前言

项目发布于半年前（2023年9月），这次是复习~来考古 =_=
点击前往 GitHub 项目页
通过该项目，可以加深对 JavaBean 使用以及对 JavaWeb 开发的理解
技术：

  • JavaWeb（Servlet + JSP）
  • MySQL
  • JDBC

1. 关于 JavaBean

JavaBean 其实就是 Java 中的实体类，负责数据的封装。我们可以创建 bean 包存储 JavaBean

  • 可以理解为符合某种规范的 Java 类
    比如：
    • 无参数构造方法
    • 属性私有化
    • 对外公开提供 get 和 set 方法
    • 实现 java.io.Serializable 接口
    • 重写 toString
    • 重写 hashCode + equals
    • …

2. 学生管理系统分析

职责分析

  • 数据库
    一个数据库，两张表
    • 学生信息（学号、姓名、性别、联系方式）
    • 管理员信息（id、username、password）
  • 前端，提供一套页面
    • 登录页面
    • 管理页面：列表页、详情页、修改页、新增页
  • 后端
    连接数据库，查询学生信息，实现与前端相关的一系列功能

功能分析

  • 管理员登录功能
    成功则跳转到学生列表页面，失败则跳转到失败页面
    可以从失败页面返回登录页面
  • 查看学生列表，列表中有以下功能
    • 查看学生详情
    • 修改学生信息
    • 删除学生信息
    • 新增学生信息
    • 退出系统

3. 项目实现

目录结构

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src
  |--- com.xxx.student_manage
      |--- bean
            |--- Student
      |--- filter
            |--- LoginCheckFilter
      |--- utils
            |--- DBUtil
      |--- web.action
            |--- StudentServlet
            |--- UserServlet
            |--- WelcomeServlet
|--- resources
      |--- jdbc.properties

web
  |--- WEB-INF
      |--- lib
            |--- jakarta.servlet.jsp.jstl-2.0.0.jar
            |--- jakarta.servlet.jsp.jstl-api-2.0.0.jar
            |--- mysql-connector-j-8.0.33.jar
      |--- web.xml
  |--- add.jsp
  |--- detail.jsp
  |--- edit.jsp
  |--- index.jsp
  |--- list.jsp
  |--- login_error.jsp

3.1 数据库：MySQL

准备一个数据库，数据库中创建学生表和管理员用户表

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# 学生表
set character_set_client = 'utf8';
drop table if exists t_student;
create table t_student(
    sno       int primary key,
    sname     varchar(255) not null,
    ssex      varchar(255) not null,
    telephone varchar(255) not null
);
insert into t_student(sno, sname, ssex, telephone)
values (001, 'tom', '男', '1111111');
insert into t_student(sno, sname, ssex, telephone)
values (002, 'jack', '男', '1112222');
insert into t_student(sno, sname, ssex, telephone)
values (003, '张三', '男', '1113333');
commit;
select *
from t_student;
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# 管理员用户表
set character_set_client = 'utf8';
drop table if exists t_user;
create table t_user(
    id int primary key,
    username varchar(255) not null,
    password varchar(255) not null
);
insert into t_user (id, username, password)
values (01, 'admin', '123');
insert into t_user(id, username, password)
values (02, 'tom', '123321');
commit;
select * from t_user;

3.2 前端：JSP

登录页

index.jsp

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<%@ page contentType="text/html;charset=UTF-8" %>
<html>
  <head>
    <title>欢迎使用学生管理系统</title>
    <base href="${pageContext.request.scheme}://${pageContext.request.serverName}:${pageContext.request.serverPort}${pageContext.request.contextPath}/">
  </head>
  <body>
    <h1>您好，请登录</h1>
    <hr>
    <form action="user/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">
      <input type="checkbox" name="f" value="1"/>十天内免登录<br>
    </form>
  </body>
</html>

登录失败页

login_error.jsp

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<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>error</title>
</head>
<body>
    <h1>登录失败，<a href="${pageContext.request.contextPath}">请重新登录</a></h1>
</body>
</html>

学生列表页

list.jsp

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<%@ page contentType="text/html;charset=UTF-8" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>

<html>
<head>
    <title>学生列表页面</title>
    <base href="${pageContext.request.scheme}://${pageContext.request.serverName}:${pageContext.request.serverPort}${pageContext.request.contextPath}/">
</head>
<body>
<script>
    function del(sno) {
        if (window.confirm("确定删除该同学的信息吗？？？")) {
            document.location.href = "${pageContext.request.contextPath}/student/delete?sno=" + sno;
        }
    }
</script>
<h1>学生列表</h1>
<hr>
<table>
    <tr>
        <td>序号</td>
        <td>学号</td>
        <td>姓名</td>
        <td>操作</td>
    </tr>
    <c:forEach items="${stuList}" varStatus="stuStatus" var="student">
        <tr>
            <td>${stuStatus.count}</td>
            <td>${student.sno}</td>
            <td>${student.sname}</td>
            <td>
                <a href="student/detail?f=detail&sno=${student.sno}">详情</a>
                <a href="student/detail?f=edit&sno=${student.sno}">修改</a>
                <a href="javascript:void(0)" onclick="del(${student.sno})">删除</a>
            </td>
        </tr>
    </c:forEach>
</table>
<a href="add.jsp">新增学生</a>
<br>
<a href="user/exit">退出系统</a>
</body>
</html>

学生详情页

detail.jsp

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<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
  <head>
    <title>学生详细信息</title>
  </head>
  <body>
    <h1>学生详细信息</h1>
    <hr>
    学号：${student.sno}<br>
    姓名：${student.sname}<br>
    性别：${student.ssex}<br>
    联系电话：${student.telephone}<br>
    <input type="button" value="后退" onclick="window.history.back()">
  </body>
</html>

学生修改页

edit.jsp

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<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>修改学生信息</title>
    <base href="${pageContext.request.scheme}://${pageContext.request.serverName}:${pageContext.request.serverPort}${pageContext.request.contextPath}/">
</head>
<body>
    <h1>修改学生信息</h1>
    <hr>
    <form action="student/modify" method="post">
        学号：<input type="text" name="sno" value="${student.sno}" readonly><br>
        姓名：<input type="text" name="sname" value="${student.sname}"><br>
        性别：${student.ssex}<br>
        联系电话：<input type="text" name="telephone" value="${student.telephone}"><br>
        <input type="submit" value="保存">
    </form>
</body>
</html>

新增学生页

add.jsp

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<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>新增学生</title>
    <base href="${pageContext.request.scheme}://${pageContext.request.serverName}:${pageContext.request.serverPort}${pageContext.request.contextPath}/">
</head>
<body>
    <h1>新增学生</h1>
    <hr>
    <form action="student/add" method="post">
        学号：<input type="text" name="sno"><br>
        姓名：<input type="text" name="sname"><br>
        性别：男<input type="radio" name="ssex" value="男"> 女<input type="radio" name="ssex" value="女"><br>
        联系电话：<input type="text" name="telephone"><br>
        <input type="submit" value="保存">
    </form>
</body>
</html>

3.3 后端

JavaBean

bean 包下新建 Student 类，用来封装学生信息

代码如下：

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/**
 * @author ShameYang
 * @date 2023/9/10 16:45
 * @description 学生类
 */
public class Student {
    private String sno;
    private String sname;
    private String ssex;
    private String telephone;

    public String getSno() {
        return sno;
    }

    public void setSno(String sno) {
        this.sno = sno;
    }

    public String getSname() {
        return sname;
    }

    public void setSname(String sname) {
        this.sname = sname;
    }

    public String getSsex() {
        return ssex;
    }

    public void setSsex(String ssex) {
        this.ssex = ssex;
    }

    public String getTelephone() {
        return telephone;
    }

    public void setTelephone(String telephone) {
        this.telephone = telephone;
    }

    public Student() {
    }

    public Student(String sno, String sname, String ssex, String telephone) {
        this.sno = sno;
        this.sname = sname;
        this.ssex = ssex;
        this.telephone = telephone;
    }


    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Student student = (Student) o;
        return Objects.equals(sno, student.sno) && Objects.equals(sname, student.sname) && Objects.equals(ssex, student.ssex) && Objects.equals(telephone, student.telephone);
    }

    @Override
    public int hashCode() {
        return Objects.hash(sno, sname, ssex, telephone);
    }
}

封装 DBUtil

Java 访问数据库，JDBC 是必不可少的。我们在 utils 包下封装一个 DBUtil，专门用来完成 JDBC 操作

具体代码如下：

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/**
 * @author ShameYang
 * @date 2023/9/10 15:37
 * @description JDBC 工具类
 */
public class DBUtil {
    private static ResourceBundle bundle = ResourceBundle.getBundle("resources.jdbc");
    private static String driver = bundle.getString("driver");
    private static String url = bundle.getString("url");
    private static String user = bundle.getString("user");
    private static String password = bundle.getString("password");

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

    /**
     * 获取数据库连接对象
     * @return conn 连接对象
     * @throws SQLException
     */
    public static Connection getConnection() throws SQLException {
        Connection conn = DriverManager.getConnection(url, user, password);
        return conn;
    }

    /**
     * 释放资源
     * @param conn 连接对象
     * @param ps 数据库操作对象
     * @param rs 结果集对象
     */
    public static void close(Connection conn, Statement ps, ResultSet rs) {
        if (conn != null) {
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (ps != null) {
            try {
                ps.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (rs != null) {
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}

我们可以发现 ResourceBundle.getBundle("resources.jdbc"); 使用了 ResourceBundle 类，用来加载 JDBC 的配置文件
所以，我们还需要在 resources 包下，新建一个 jdbc.properties 配置文件用来存放连接数据库的一些配置

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driver=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://localhost:3306/数据库名
user=你的用户
password=你的密码

Servlet 类

管理学生信息
StudentServlet：

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/**
 * @author ShameYang
 * @date 2023/9/10 16:36
 * @description 学生列表
 */
@WebServlet({"/student/list", "/student/detail", "/student/delete",
        "/student/add", "/student/modify"})
public class StudentServlet extends HttpServlet {
    @Override
    protected void service(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
            String servletPath = request.getServletPath();
            switch (servletPath) {
                case "/student/list" -> doList(request, response);
                case "/student/detail" -> doDetail(request, response);
                case "/student/delete" -> doDel(request, response);
                case "/student/add" -> doAdd(request, response);
                case "/student/modify" -> doModify(request, response);
            }
    }

    /**
     * 连接数据库，查询所有学生信息，将信息收集好后跳转到 JSP 页面展示
     * @param request 请求
     * @param response 响应
     * @throws ServletException 异常
     * @throws IOException 异常
     */
    private void doList(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        List<Student> stus = new ArrayList<>();

        Connection conn = null;
        PreparedStatement ps = null;
        ResultSet rs = null;
        try {
            conn = DBUtil.getConnection();
            String sql = "select sno, sname, ssex, telephone from t_student";
            ps = conn.prepareStatement(sql);
            rs = ps.executeQuery();
            while (rs.next()) {
                String sno = rs.getString("sno");
                String sname = rs.getString("sname");
                String ssex = rs.getString("ssex");
                String telephone = rs.getString("telephone");
                // 将以上数据封装为 java 对象
                Student student = new Student();
                student.setSno(sno);
                student.setSname(sname);
                student.setSsex(ssex);
                student.setTelephone(telephone);
                // 将学生对象放到 list 集合中
                stus.add(student);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            DBUtil.close(conn, ps, rs);
        }
        // 将集合放到请求域中
        request.setAttribute("stuList", stus);
        // 转发到 JSP 页面
        request.getRequestDispatcher("/list.jsp").forward(request, response);
    }

    /**
     * 详情功能
     * @param request 请求
     * @param response 响应
     * @throws ServletException 异常
     * @throws IOException 异常
     */
    private void doDetail(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String sno = request.getParameter("sno");
        Student student = new Student();
        student.setSno(sno);
        Connection conn = null;
        PreparedStatement ps = null;
        ResultSet rs = null;
        try {
            conn = DBUtil.getConnection();
            String sql = "select sno, sname, ssex, telephone from t_student where sno=?";
            ps = conn.prepareStatement(sql);
            ps.setString(1, sno);
            rs = ps.executeQuery();
            if (rs.next()) {
                String sname = rs.getString("sname");
                String ssex = rs.getString("ssex");
                String telephone = rs.getString("telephone");

                student.setSname(sname);
                student.setSsex(ssex);
                student.setTelephone(telephone);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            DBUtil.close(conn, ps, rs);
        }

        request.setAttribute("student", student);

        // 这样写可以转发给修改功能使用
        request.getRequestDispatcher("/" + request.getParameter("f") + ".jsp").forward(request, response);
    }

    /**
     * 删除功能
     * @param request 请求
     * @param response 响应
     * @throws ServletException 异常
     * @throws IOException 异常
     */
    private void doDel(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String sno = request.getParameter("sno");
        Connection conn = null;
        PreparedStatement ps = null;
        // 记录是否执行
        int count = 0;
        try {
            conn = DBUtil.getConnection();
            String sql = "delete from t_student where sno=?";
            ps = conn.prepareStatement(sql);
            ps.setString(1, sno);
            count = ps.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            DBUtil.close(conn, ps, null);
        }

        // 删除成功，重定向至学生列表页面
        if (count == 1) {
            response.sendRedirect(request.getContextPath() + "/student/list");
        }
    }

    /**
     * 新增学生
     * @param request 请求
     * @param response 响应
     * @throws ServletException 异常
     * @throws IOException 异常
     */
    private void doAdd(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String sno = request.getParameter("sno");
        String sname = request.getParameter("sname");
        String ssex = request.getParameter("ssex");
        String telephone = request.getParameter("telephone");
        Connection conn = null;
        PreparedStatement ps = null;
        int count = 0;

        try {
            conn = DBUtil.getConnection();
            String sql = "insert into t_student(sno, sname, ssex, telephone) " +
                    "VALUES (?, ?, ?, ?)";
            ps = conn.prepareStatement(sql);
            ps.setString(1, sno);
            ps.setString(2, sname);
            ps.setString(3, ssex);
            ps.setString(4, telephone);
            count = ps.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            DBUtil.close(conn, ps, null);
        }

        if (count == 1) {
            response.sendRedirect(request.getContextPath() + "/student/list");
        }
    }

    /**
     * 修改学生信息
     * @param request 请求
     * @param response 响应
     * @throws ServletException 异常
     * @throws IOException 异常
     */
    private void doModify(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String sno = request.getParameter("sno");
        String sname = request.getParameter("sname");
        String telephone = request.getParameter("telephone");

        Connection conn = null;
        PreparedStatement ps = null;
        int count = 0;
        try {
            conn = DBUtil.getConnection();
            String sql = "update t_student set sname=?, telephone=? where sno=?";
            ps = conn.prepareStatement(sql);
            ps.setString(1, sname);
            ps.setString(2, telephone);
            ps.setString(3, sno);
            count = ps.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            DBUtil.close(conn, ps, null);
        }

        if (count == 1) {
            response.sendRedirect(request.getContextPath() + "/student/list");
        }
    }
}

管理员登录（Session&Cookie）
UserServlet：

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/**
 * @author ShameYang
 * @date 2023/9/11 08:17
 * @description 用户登录
 */
@WebServlet({"/user/login", "/user/exit"})
public class UserServlet extends HttpServlet {
    @Override
    protected void service(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String servletPath = request.getServletPath();
        switch (servletPath) {
            case "/user/login" -> doLogin(request, response);
            case "/user/exit" -> doExit(request, response);
        }
    }

    private void doExit(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        HttpSession session = request.getSession(false);
        if (session != null) {
            // 手动销毁 session
            session.invalidate();
            // 清除 cookie
            Cookie[] cookies = request.getCookies();
            if (cookies != null) {
                for (Cookie cookie : cookies) {
                    cookie.setMaxAge(0);
                    // 这里的关联路径要与之前的一致
                    cookie.setPath(request.getContextPath());
                    response.addCookie(cookie);
                }
            }
            response.sendRedirect(request.getContextPath());
        }
    }

    private void doLogin(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String username = request.getParameter("username");
        String password = request.getParameter("password");

        Connection conn = null;
        PreparedStatement ps = null;
        ResultSet rs = null;
        Boolean success = false;
        try {
            conn = DBUtil.getConnection();
            String sql = "select id, username, password from t_user where username=? and password=?";
            ps = conn.prepareStatement(sql);
            ps.setString(1, username);
            ps.setString(2, password);
            rs = ps.executeQuery();
            if (rs.next()) {
                success = true;
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            DBUtil.close(conn, ps, rs);
        }

        // 登陆成功，重定向至学生列表
        if (success) {
            // session
            HttpSession session = request.getSession();
            session.setAttribute("username", username);
            // cookie
            String f = request.getParameter("f");
            if ("1".equals(f)) {
                Cookie cookie1 = new Cookie("username", username);
                Cookie cookie2 = new Cookie("password", password);
                // 设置关联路径
                cookie1.setPath(request.getContextPath());
                cookie2.setPath(request.getContextPath());
                // 设置有效期十天
                cookie1.setMaxAge(60 * 60 * 24 * 10);
                cookie2.setMaxAge(60 * 60 * 24 * 10);
                // 发送到服务器
                response.addCookie(cookie1);
                response.addCookie(cookie2);
            }
            response.sendRedirect(request.getContextPath() + "/student/list");
        } else {
            response.sendRedirect(request.getContextPath() + "/login_error.jsp");
        }
    }
}

登录过滤
WelcomeServlet：

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/**
 * @author ShameYang
 * @date 2023/9/11 09:31
 * @description 欢迎页实现 cookie
 */
@WebServlet("/welcome")
public class WelcomeServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        // 获取 cookie
        Cookie[] cookies = request.getCookies();
        String username = null;
        String password = null;
        if (cookies != null) {
            for (Cookie cookie : cookies) {
                String name = cookie.getName();
                if ("username".equals(name)) {
                    username = cookie.getValue();
                } else if ("password".equals(name)) {
                    password = cookie.getValue();
                }
            }
        }

        if (username != null && password != null) {
            // 连接数据库，验证用户名密码
            Connection conn = null;
            PreparedStatement ps = null;
            ResultSet rs = null;
            Boolean success = false;
            try {
                conn = DBUtil.getConnection();
                String sql = "select * from t_user where username=? and password=?";
                ps = conn.prepareStatement(sql);
                ps.setString(1, username);
                ps.setString(2, password);
                rs = ps.executeQuery();
                if (rs.next()) {
                    success = true;
                }
            } catch (SQLException e) {
                e.printStackTrace();
            } finally {
                DBUtil.close(conn, ps, rs);
            }

            if (success) {
                HttpSession session = request.getSession();
                session.setAttribute("username", username);

                response.sendRedirect(request.getContextPath() + "/student/list");
            } else {
                response.sendRedirect(request.getContextPath() + "/index.jsp");
            }
        } else {
            response.sendRedirect(request.getContextPath() + "/index.jsp");
        }
    }
}

filter 包下 LoginCheckFilter：

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/**
 * @author ShameYang
 * @date 2023/9/13 15:13
 * @description 登录检查过滤器
 */
public class LoginCheckFilter implements Filter {
    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain)
            throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) servletRequest;
        HttpServletResponse response = (HttpServletResponse) servletResponse;

        HttpSession session = request.getSession(false);
        if (session != null && session.getAttribute("username") != null) {
            filterChain.doFilter(request, response);
        } else {
            response.sendRedirect(request.getContextPath() + "/index.jsp");
        }
    }
}

web.xml

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<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">
    <welcome-file-list>
        <welcome-file>welcome</welcome-file>
    </welcome-file-list>

    <filter>
        <filter-name>loginFilter</filter-name>
        <filter-class>com.shameyang.student_manage.filter.LoginCheckFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>loginFilter</filter-name>
        <url-pattern>/student/*</url-pattern>
    </filter-mapping>
</web-app>

4. 总结

  • JSP：我们使用 base 标签 + EL 表达式，这样简化了地址的编写和属性的访问
    示例：

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    <base href="${pageContext.request.scheme}://${pageContext.request.serverName}:${pageContext.request.serverPort}${pageContext.request.contextPath}/">

    登录失败，<a href="${pageContext.request.contextPath}">请重新登录</a>

    <form action="student/add" method="post">...</form>

  • Servlet：根据请求路径，执行相应的方法
    访问数据时，我们要将数据封装到集合或对象中，然后把集合或对象放到请求域中，转发到相应页面

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    request.setAttribute("name", 集合或对象);

    request.getRequestDispatcher("/xxx").forward(request, response);

    使用或修改数据时，使用请求获取对应参数，然后通过数据库进行修改，操作成功则通过响应重定向到主页面

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    request.getParameter("xxx");

    response.sendRedirect(request.getContextPath() + "/xxx");

  • Session&Cookie 实现的逻辑

    1. 我们配置了欢迎页，优先级要高于 index.jsp，所以先走 WelcomeServlet
    2. WelcomeServlet 中只进行登录状态验证，设置 Session 和 Cookie 要到 UserServlet 中，即用户登录并选择免登录才设置
    3. 添加了过滤器 LoginCheckFilter，在直接请求学生管理相关路径时，会判断登陆状态