        PreparedStatement pstmt=null;
        ResultSet rs=null;
        try {
            pstmt= conn.prepareStatement(sql);
            rs= pstmt.executeQuery();

            while (rs.next()) {
                int id = rs.getInt(1);
                String sname = rs.getString(2);
                int age = rs.getInt(3);
                Date birthday = rs.getDate(4);
                String address = rs.getString(5);
                String photo = rs.getString(6);
                Student student = new Student(id, sname, age, birthday, address, photo);
                list.add(student);
            }
        }catch (SQLException e){
            e.printStackTrace();
        }finally {
            DBUtil.close(rs,pstmt,conn);
        }
        return list;
    }

    @Override
    public int addStudent(Student student) {
        String sql="INSERT INTO stu ( `sname`, `age`, `birthday`, `address`, `photo`) VALUES (?, ?, ?,?,?)";

        Connection conn = DBUtil.getConnection();
        PreparedStatement pstmt=null;
        int row=0;
        try {
            pstmt= conn.prepareStatement(sql);
            pstmt.setString(1,student.getSname());
            pstmt.setInt(2,student.getAge());
            pstmt.setDate(3, DateUtil.toSqlDate(student.getBirthday()));
            pstmt.setString(4,student.getAddress());
            pstmt.setString(5,student.getPhoto());
            row= pstmt.executeUpdate();

        }catch (SQLException e){
            e.printStackTrace();
        }finally {
            DBUtil.close(pstmt,conn);
        }
        return row;
    }

    @Override
    public int deleteStudentById(Integer id) {
        String sql="delete from stu where id=?";

        Connection conn = DBUtil.getConnection();

        PreparedStatement pstmt=null;
        int row=0;
        try {
            pstmt= conn.prepareStatement(sql);

            pstmt.setInt(1,id);

            row= pstmt.executeUpdate();

        }catch (SQLException e){
            e.printStackTrace();
        }finally {
            DBUtil.close(pstmt,conn);
        }
        return row;
    }

    @Override
    public int updateStudent(Student student) {
        String sql="UPDATE stu SET  `sname`=?, `age`=?, `birthday`=?, `address`=?, `photo`=? WHERE `id`=?";

        Connection conn = DBUtil.getConnection();
        PreparedStatement pstmt=null;
        int row=0;
        try {
            pstmt= conn.prepareStatement(sql);
            pstmt.setString(1,student.getSname());
            pstmt.setInt(2,student.getAge());
            pstmt.setDate(3, DateUtil.toSqlDate(student.getBirthday()));
            pstmt.setString(4,student.getAddress());
            pstmt.setString(5,student.getPhoto());
            pstmt.setInt(6,student.getId());
            row= pstmt.executeUpdate();

        }catch (SQLException e){
            e.printStackTrace();
        }finally {
            DBUtil.close(pstmt,conn);
        }
        return row;
    }

    @Override
    public Student queryOneStudentById(Integer id) {
        String sql="select * from stu where id=?";

        Connection conn = DBUtil.getConnection();
        PreparedStatement pstmt=null;
        ResultSet rs=null;
        Student student=null;
        try {
            pstmt= conn.prepareStatement(sql);
            pstmt.setInt(1,id);
            rs= pstmt.executeQuery();

            if (rs.next()) {
                int idd = rs.getInt(1);
                String sname = rs.getString(2);
                int age = rs.getInt(3);
                Date birthday = rs.getDate(4);
                String address = rs.getString(5);
                String photo = rs.getString(6);
                student = new Student(idd, sname, age, birthday, address, photo);

            }
        }catch (SQLException e){
            e.printStackTrace();
        }finally {
            DBUtil.close(rs,pstmt,conn);
        }
        return student;
    }
}

service层：

StudentService：

package com.jishou.service;

import com.jishou.pojo.Student;

import java.util.List;

public interface StudentService {

    public List<Student> queryAllStudents();

    public boolean addStudent(Student student);

    public boolean deleteStudentById(Integer id);

    public boolean updateStudent(Student student);

    public Student queryOneStudentById(Integer id);
}

StudentServiceImpl：

package com.jishou.service;

import com.jishou.dao.StudentDao;
import com.jishou.dao.StudentDaoImpl;
import com.jishou.pojo.Student;

import java.util.List;

public class StudentServiceImpl implements StudentService{

    private StudentDao studentDao=new StudentDaoImpl();

    @Override
    public List<Student> queryAllStudents() {
        return studentDao.queryAllStudents();
    }

    @Override
    public boolean addStudent(Student student) {
        int row = studentDao.addStudent(student);
        if(row>0){
            return true;
        }
        return false;
    }

    @Override
    public boolean deleteStudentById(Integer id) {
        int row = studentDao.deleteStudentById(id);
        if(row>0){
            return true;
        }

        return false;
    }

    @Override
    public boolean updateStudent(Student student) {
        int row = studentDao.updateStudent(student);
        if(row>0){
            return true;
        }
        return false;
    }

    @Override
    public Student queryOneStudentById(Integer id) {
        return studentDao.queryOneStudentById(id);
    }
}

servlet：

AddServlet：

package com.jishou.servlet;

import com.jishou.pojo.Student;
import com.jishou.service.StudentService;
import com.jishou.service.StudentServiceImpl;
import com.jishou.util.DateUtil;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.Date;

@WebServlet(name = "AddServlet",urlPatterns = "/add")
public class AddServlet extends HttpServlet {

    private StudentService studentService=new StudentServiceImpl();

    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        //取参数值
        req.setCharacterEncoding("utf-8");
        String sname = req.getParameter("sname");
        //将String的年龄转换为int类型
        Integer age = Integer.parseInt(req.getParameter("age"));
        String date = req.getParameter("birthday");
        //将String日期类型转换为java.util.Date
        Date birthday = DateUtil.strToUtilDate(date);
        String address = req.getParameter("address");
        String photo = req.getParameter("photo");

        Student student=new Student(sname,age,birthday,address,photo);
        //实现修改逻辑
        boolean flag = studentService.addStudent(student);
        if(flag){
            //添加成功
            resp.sendRedirect("list");
        }else{
            //添加失败
            resp.sendRedirect("add.jsp");
        }

    }
}

删除功能：

前台：list.jsp:

 <a href="delete?id=<%=s.getId()%>">删除</a>

后台：DeleteServlet：

package com.jishou.servlet;

import com.jishou.service.StudentService;
import com.jishou.service.StudentServiceImpl;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@WebServlet(name = "DeleteServlet",urlPatterns = "/delete")
public class DeleteServlet extends HttpServlet {
    private StudentService studentService=new StudentServiceImpl();
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        //取参
        String ids = req.getParameter("id");
        //类型转换
        Integer id=Integer.parseInt(ids);

        boolean flag = studentService.deleteStudentById(id);

        if(flag){
            resp.sendRedirect("list");
        }

    }
}

修改功能：

list.jsp:

 <a href="load?id=<%=s.getId()%>">修改</a>

LoadServlet:

package com.jishou.servlet;

import com.jishou.pojo.Student;
import com.jishou.service.StudentService;
import com.jishou.service.StudentServiceImpl;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@WebServlet(name = "LoadServlet",urlPatterns = "/load")
public class LoadServlet extends HttpServlet {

    private StudentService studentService=new StudentServiceImpl();

    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        Integer id=Integer.parseInt(req.getParameter("id"));
        //根据id查询单个
        Student student = studentService.queryOneStudentById(id);
        req.setAttribute("s",student);
        //请求转发
        req.getRequestDispatcher("update.jsp").forward(req,resp);

    }
}

update.jsp:

<%@ page contentType="text/html;charset=UTF-8" language="java" isELIgnored="false" %>
<html>
<head>
    <title>Title</title>
</head>
<body>

<center>
    <h1>修改学生</h1>

    <form action="update" method="post">
    <table width="50%" height="35%">
        <tr>
            <td>编号</td>
            <td><input type="text" name="id" value="${s.id}" readonly></td>
        </tr>
        <tr>
            <td>姓名</td>
            <td><input type="text" name="sname" value="${s.sname}"></td>
        </tr>
        <tr>
            <td>年龄</td>
            <td><input type="text" name="age" value="${s.age}"></td>
        </tr>
        <tr>
            <td>生日</td>
            <td><input type="date" name="birthday" value="${s.birthday}"></td>
        </tr>
        <tr>
            <td>地址</td>
            <td><input type="text" name="address" value="${s.address}"></td>
        </tr>
        <tr>
            <td>头像</td>
            <td><input type="text" name="photo" value="${s.photo}"></td>
        </tr>
        <tr>
            <td><input type="submit" value="修改"></td>
            <td><input type="reset" name="重置"></td>
        </tr>

    </table>
    </form>

</center>

</body>
</html>

UpdateServlet:

package com.jishou.servlet;

import com.jishou.pojo.Student;
import com.jishou.service.StudentService;
import com.jishou.service.StudentServiceImpl;
import com.jishou.util.DateUtil;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.Date;

@WebServlet(name = "UpdateServlet",urlPatterns = "/update")
public class UpdateServlet extends HttpServlet {

    private StudentService studentService=new StudentServiceImpl();

    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        //取参数值
        req.setCharacterEncoding("utf-8");
        Integer id = Integer.parseInt(req.getParameter("id"));
        String sname = req.getParameter("sname");
        //将String的年龄转换为int类型
        Integer age = Integer.parseInt(req.getParameter("age"));
        String date = req.getParameter("birthday");
        //将String日期类型转换为java.util.Date
        Date birthday = DateUtil.strToUtilDate(date);
        String address = req.getParameter("address");
        String photo = req.getParameter("photo");

        Student student=new Student(id,sname,age,birthday,address,photo);

        //实现修改逻辑
        boolean flag = studentService.updateStudent(student);
        if(flag){
            //修改成功
            resp.sendRedirect("list");
        }else{
            //修改失败
            resp.sendRedirect("update.jsp");
        }

    }
}

eg7：使用Servlet实现学生信息的分页展示

编写PageBean : PageBean对象就是当前页面对象，包含了当前页面所包含的所有信息

package com.jishou.pojo;

import java.util.List;
/**
 * 存放分页相关的数据
 *
 */
public class PageBean<T> {
    //基本属性
    private int currentPageNum;//当前页数，由用户指定
    private int pageSize = 5;//每页显示的条数，固定的
    private int totalRecords;//总记录条数，数据库查出来的
    private int totalPageNum;//总页数，计算出来的
    private List<T> list;//已经分好页的结果集


    public int getCurrentPageNum() {
        return currentPageNum;
    }

    public void setCurrentPageNum(int currentPageNum) {
        this.currentPageNum = currentPageNum;
    }

    public int getPageSize() {
        return pageSize;
    }

    public void setPageSize(int pageSize) {
        this.pageSize = pageSize;
    }

    public int getTotalRecords() {
        return totalRecords;
    }

    public void setTotalRecords(int totalRecords) {
        this.totalRecords = totalRecords;
        //总记录数固定，页面大小固定，计算出总页数
        if(this.totalRecords%this.pageSize==0){
            this.totalPageNum=this.totalRecords/this.pageSize;
        }else{
            this.totalPageNum=this.totalRecords/this.pageSize+1;
        }
    }

    public int getTotalPageNum() {
        return totalPageNum;
    }

    public void setTotalPageNum(int totalPageNum) {
        this.totalPageNum = totalPageNum;
    }

    public List getList() {
        return list;
    }

    public void setList(List list) {
        this.list = list;
    }

    @Override
    public String toString() {
        return "PageBean{" +
                "currentPageNum=" + currentPageNum +
                ", pageSize=" + pageSize +
                ", totalRecords=" + totalRecords +
                ", totalPageNum=" + totalPageNum +
                ", list=" + list +
                '}';
    }
}

dao层编写获取总记录数和分页查询的逻辑

StudentDao:

//查询总记录数
public int getTotalRecords();

//分页查询学生信息 参数为当前页和页面大小
public List<Student> queryStudentsByPage(int currentPage,int pageSize);

StudentDaoImpl:

@Override
public int getTotalRecords() {
    String sql="select count(*) from stu";

    Connection conn = DBUtil.getConnection();
    PreparedStatement pstmt=null;
    ResultSet rs=null;
    int count=0;
    try {
        pstmt= conn.prepareStatement(sql);
        rs= pstmt.executeQuery();

        if (rs.next()) {
            count = rs.getInt(1);
        }
    }catch (SQLException e){
        e.printStackTrace();
    }finally {
        DBUtil.close(rs,pstmt,conn);
    }
    return count;
}

@Override
public List<Student> queryStudentsByPage(int currentPage, int pageSize) {
    String sql="select * from stu limit ?,?";

    Connection conn = DBUtil.getConnection();
    List<Student> list = new ArrayList<>();
    PreparedStatement pstmt=null;
    ResultSet rs=null;
    try {
        pstmt= conn.prepareStatement(sql);
        //注意第一个参数值的写法
        pstmt.setInt(1,(currentPage-1)*pageSize);
        pstmt.setInt(2,pageSize);
        rs= pstmt.executeQuery();

        while (rs.next()) {
            int id = rs.getInt(1);
            String sname = rs.getString(2);
            int age = rs.getInt(3);
            Date birthday = rs.getDate(4);
            String address = rs.getString(5);
            String photo = rs.getString(6);
            Student student = new Student(id, sname, age, birthday, address, photo);
            list.add(student);
        }
    }catch (SQLException e){
        e.printStackTrace();
    }finally {
        DBUtil.close(rs,pstmt,conn);
    }
    return list;
}

service层代码

StudentService:

//分页查询学生信息 参数为当前页和页面大小
public PageBean<Student> queryStudentsByPage(int currentPage, int pageSize);

StudentServiceImpl:

@Override
public PageBean<Student> queryStudentsByPage(int currentPage, int pageSize) {
    List<Student> students = studentDao.queryStudentsByPage(currentPage, pageSize);
    int total = studentDao.getTotalRecords();
    PageBean<Student> pageBean=new PageBean<>();
    pageBean.setPageSize(pageSize);//设置页面大小
    pageBean.setTotalRecords(total);//设置总记录数
    pageBean.setCurrentPageNum(currentPage);//设置当前页
    pageBean.setList(students);//设置当前页数据
    return pageBean;
}

ListPageServlet 分页的Servlet

ListPageServlet:

package com.jishou.servlet;

import com.jishou.pojo.PageBean;
import com.jishou.pojo.Student;
import com.jishou.service.StudentService;
import com.jishou.service.StudentServiceImpl;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.List;

@WebServlet(name = "ListPageServlet",urlPatterns = "/listpage")
public class ListPageServlet extends HttpServlet {

    private StudentService studentService=new StudentServiceImpl();

    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        //取当前页
        String currentPage= req.getParameter("currentPage");
        //第一次访问，默认currentPage 访问第一页
        if(currentPage==null) {
            currentPage = "1";
        }
        Integer currentPageNum=Integer.parseInt(currentPage);
        //页面大小暂设置成固定值3

        //分页查询所有
        PageBean<Student> pageBean = studentService.queryStudentsByPage(currentPageNum,3);
        //servlet重在业务逻辑，取值传值 jsp侧重于页面显示
        req.setAttribute("page",pageBean);
        //请求转发
        req.getRequestDispatcher("listpage.jsp").forward(req,resp);
    }
}

注意：

登录成功之后跳转到llistpage

response.sendRedirect("listpage");

前端 listpage.jsp

<%@ page import="com.jishou.pojo.Student" %>
<%@ page import="java.util.List" %>
<%@ page import="com.jishou.pojo.User" %>
<%@ page import="com.jishou.pojo.PageBean" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" isELIgnored="false" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html>
<head>
    <title>Title</title>
    <style>
        #login{
            float: left;
        }
        #count{
            float: right;
        }
    </style>
</head>
<body>
<div id="login">欢迎${sessionScope.user.username}登录 <a href="logout">退出系统</a></div>
<div id="count">当前共有${applicationScope.count}人在线</div>
<center>
<h1>学生管理系统</h1>
<table width="70%" height="50%">
    <tr>
        <td>头像</td>
        <td>Id</td>
        <td>姓名</td>
        <td>年龄</td>
        <td>生日</td>
        <td>地址</td>
        <td>
            <a href="add.jsp">添加学生</a>
        </td>
    </tr>
    <c:if test="${requestScope.page!=null}">
        <c:if test="${requestScope.page.list ne null and requestScope.page.list.size() gt 0}">

            <c:forEach var="s" items="${requestScope.page.list}">
                <tr>
                    <td>
                        <img src="${s.photo}" width="20px" height="20px"/>
                    </td>
                    <td>${s.id}</td>
                    <td>${s.sname}</td>
                    <td>${s.age}</td>
                    <td>${s.birthday}</td>
                    <td>${s.address}</td>

                    <td>
                        <a href="load?id&#以上是关于使用Servlet+JSP实现学生管理系统的主要内容，如果未能解决你的问题，请参考以下文章 
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使用Servlet+JSP实现学生管理系统

文章目录

使用Servlet+JSP实现学生管理系统

eg1: 使用servlet来实现登录功能

eg2: 使用servlet来实现登录功能

1.创建数据库表 mysql

2.创建web project

3. 在web目录下创建登录页面 login.html

4.编写实体类User

5.编写数据访问层 UserDao接口 和 接口实现类

6.编写service层接口和实现类

7.编写Servlet的登录实现逻辑

8.浏览器url访问登录页面，展示运行效果

eg3: 使用Servlet实现注册功能

eg4: 使用Servlet实现查询所有学生信息功能

eg5: 实现在首页展示当前用户名功能，退出系统功能，展示当前服务器总在线人数功能

eg6: 使用Servlet实现添加、删除和修改学生信息功能

eg7： 使用Servlet实现学生信息的分页展示

5.编写数据访问层 UserDao接口和接口实现类

eg7：使用Servlet实现学生信息的分页展示