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java之jsp

发表于 更新于 分类于 阅读次数： Valine：

说明

  • 上篇主要搭建了servlet，本次主要加入jsp的应用，功能包括增删改查
  • 本次java 版本
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C:\Users\Administrator>java -version
java version "1.8.0_381"
Java(TM) SE Runtime Environment (build 1.8.0_381-b09)
Java HotSpot(TM) 64-Bit Server VM (build 25.381-b09, mixed mode)

简单实例

  • webapp下新增index.jsp
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<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>主页</title>
</head>
<body>
    <%
	    String user=(String)session.getAttribute("user");
        if (user != null) {
            // 用户已登录
             out.println("<a href=\"homePage.jsp\">");
             out.println("登录成功主页");
             out.println("</a>");
        } else {
            // 用户未登录
            out.println("<a href=\"login.jsp\">");
            out.println("登录界面");
            out.println("</a>");
        }
    %>
</body>
</html>
  • 当sesssion数据不存在，可点击进入登录界面

image-20231201173302810

  • webapp/login.jsp
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<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>登录</title>
</head>
<body>
    <h1>登录</h1>
    <form action="login" method="post">
        <label for="username">用户名：</label>
        <input type="text" id="username" name="username" required><br><br>
        <label for="password">密码：</label>
        <input type="password" id="password" name="password" required><br><br>
        <input type="submit" value="登录">
    </form>
</body>
</html>
  • 登录的servlet
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package xyz.shi.servlet;
...
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpSession;

@WebServlet("/login")
public class LoginServlet extends HttpServlet{
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String username = request.getParameter("username");
        String password = request.getParameter("password");

        // 验证用户名和密码
        if (username.equals("admin") && password.equals("123456")) {
            // 登录成功，创建会话
            HttpSession session = request.getSession();
            session.setAttribute("username", username);
            response.sendRedirect("homePage.jsp");
        } else {
            // 登录失败，返回登录页面
            request.setAttribute("error", "用户名或密码错误");
            request.getRequestDispatcher("login.jsp").forward(request, response);
        }
    }
}
  • webapp/homePage.jsp
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<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>主页</title>
</head>
<body>
    <h1>欢迎登录，${username}！</h1>
    <a href="logout">注销</a>
</body>
</html>
  • 注销的Servlet
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package xyz.shi.servlet;

...
@WebServlet("/logout")
public class LogoutServlet extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        HttpSession session = request.getSession();
        session.invalidate();
        response.sendRedirect("login.jsp");
    }
}

image-20231201173645669

结合jdbc

  • 基础知识参考这篇文章

  • 首先pom.xml中加入本次需要的依赖文件

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<dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.13</version>
        </dependency>
        <dependency>
            <groupId>commons-dbutils</groupId>
            <artifactId>commons-dbutils</artifactId>
            <version>1.5</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/javax.servlet/jstl -->
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>jstl</artifactId>
            <version>1.2</version>
        </dependency>

jstl主要是在jsp中使用的标签语法

三层架构

  • 表示层：主要是指与用户交互的界面。用于接收用户输入的数据和显示处理后用户需要的数 据。

  • 业务逻辑层：UI层（表示）和DAL层（数据访问）之间的桥梁。实现业务逻辑。业务逻辑具体包含：验证、计算、业务规则等等。

  • 数据访问层：与数据库打交道。主要实现对数据的增、删、改、查。将存储在数据库中的数据提交给业务层，同时将业务层处理的数据保存到数据库。

  • 实体层：它不属于三层中的任何一层，贯穿于三层，在三层之间传递数据;

实体层

  • xyz.shi.entity.User
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package xyz.shi.entity;
public class User {
    private int id;
    private String name;
    private String password;
    public int getId() {
        return id;
    }
    // 因为QueryRunner创建Bean对象的过程使用的是newInstance()方法，该方法只能调用无参构
    public  User () {

    }
    public User(int id,String name, String password) {
        this.name = name;
        this.id = id;
        this.password = password;
    }
    public void setId(int id) { this.id = id;}
    public String getName() { return name;}
    public void setName(String name) { this.name = name;}
    public void setPassword(String password) {this.password = password;}
    public String getPassword() {return password;}

}

数据访问层

  • 分为接口和实现接口，代码放在xyz.shi.dao 包下

  • 接口层xyz.shi.dao.UserDao

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package xyz.shi.dao;

import xyz.shi.entity.User;

import java.sql.SQLException;
import java.util.List;

public interface UserDao {
    //返回所有对象
    List<User> queryAllList(String sql);
    // 查找多条记录
    List<User> queryList(String sql,Object ...params);
    // 查找一条记录
    User queryOne(String sql, Object... parameters);
    // 修改(删除)一条记录
    int update(String sql, Object... parameters) ;
}

  • 实现接口层xyz.shi.dao.impl.UserDaoImpl
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package xyz.shi.dao.impl;

import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanHandler;
import org.apache.commons.dbutils.handlers.BeanListHandler;
import xyz.shi.dao.UserDao;
import xyz.shi.entity.User;

import java.sql.Connection;
import java.sql.SQLException;
import java.util.List;
import xyz.shi.util.jdbcUtil;
public class UserDaoImpl implements UserDao {
    private QueryRunner qr =  new QueryRunner();
    // 返回所有对象
    @Override
    public List<User> queryAllList(String sql) {
        Connection connection = null;
        try {
            connection =jdbcUtil.getConnection();
            return qr.query(connection, sql, new BeanListHandler<User>(User.class));
        } catch (SQLException e) {
            throw new RuntimeException(e);
        } finally {
            jdbcUtil.closeResource(null,null, connection);
        }
    }
    // 返回多个对象(即查询的结果是多行)
    @Override
    public List<User> queryList(String sql, Object... params) {
        Connection connection = null;
        try {
            connection =jdbcUtil.getConnection();
            return qr.query(connection, sql, new BeanListHandler<User>(User.class), params);
        } catch (SQLException e) {
            throw new RuntimeException(e);
        } finally {
            jdbcUtil.closeResource(null,null, connection);
        }
    }
    // 查询单行结果
    @Override
    public User queryOne(String sql, Object... parameters) {
        Connection connection = null;

        try {
             connection =jdbcUtil.getConnection();
            return qr.query(connection, sql, new BeanHandler<User>(User.class), parameters);

        } catch (SQLException e) {
            throw new RuntimeException(e);
        } finally {
            jdbcUtil.closeResource(null,null, connection);
        }

    }
    // 修改(增删改通用)
    @Override
    public int update(String sql, Object... parameters) {
        Connection connection = null;
        try {
            connection =jdbcUtil.getConnection();
            return  qr.update(connection,sql,parameters);
        } catch (SQLException e) {
            throw new RuntimeException(e);
        } finally {
        jdbcUtil.closeResource(null,null, connection);
    }
    }
}

业务逻辑层

  • 分为接口和实现接口，代码放在xyz.shi.service 包下

  • 接口层xyz.shi.service.UserService

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package xyz.shi.service;
import xyz.shi.entity.User;
import java.util.List;
public interface UserService {
    //根据userId查询一个user
    User getUser(String id);
    //根据name和password查询一个user
    Boolean ableLogin (String name , String password);
    //查找多条user对象
    List<User> getUserList(Object... parameters);
    //查找所有user对象
    List<User> getAllUser();
    //增加一个user
    int addUser(Object... parameters);
    //删除一个user
    int deleteUser(int userId);
    //修改一个user的信息
    int updateUser(Object... parameters);
}

  • xyz.shi.service.impl.UserServiceImpl 实现接口，这里就是编写具体的逻辑
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package xyz.shi.service.impl;

import xyz.shi.dao.UserDao;
import xyz.shi.dao.impl.UserDaoImpl;
import xyz.shi.entity.User;
import xyz.shi.service.UserService;

import java.sql.SQLException;
import java.util.List;

public class UserServiceImpl implements UserService {
    //创建UserDaoImpl对象
    private UserDao userDao = new UserDaoImpl();
    //查询所有
    @Override
    public List<User> getAllUser() {
        String sql ="select * from `users`";
        try {
            return  userDao.queryAllList(sql);
        } catch (Exception e) {
            System.out.println(e);
            return null;
        }
    }
    //根据userId查询一个user
    @Override
    public User getUser(String userId) {
        String sql = "select * from `users` where id = ? ";
        try {
            return  userDao.queryOne(sql,userId);
        } catch (Exception e) {
            System.out.println(e);
            return null;
        }
    }
    //根据userId和password查询一个user
    @Override
    public Boolean ableLogin (String name , String password) {
        String sql ="select * from `users` where name = ? and password = ? ";
        User user = userDao.queryOne(sql, name, password);

        return user != null ? true : false;

    }
    //根据条件查询多个user
    @Override
    public List<User> getUserList(Object... parameters) {
        String sql ="select * from `users` where ? = ? ";
        try {
            return  userDao.queryList(sql,parameters);
        } catch (Exception e) {
            System.out.println(e);
            return null;
        }
    }
    //增加一个user
    @Override
    public int addUser(Object... parameters) {
        String sql ="insert into `users` (name, password) values (?, ?)";
        return  userDao.update(sql, parameters);
    }
    //删除一个user
    @Override
    public int deleteUser(int userId) {
        String sql ="delete from `users` where id = ? ";
        return  userDao.update(sql,userId);
    }
    //修改一个user的信息
    @Override
    public int updateUser(Object... parameters) {
        String sql ="update `users` set name = ?,password = ? where id = ? ";
        return  userDao.update(sql,parameters);
    }

}

表示层

  • 也就是用户界面层

  • xyz.shi.servlet 层，主要放jsp文件传过来的数据，然后把服务器数据传给jsp页面

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package xyz.shi.servlet;

import xyz.shi.entity.User;
import xyz.shi.service.UserService;
import xyz.shi.service.impl.UserServiceImpl;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.List;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpSession;

@WebServlet("/login")
public class LoginServlet extends HttpServlet{
    // 注意这里get的写法，当其他页面新增或者修改成功后，跳转到/login页面，然后自动读取用户列表数据
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String session = (String) req.getSession().getAttribute("username");
        if (session != null) {
            UserService userService = new UserServiceImpl();
            List<User> users = userService.getAllUser();
            req.setAttribute("userList", users);
            req.getRequestDispatcher("homePage.jsp").forward(req, resp);;

        }
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        UserService userService = new UserServiceImpl();
        String username = request.getParameter("username");
        String password = request.getParameter("password");
         boolean login = userService.ableLogin(username, password);
        // 验证用户名和密码
        if (login) {
            // 登录成功，创建会话
            HttpSession session = request.getSession();
            List<User> users = userService.getAllUser();
            request.setAttribute("userList", users);

            session.setAttribute("username", username);
            System.out.println("登录成功");
            request.getRequestDispatcher("homePage.jsp").forward(request, response);;
        } else {
            // 登录失败，返回登录页面
            System.out.println("登录失败");
            request.setAttribute("error", "用户名或密码错误");
            request.getRequestDispatcher("login.jsp").forward(request, response);

        }
    }
}
  • 默认打开的是index.jsp界面
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<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>主页</title>
</head>
<body>
    <%
	    String user=(String)session.getAttribute("username");
        if (user != null) {
            // 用户已登录
             out.println("<a href=\"homePage.jsp\">");
             out.println("登录成功主页");
             out.println("</a>");
        } else {
            // 用户未登录
            out.println("<a href=\"login.jsp\">");
            out.println("登录界面");
            out.println("</a>");
        }
    %>
</body>
</html>
  • 登录界面login.jsp
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<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>登录</title>
</head>
<body>
    <h1>登录</h1>
    <form action="login" method="post">
        <label for="username">用户名：</label>
        <input type="text" id="username" name="username" required><br><br>
        <label for="password">密码：</label>
        <input type="password" id="password" name="password" required><br><br>
        <input type="submit" value="登录">
    </form>
</body>
</html>
  • 登录后的界面homepage.jsp
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><!DOCTYPE html>
<%@ page contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>

<html>
<head>
    <meta charset="UTF-8">
    <title>主页</title>
</head>
<body>
    <h1>欢迎登录，${username}！</h1>
    <a href="add.jsp">添加</a>
    <table>
        <tr>
            <td>id</td>
            <td>用户名</td>
            <td>状态</td>
            <td>操作</td>
        </tr>
        <c:forEach var="item" items="${requestScope.userList}">
                <tr>
                    <td>${item.id}</td>
                    <td>${item.name}</td>
                    <td><a href="userFind?id=${item.id}">修改</a>
            <td><a href="<%=request.getContextPath()%>/userDel?id=${item.id}">删 除</a></td>
                </tr>
            </c:forEach>

    </table>
    <a href="logout">注销</a>
</body>
</html>

登录成功后LoginServlet把用户列表传给了homePage.jsp，后续的修改，删除逻辑也是一样

servlet层

  • 比如下面这是修改用户名
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package xyz.shi.servlet;

import xyz.shi.entity.User;
import xyz.shi.service.UserService;
import xyz.shi.service.impl.UserServiceImpl;
import xyz.shi.utils.GetUsersUtils;

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("/userUpdate")
public class UpdateUserServlet extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        UserService userService = new UserServiceImpl();
        int userId = Integer.parseInt(request.getParameter("id"));
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        User user = new User(userId, username, password);
        int flag = userService.modify(user);
        if (flag > 0) {
            System.out.println("修改数据成功");
            GetUsersUtils.GetUsers(request, response);
        } else {
            // 登录失败，返回登录页面
            System.out.println("修改数据失败");
            request.setAttribute("message", "failed");

        }
    }
}