手把手教你写一个MyBatis入门程序-使用面向对象的思想写一个对用户信息进行增删改查的程序

野性酷女 2024-02-18 13:15 40阅读 0赞

## 手把手教你写一个MyBatis入门程序-使用面向对象的思想写一个对用户信息进行增删改查的程序 ##

### 1.创建文件 ###

这里我就自己命名为：Code\_Book

并在构建系统时选择Maven项目

![image-20231119203808051][]

### 2.引入相关依赖 ###

pom.xml文件

![image-20231119215824234][]

<?xml version="1.0" encoding="UTF-8"?>
    <project xmlns="http://maven.apache.org/POM/4.0.0"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
        <modelVersion>4.0.0</modelVersion>
    
        <groupId>org.example</groupId>
        <artifactId>Code_Book</artifactId>
        <version>1.0-SNAPSHOT</version>
    
        <properties>
            <maven.compiler.source>17</maven.compiler.source>
            <maven.compiler.target>17</maven.compiler.target>
            <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        </properties>
        
        
        
        <dependencies>
            
            <dependency>
                <groupId>org.mybatis</groupId>
                <artifactId>mybatis-parent</artifactId>
                <version>37</version>
            </dependency>
            
            
            <dependency>
                <groupId>junit</groupId>
                <artifactId>junit</artifactId>
                <version>4.13.2</version>
                <scope>test</scope>
            </dependency>
        </dependencies>
    
    </project>

### 3.创建数据库 ###

（1）新建数据库

![image-20231119211951990][]

（2）新建一个user表（记得主键自增）

![image-20231119212356857][]

（3）输入数据

![image-20231119212526712][]

### 4.创建数据库连接信息配置文件 ###

在resources目录下直接创建db.properties文件

mysql.driver = com.mysql.cj.jdbc.Driver
    mysql.url = jdbc:mysql://localhost:3306/mybatis?serverTimezone=UTC&characterEncoding=utf8&useUnicode=true&useSSL=false
    mysql.username = root
    mysql.password = 123456

### 5.创建Mybatis的核心配置文件 ###

在resources目录下直接创建mybatis-config.xml文件

<?xml version="1.0" encoding="UTF-8" ?>
    <!DOCTYPE configuration
            PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
            "https://mybatis.org/dtd/mybatis-3-config.dtd">
    <configuration>
        
        <properties resource="db.properties"/>
        
        <environments default="development">
            <environment id="development">
                <transactionManager type="JDBC"/>
                <dataSource type="POOLED">
                    <property name="driver" value="${mysql.driver}"/>
                    <property name="url" value="${mysql.url}"/>
                    <property name="username" value="${mysql.username}"/>
                    <property name="password" value="${mysql.password}"/>
                </dataSource>
            </environment>
        </environments>
    </configuration>

### 6.创建实体类（POJO实体） ###

（1）先新建一个软件包,名为：com

（2）在com中建立一个包为Study\_2

（3）创建一个pojo包；在包中，新建一个实体类，名为User。

![image-20231121073738208][]

package com.Study_2.pojo;
    
    public class User {
    
        private int uid; //用户id
        private String uname; //用户姓名
        private int uage; //用户年龄
    
    
        //写出Getter方法和Setter方法
    
        public int getUid() {
            return uid;
        }
    
        public void setUid(int uid) {
            this.uid = uid;
        }
    
        public String getUname() {
            return uname;
        }
    
        public void setUname(String uname) {
            this.uname = uname;
        }
    
        public int getUage() {
            return uage;
        }
    
        public void setUage(int uage) {
            this.uage = uage;
        }
    
        @Override
        public String toString() {
            return "User{" +
                    "uid=" + uid +
                    ", uname='" + uname + '\'' +
                    ", uage=" + uage +
                    '}';
        }
    }

### 7.创建映射文件 ###

（1）在resources目录中创建一个mapper文件夹

（2）在mapper文件夹中创建映射文件，名为：UserMapper\_Study\_2.xml

<?xml version="1.0" encoding="UTF-8" ?>
    <!DOCTYPE mapper
            PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
            "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
    
    <mapper namespace="com.Study_2.pojo.User">
        
    
        
        <select id="findById" parameterType="int" resultType="com.Study_2.pojo.User">
            select * from users where uid = #{id}
        </select>
        
        <insert id="addUser" parameterType="com.Study_2.pojo.User">
            insert into users(uid,uname,uage) values (#{uid},#{uname},#{uage})
        </insert>
        
        <update id="updateUser" parameterType="com.Study_2.pojo.User">
            update users set uname = #{uname},uage = #{uage} where uid = #{uid}
        </update>
        
        <delete id="deleteUser" parameterType="Integer">
            delete from users where uid=#{uid}
        </delete>
    
    </mapper>

![image-20231121073826695][]

### 8.修改mybatis-config.xml文件 ###

即加mapping文件路径配置

完整的mybatis-config.xml文件如下：

### 9.编写工具类 ###

在Study\_2包中新建一个util包；

在包中创建一个MybatisUtil类。

package com.Study_2.util;
    
    import org.apache.ibatis.io.Resources;
    import org.apache.ibatis.session.SqlSession;
    import org.apache.ibatis.session.SqlSessionFactory;
    import org.apache.ibatis.session.SqlSessionFactoryBuilder;
    
    import java.io.IOException;
    import java.io.Reader;
    
    public class MybatisUtil {
    
        // 静态变量，用于保存共享的 SqlSessionFactory 实例
        private static SqlSessionFactory sqlSessionFactory;
    
        // 静态块，在类加载时执行
        static {
            try {
                // 指定 MyBatis 的配置文件
                String resources = "mybatis-config.xml";
    
                // 将配置文件作为 Reader 读取
                Reader reader = Resources.getResourceAsReader(resources);
    
                // 使用 MyBatis 配置构建 SqlSessionFactory
                sqlSessionFactory  = new SqlSessionFactoryBuilder().build(reader);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    
        // 打开一个新的 SqlSession 实例的方法
        public static SqlSession openSession() {
            return sqlSessionFactory.openSession();
        }
    
        // 关闭 SqlSession 实例的方法
    //    public static void closeSession(SqlSession session) {
    //        if (session != null) {
    //            session.close();
    //        }
    //    }
    }

### 10.编写测试类 ###

在com.Study\_2中创建Test包

然后在Test包中创建Test类

package com.Study_2.test;
    
    import com.Study_2.pojo.User;
    import com.Study_2.util.MybatisUtil;
    import org.apache.ibatis.session.SqlSession;
    
    public class Test {
        //查
        @org.junit.Test
        public void FindUser(){
            SqlSession session = MybatisUtil.openSession();
                User user = session.selectOne("findById", 2);
                System.out.println(user.toString());
                session.close();
        }
        //增
        @org.junit.Test
        public void AddUserTest(){
            SqlSession session = MybatisUtil.openSession();
            User user = new User();
            user.setUid(6);
            user.setUname("增加张三");
            user.setUage(16);
            int ifadd = session.insert("addUser",user);
            session.commit();
            if(ifadd!=1)
                System.out.println("增加用户失败");
            else
                System.out.println("增加用户成功\n"+user.toString());
            session.close();
        }
        //改
        @org.junit.Test
        public void UpadeteUser(){
            SqlSession session = MybatisUtil.openSession();
            User user = new User();
            user.setUid(1);
            user.setUname("修改后张三");
            user.setUage(66);
            int ifupdate = session.update("updateUser",user);
            session.commit();
            if (ifupdate!=1)
                System.out.println("更新失败");
            else
                System.out.println("更新成功,更新后的用户信息是:\n"+user.toString());
            session.close();
        }
        //删
        @org.junit.Test
        public void DeleteUser(){
            SqlSession session = MybatisUtil.openSession();
            int ifdelete = session.delete("deleteUser",1);
            if (ifdelete!=1)
                System.out.println("删除失败");
            else
                System.out.println("删除成功");
        }
    }

代码的整体结构如下图：

![image-20231121074105928][]

### 11.运行程序 ###

[image-20231119203808051]: https://image.dandelioncloud.cn/pgy_files/images/2024/02/18/c5d2f87514564421880f395785cd6047.png
[image-20231119215824234]: https://image.dandelioncloud.cn/pgy_files/images/2024/02/18/a0ff55b2d3e7444bb304a7cc10a0290a.png
[image-20231119211951990]: https://image.dandelioncloud.cn/pgy_files/images/2024/02/18/7fff6e298be246f3b42cfd349a1e3acb.png
[image-20231119212356857]: https://image.dandelioncloud.cn/pgy_files/images/2024/02/18/54c1ff9dc0aa465eb458a67814a2b237.png
[image-20231119212526712]: https://image.dandelioncloud.cn/pgy_files/images/2024/02/18/65bd8a3b0c3c485db916964941f7019c.png
[image-20231121073738208]: https://image.dandelioncloud.cn/pgy_files/images/2024/02/18/91937e922d4748a3b1788f16e328cc5c.png
[image-20231121073826695]: https://image.dandelioncloud.cn/pgy_files/images/2024/02/18/2ff05067a66b457f87397eff96d8c742.png
[image-20231121074105928]: https://image.dandelioncloud.cn/pgy_files/images/2024/02/18/a23f4183e15e4b11b89d9000cefe5072.png