IDEA中WEB项目CURD

梦里梦外; 2024-04-18 15:22 40阅读 0赞

**创建web项目可以参考一下**

*  [**IDEA快速创建web项目**][IDEA_web]

效果图：  
![在这里插入图片描述][20190911132227340.gif]

先看下，项目结构：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mjc0MDUzMA_size_16_color_FFFFFF_t_70]

**步骤：**

1.  创建数据库表
2.  创建包结构
3.  导入所需jar包
4.  配置数据库，获取连接
5.  实现CURD

## 1.创建数据库表 ##

/*
    Navicat MySQL Data Transfer
    
    Source Server         : localhost
    Source Server Version : 50527
    Source Host           : localhost:3306
    Source Database       : ml
    
    Target Server Type    : MYSQL
    Target Server Version : 50527
    File Encoding         : 65001
    
    Date: 2019-09-08 21:51:55
    */
    
    SET FOREIGN_KEY_CHECKS=0;
    
    -- ----------------------------
    -- Table structure for student
    -- ----------------------------
    DROP TABLE IF EXISTS `student`;
    CREATE TABLE `student` (
      `id` int(11) NOT NULL AUTO_INCREMENT,
      `name` varchar(30) DEFAULT NULL,
      `age` int(11) DEFAULT NULL,
      `address` varchar(50) DEFAULT NULL,
      PRIMARY KEY (`id`),
      KEY `index_name` (`age`,`name`,`address`) USING BTREE
    ) ENGINE=InnoDB AUTO_INCREMENT=16 DEFAULT CHARSET=utf8;
    
    -- ----------------------------
    -- Records of student
    -- ----------------------------
    INSERT INTO `student` VALUES ('6', '阿萨德', '12', '德国');
    INSERT INTO `student` VALUES ('1', '张三', '18', '中国');
    INSERT INTO `student` VALUES ('3', '王五', '18', '日本');
    INSERT INTO `student` VALUES ('2', '李四', '19', '香港');
    INSERT INTO `student` VALUES ('4', '赵六', '19', '韩国');
    INSERT INTO `student` VALUES ('5', '孙悟空', '88', '花果山');

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mjc0MDUzMA_size_16_color_FFFFFF_t_70 1]

## 2.创建包结构 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mjc0MDUzMA_size_16_color_FFFFFF_t_70 2]

创建`Student`实体类：

public class Student{
        private Integer id;
        private String name;
        private Integer age;
        private String address;
    
        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 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;
        }
    }

在`web`包下，点击New->Servlet，创建`StudentServlet`  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mjc0MDUzMA_size_16_color_FFFFFF_t_70 3]

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mjc0MDUzMA_size_16_color_FFFFFF_t_70 4]

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mjc0MDUzMA_size_16_color_FFFFFF_t_70 5]  
接着，创建`StudentService`和`StudentDao`，结构如下：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mjc0MDUzMA_size_16_color_FFFFFF_t_70 6]

## 3.导入所需jar包 ##

[**点击下载：web常用jar包**][web_jar]

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mjc0MDUzMA_size_16_color_FFFFFF_t_70 7]  
接着在`File`里选择`Project Structure`  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mjc0MDUzMA_size_16_color_FFFFFF_t_70 8]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mjc0MDUzMA_size_16_color_FFFFFF_t_70 9]  
接着选择`Libraries`，如图：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mjc0MDUzMA_size_16_color_FFFFFF_t_70 10]  
进入界面，选择所有jar包，一直下一步即可![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mjc0MDUzMA_size_16_color_FFFFFF_t_70 11]

## 4. 配置数据库，获取连接 ##

在`src`目录下创建`DBConfig.properties`文件，加入以下配置

driver: com.mysql.jdbc.Driver
    url: jdbc:mysql://localhost:3306/ml?characterEncoding=UTF8&serverTimezone=UTC
    username: root
    password: 123456

结构如下图：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mjc0MDUzMA_size_16_color_FFFFFF_t_70 12]

在`utils`包下创建`JdbcConnection`

import java.io.IOException;
    import java.sql.Connection;
    import java.sql.DriverManager;
    import java.sql.SQLException;
    import java.util.Properties;
    
    public class JdbcConnection {
        public Connection getConnection(){
    
            String driver = null;
            String url = null;
            String user = null;
            String psd = null;
            Connection conn = null;
    
            Properties pro = new Properties();    //新建一个properties实例，用于从DBConfig中拿到连接参数。
            try {
                pro.load(this.getClass().getClassLoader().getResourceAsStream("DBConfig.properties")); //加载DBConfig文件。
                driver = pro.getProperty("driver");
                url = pro.getProperty("url");
                user = pro.getProperty("username");
                psd = pro.getProperty("password");
            } catch (IOException e) {
                e.printStackTrace();
            }
    
            try {
                Class.forName(driver);   //加载jdbc驱动
            } catch (ClassNotFoundException e) {
                e.printStackTrace();
            }
    
            try {
                conn = DriverManager.getConnection(url,user,psd);  //获取数据库连接
                conn.setAutoCommit(false);
                return conn;       //返回一个数据库连接。
            } catch (SQLException e) {
                e.printStackTrace();
            }
    
            return null;
        }
    
    
    
    }

## 5. 实现CURD ##

**需求一：查询所有学生信息**

1.在`web.xml`中配置`servlet`映射路径

<servlet>
            <servlet-name>student</servlet-name>
            <servlet-class>com.tt.web.StudentServlet</servlet-class>
        </servlet>
        
        <servlet-mapping>
            <servlet-name>student</servlet-name>
            <url-pattern>/student</url-pattern> 
        </servlet-mapping>

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mjc0MDUzMA_size_16_color_FFFFFF_t_70 13]

2.修改`index.jsp`  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mjc0MDUzMA_size_16_color_FFFFFF_t_70 14]

3.在`WEB-INF`包下创建`student`包，student包下创建`list.jsp`，结构如下：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mjc0MDUzMA_size_16_color_FFFFFF_t_70 15]

4.修改`list.jsp`

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mjc0MDUzMA_size_16_color_FFFFFF_t_70 16]

5.修改`StudentServlet`

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mjc0MDUzMA_size_16_color_FFFFFF_t_70 17]

6.修改`StudentService`

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mjc0MDUzMA_size_16_color_FFFFFF_t_70 18]

7.修改`StudentDao`

package com.tt.dao;
    
    import com.tt.pojo.Student;
    import com.tt.utils.JdbcConnection;
    
    import java.sql.Connection;
    import java.sql.PreparedStatement;
    import java.sql.ResultSet;
    import java.sql.SQLException;
    import java.util.ArrayList;
    import java.util.List;
    
    public class StudentDao {
        public List<Student> findAll() {
    
            ArrayList<Student> list = new ArrayList<>();
            try {
                JdbcConnection jdbcConnection = new JdbcConnection();//创建Jdbc对象
                Connection con = jdbcConnection.getConnection();//获取连接
                String sql = "select * from student";
                PreparedStatement ps = con.prepareStatement(sql);
                ResultSet rs = ps.executeQuery();
                while (rs.next()) {
                    Student student = new Student();
                    student.setId(rs.getInt("id"));
                    student.setName(rs.getString("name"));
                    student.setAge(Integer.valueOf(rs.getString("age")));
                    student.setAddress(rs.getString("address"));
                    list.add(student);
                }
                con.commit();//提交事务
                con.close();//关闭连接
            } catch (SQLException e) {
                e.printStackTrace();
            }
            return list;
        }
    }

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mjc0MDUzMA_size_16_color_FFFFFF_t_70 19]

8.启动tomcat

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mjc0MDUzMA_size_16_color_FFFFFF_t_70 20]  
9.访问`http://localhost:8080/`  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mjc0MDUzMA_size_16_color_FFFFFF_t_70 21]  
10.点击：查询所有学生信息

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mjc0MDUzMA_size_16_color_FFFFFF_t_70 22]

**需求二：（添加、修改、删除） 学生信息**

首先拿到需求后，先进行分析：

*  页面上需要添加一个保存按钮，并且跳转到添加页面
 *  后台接收请求，处理请求（一般情况，**用户添加完数据，是需要展示出来的**，所以**重新调用查询所有学生**的方法即可）

1.修改list页面，添加保存按钮

<%--
      Created by IntelliJ IDEA.
      User: Administrator
      Date: 2019/9/8
      Time: 22:35
      To change this template use File | Settings | File Templates.
    --%>
    <%@ 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>
    
    <table align="center" border="1px" >
        <tr>
            <th>姓名</th>
            <th>年龄</th>
            <th>地址</th>
            <th>操作|
            <a href="${pageContext.request.contextPath}/student?method=toAddStudentUI">添加</a>
            </th>
        </tr>
        <c:if test="${empty list}">
            <tr>
                <td>没有学生数据</td>
            </tr>
        </c:if>
        <c:if test="${!empty list}">
            <c:forEach items="${list}" var="item">
                <tr>
                    <td>${item.name}</td>
                    <td>${item.age}</td>
                    <td>${item.address}</td>
                    <td>
                        <a href="${pageContext.request.contextPath}/student?method=toUpdateUI&id=${item.id}">修改</a>
                        |
                        <a href="${pageContext.request.contextPath}/student?method=delete&id=${item.id}">删除</a>
                    </td>
                </tr>
            </c:forEach>
        </c:if>
    
    </table>
    
    </body>
    </html>

2.添加`add.jsp`页面

<%--
      Created by IntelliJ IDEA.
      User: Administrator
      Date: 2019/9/9
      Time: 0:01
      To change this template use File | Settings | File Templates.
    --%>
    <%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <html>
    <head>
        <title>Title</title>
    </head>
    <body>
    
    <form action="${pageContext.request.contextPath}/student" method="post">
        <input type="hidden" name="method" value="addStudent"> <%--隐藏域，将所需参数带过去--%>
        <table align="center" border="1px">
            <tr>
                <th>姓名</th>
                <td>
                    <input type="text" name="name" >
                </td>
            </tr>
            <tr>
                <th>年龄</th>
                <td>
                    <input type="text" name="age">
                </td>
            </tr>
            <tr>
                <th>地址</th>
                <td>
                    <input type="text" name="address">
                </td>
            </tr>
            <tr>
                <td align="center" colspan="2">
                    <input type="submit" value="保存">
                </td>
            </tr>
        </table>
    </form>
    
    </body>
    </html>

3.添加`update.jsp`页面

<%--
      Created by IntelliJ IDEA.
      User: Administrator
      Date: 2019/9/9
      Time: 0:28
      To change this template use File | Settings | File Templates.
    --%>
    <%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <html>
    <head>
        <title>Title</title>
    </head>
    <body>
    <form action="${pageContext.request.contextPath}/student" method="post">
        <input type="hidden" name="method" value="upStudent"> <%--隐藏域，将所需参数带过去--%>
        <input type="hidden" name="id" value="${student.id}"> <%--隐藏域，将所需参数带过去--%>
        <table align="center" border="1px">
            <tr>
                <th>姓名</th>
                <td>
                    <input type="text" name="name" value="${student.name}">
                </td>
            </tr>
            <tr>
                <th>年龄</th>
                <td>
                    <input type="text" name="age" value="${student.age}">
                </td>
            </tr>
            <tr>
                <th>地址</th>
                <td>
                    <input type="text" name="address" value="${student.address}">
                </td>
            </tr>
            <tr>
                <td>
                    <input type="submit" value="修改">
                </td>
            </tr>
        </table>
    </form>
    </body>
    </html>

添加完后，结构如下：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mjc0MDUzMA_size_16_color_FFFFFF_t_70 23]

4.修改`servlet`

package com.tt.web;
    
    import com.tt.pojo.Student;
    import com.tt.service.StudentService;
    
    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 = "StudentServlet")
    public class StudentServlet extends HttpServlet {
    
    
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            //设置编码
            response.setContentType("text/html;charset=utf-8");
            request.setCharacterEncoding("UTF-8");
            String method = request.getParameter("method"); //获取到method，判断执行哪个方法
            if ("addStudent".equals(method)) {
                addStudent(request, response);
            } else if ("upStudent".equals(method)) {
                upStudent(request,response);
            }
    
        }
    
    
    
        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            //设置编码
            response.setContentType("text/html;charset=utf-8");
            request.setCharacterEncoding("UTF-8");
            String method = request.getParameter("method"); //获取到method，判断执行哪个方法
            if ("findAll".equals(method)) {
                findAll(request, response);
            } else if ("toAddStudentUI".equals(method)) {
                toAddStudentUI(request,response);
            }else if ("toUpdateUI".equals(method)) {
                toUpdateUI(request,response);
            } else if ("delete".equals(method)) {
                delete(request,response);
    
            }
    
        }
    
        /**
         * 删除学生信息
         * @param request
         * @param response
         */
        private void delete(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            Integer id = Integer.valueOf(request.getParameter("id"));
            StudentService studentService = new StudentService();
            int i =studentService.delete(id);
            if (i!=0) {
                List<Student> list = studentService.findAll();
                request.setAttribute("list",list);
                request.getRequestDispatcher("WEB-INF/student/list.jsp").forward(request,response);
            }
        }
    
        /**
         * 修改学生信息
         * @param request
         * @param response
         */
        private void upStudent(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            Student student = new Student();
            student.setId(Integer.valueOf(request.getParameter("id")));
            student.setName(request.getParameter("name"));
            student.setAge(Integer.valueOf(request.getParameter("age")));
            student.setAddress(request.getParameter("address"));
            StudentService studentService = new StudentService();
            int i =studentService.update(student);
            if (i!=0) {
                List<Student> list = studentService.findAll();
                request.setAttribute("list",list);
                request.getRequestDispatcher("WEB-INF/student/list.jsp").forward(request,response);
            }
        }
    
        /**
         * 添加学生信息
         * @param request
         * @param response
         */
        private void addStudent(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            Student student = new Student();
            student.setName(request.getParameter("name"));
            student.setAge(Integer.valueOf(request.getParameter("age")));
            student.setAddress(request.getParameter("address"));
            StudentService studentService = new StudentService();
            int i =studentService.save(student);
            if (i!=0) {
                List<Student> list = studentService.findAll();
                request.setAttribute("list",list);
                request.getRequestDispatcher("WEB-INF/student/list.jsp").forward(request,response);
            }
        }
    
    
    
        /**
         * 到修改页面
         * @param request
         * @param response
         */
        private void toUpdateUI(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            StudentService studentService = new StudentService();
            Student student = studentService.findId(Integer.valueOf(request.getParameter("id")));
            request.setAttribute("student",student);
            request.getRequestDispatcher("WEB-INF/student/update.jsp").forward(request,response);
        }
    
        /**
         * 到添加学生的页面
         * @param request
         * @param response
         */
        private void toAddStudentUI(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            request.getRequestDispatcher("WEB-INF/student/add.jsp").forward(request,response);
        }
    
        /**
         * 查询所有学生信息
         *
         * @param request
         * @param response
         */
        private void findAll(HttpServletRequest request, HttpServletResponse response) {
            try {
                StudentService studentService = new StudentService();
                List<Student> list = studentService.findAll();
                request.setAttribute("list", list);//放入request域中
                request.getRequestDispatcher("WEB-INF/student/list.jsp").forward(request, response);//请求转发到WEB-INF/student/list.jsp页面并展示
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    
    
    }

5.修改`StudentService`

package com.tt.service;
    
    import com.tt.dao.StudentDao;
    import com.tt.pojo.Student;
    
    import java.util.List;
    
    public class StudentService {
        public List<Student> findAll() {
            StudentDao studentDao = new StudentDao();
            return studentDao.findAll();
        }
    
        public int save(Student student) {
            StudentDao studentDao = new StudentDao();
            return studentDao.save(student);
        }
    
        public Student findId(Integer id) {
            StudentDao studentDao = new StudentDao();
            return studentDao.findId(id);
        }
    
        public int update(Student student) {
            StudentDao studentDao = new StudentDao();
            return studentDao.update(student);
    
        }
    
        public int delete(Integer id) {
            StudentDao studentDao = new StudentDao();
            return studentDao.delete(id);
        }
    }

6.修改`StudentDao`

package com.tt.dao;
    
    import com.tt.pojo.Student;
    import com.tt.utils.JdbcConnection;
    
    import java.sql.*;
    import java.util.ArrayList;
    import java.util.List;
    
    public class StudentDao {
        public Student findId(Integer id) {
            Student student = new Student();
            try {
    
    //            Class.forName("com.mysql.jdbc.Driver"); //加载驱动
    //            Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/ml","root", "123456"); //获取连接
                JdbcConnection jdbcConnection = new JdbcConnection();//创建Jdbc对象
                Connection con = jdbcConnection.getConnection();//获取连接
                String sql = "select * from student where id=?";
                PreparedStatement ps = null;
                ps = con.prepareStatement(sql);
                ps.setInt(1, Integer.valueOf(id));
                ResultSet rs = ps.executeQuery();
                while (rs.next()) {
                    student.setId(rs.getInt("id"));
                    student.setName(rs.getString("name"));
                    student.setAge(Integer.valueOf(rs.getString("age")));
                    student.setAddress(rs.getString("address"));
    
                }
                con.close();//关闭连接
            } catch (Exception e) {
                e.printStackTrace();
            }
    
            return student;
        }
    
        public List<Student> findAll() {
    
            ArrayList<Student> list = new ArrayList<>();
            try {
                JdbcConnection jdbcConnection = new JdbcConnection();//创建Jdbc对象
                Connection con = jdbcConnection.getConnection();//获取连接
                String sql = "select * from student";
                PreparedStatement ps = con.prepareStatement(sql);
                ResultSet rs = ps.executeQuery();
                while (rs.next()) {
                    Student student = new Student();
                    student.setId(rs.getInt("id"));
                    student.setName(rs.getString("name"));
                    student.setAge(Integer.valueOf(rs.getString("age")));
                    student.setAddress(rs.getString("address"));
                    list.add(student);
                }
                con.commit();//提交事务
                con.close();//关闭连接
            } catch (SQLException e) {
                e.printStackTrace();
            }
            return list;
        }
    
        public int save(Student student) {
            Connection con = new JdbcConnection().getConnection();
            String sql = "insert into student(name,age,address) values(?,?,?)";
            int i = 0;
            try {
                PreparedStatement ps = con.prepareStatement(sql);
                ps.setString(1, student.getName());
                ps.setInt(2, student.getAge());
                ps.setString(3, student.getAddress());
                i = ps.executeUpdate();
                con.commit();
                con.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
    
            return i;
        }
    
        public int update(Student student) {
            Connection con = new JdbcConnection().getConnection();
            String sql = "update student set name=? ,age=? , address=? where id = ?";
            int i = 0;
            try {
                PreparedStatement ps = con.prepareStatement(sql);
                ps.setString(1, student.getName());
                ps.setInt(2, student.getAge());
                ps.setString(3, student.getAddress());
                ps.setInt(4, student.getId());
                i = ps.executeUpdate();
                con.commit();
                con.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
    
            return i;
        }
    
        public int delete(Integer id) {
            Connection con = new JdbcConnection().getConnection();
            String sql = "delete from student where id= ? ";
            int i = 0;
            try {
                PreparedStatement ps = con.prepareStatement(sql);
                ps.setInt(1,id);
                i = ps.executeUpdate();
                con.commit();
                con.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
    
            return i;
        }
    }

完整的结构：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mjc0MDUzMA_size_16_color_FFFFFF_t_70 24]

当然看到这里，有人肯定会说，你应该把StudentDao层中的关流，放到`finally`中做，是的，的确应该放在`finally`里，这里只是给大家提供**一种思路**，细节可能会遗漏！

## 问答题： ##

1.为什么`doGet`和`doPost`中都要写方法，不能再一个里面写吗?

> 答：因为表单提交是post方式的，所以要分开写

2.为什么CRUD中的路径都是`/student`呢？

> 答：因为每个servlet只能配置一个路径；假如有一百张表，每张表中的CRUD是必不可少的，那么需要配置至少400个`servlet`，此时起名字应该都不知道怎么起了吧！！！！，所以建议一个表中的CURD用`配置一个路径`，具体`通过一些标识来区分`  
> 例如：我是根据method中的参数来区分的

3.为什么没有使用接口呢？

> 答：因为只是提供一种思路。工作中肯定要用接口，实现类的。

4.以上代码还能再做优化吗?

> 答：当然可以

以上有写的不对的地方，请及时通知博主，谢谢！！！

[IDEA_web]: https://blog.csdn.net/weixin_42740530/article/details/100638662
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