一个 MyBatis 的完整案例

最新推荐文章于 2025-09-12 20:47:31 发布

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文章标签：

#mybatis #sql #mysql #maven #java #spring #spring boot

以下是一个 MyBatis 的完整案例，实现对一个简单的用户信息表的增、删、改、查操作。

1. 准备工作

数据库准备：创建一个名为 mybatis_demo 的数据库，其中包含一个 users 表，表结构如下：

CREATE TABLE `users` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `username` varchar(50) NOT NULL,
  `password` varchar(50) NOT NULL,
  `email` varchar(100) DEFAULT NULL,
  PRIMARY KEY (`id`)
);

2. 创建项目结构

在 IDE 中创建一个 Maven 项目（这里以 Maven 为例，Gradle 类似），项目结构如下：

mybatis-demo
|-- src
|   |-- main
|   |   |-- java
|   |   |   |-- com
|   |   |   |   |-- example
|   |   |   |   |   |-- dao
|   |   |   |   |   |-- entity
|   |   |   |   |   |-- service
|   |   |   |   |   |-- service.impl
|   |   |   |   |   |-- util
|   |   |   |-- resources
|   |   |       |-- mybatis-config.xml
|   |   |       |-- mapper
|   |-- test
|       |-- java
|           |-- com
|               |-- example
|                   |-- MyBatisDemoApplicationTests.java

3. 配置项目依赖（pom.xml）

<?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>com.example</groupId>
    <artifactId>mybatis-demo</artifactId>
    <version>1.0-SNAPSHOT</version>

    <dependencies>
        <!-- MyBatis 依赖 -->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.9</version>
        </dependency>
        <!-- MySQL 数据库驱动 -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql - connector - java</artifactId>
            <version>8.0.28</version>
        </dependency>
        <!-- Lombok 依赖，用于简化实体类代码 -->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.24</version>
        </dependency>
    </dependencies>
</project>

4. 创建实体类（com.example.entity.User）

package com.example.entity;

import lombok.Data;

@Data
public class User {
    private Integer id;
    private String username;
    private String password;
    private String email;
}

5. 创建数据访问对象（DAO）接口和映射文件

UserDao 接口（com.example.dao.UserDao）

package com.example.dao;

import com.example.entity.User;
import java.util.List;

public interface UserDao {
    User getUserById(int id);
    List<User> getUsers();
    void insertUser(User user);
    void updateUser(User user);
    void deleteUser(int id);
}

UserDao.xml（resources/mapper/UserDao.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.example.dao.UserDao">
    <select id="getUserById" resultMap="userResultMap">
        select * from users where id = #{id}
    </select>
    <select id="getUsers" resultMap="userResultMap">
        select * from users
    </select>
    <insert id="insertUser">
        insert into users (username, password, email) values (#{username}, #{password}, #{email})
    </insert>
    <update id="updateUser">
        update users set username = #{username}, password = #{password}, email = #{email} where id = #{id}
    </update>
    <delete id="deleteUser">
        delete from users where id = #{id}
    </delete>
    <resultMap id="userResultMap" type="com.example.entity.User">
        <id property="id" column="id"/>
        <result property="username" column="username"/>
        <result property="password" column="password"/>
        <result property="email" column="email"/>
    </resultMap>
</mapper>

6. 创建 MyBatis 配置文件（resources/mybatis-config.xml）

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis_demo?useSSL=false&serverTimezone=UTC"/>
                <property name="username" value="root"/>
                <property name="password" value="your_password"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="mapper/UserDao.xml"/>
    </mappers>
</configuration>

7. 创建工具类（com.example.util.MyBatisUtil）用于获取 SqlSessionFactory

package com.example.util;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import java.io.IOException;
import java.io.InputStream;

public class MyBatisUtil {
    private static SqlSessionFactory sqlSessionFactory;

    static {
        try {
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static SqlSessionFactory getSqlSessionFactory() {
        return sqlSessionFactory;
    }
}

8. 创建服务层（Service）接口和实现类

UserService 接口（com.example.service.UserService）

package com.example.service;

import com.example.entity.User;
import java.util.List;

public interface UserService {
    User getUserById(int id);
    List<User> getUsers();
    void insertUser(User user);
    void updateUser(User user);
    void deleteUser(int id);
}

UserServiceImpl 实现类（com.example.service.impl.UserServiceImpl）

package com.example.service.impl;

import com.example.dao.UserDao;
import com.example.entity.User;
import com.example.service.UserService;
import com.example.util.MyBatisUtil;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import java.util.List;

public class UserServiceImpl implements UserService {

    private SqlSessionFactory sqlSessionFactory = MyBatisUtil.getSqlSessionFactory();

    @Override
    public User getUserById(int id) {
        try (SqlSession sqlSession = sqlSessionFactory.openSession()) {
            UserDao userDao = sqlSession.getMapper(UserDao.class);
            return userDao.getUserById(id);
        }
    }

    @Override
    public List<User> getUsers() {
        try (SqlSession sqlSession = sqlSessionFactory.openSession()) {
            UserDao userDao = sqlSession.getMapper(UserDao.class);
            return userDao.getUsers();
        }
    }

    @Override
    public void insertUser(User user) {
        try (SqlSession sqlSession = sqlSessionFactory.openSession()) {
            UserDao userDao = sqlSession.getMapper(UserDao.class);
            userDao.insertUser(user);
            sqlSession.commit();
        }
    }

    @Override
    public void updateUser(User user) {
        try (SqlSession sqlSession = sqlSessionFactory.openSession()) {
            UserDao userDao = sqlSession.getMapper(UserDao.class);
            userDao.updateUser(user);
            sqlSession.commit();
        }
    }

    @Override
    public void deleteUser(int id) {
        try (SqlSession sqlSession = sqlSessionFactory.openSession()) {
            UserDao userDao = sqlSession.getMapper(UserDao.class);
            userDao.deleteUser(id);
            sqlSession.commit();
        }
    }
}

9. 测试类（可以在 main 方法中进行简单测试）

import com.example.entity.User;
import com.example.service.UserService;
import com.example.service.impl.UserServiceImpl;
import java.util.List;

public class Main {
    public static void main(String[] args) {
        UserService userService = new UserServiceImpl();

        // 插入用户
        User newUser = new User();
        newUser.setUsername("testuser");
        newUser.setPassword("testpassword");
        newUser.setEmail("test@example.com");
        userService.insertUser(newUser);

        // 查询用户
        List<User> users = userService.getUsers();
        for (User user : users) {
            System.out.println(user);
        }

        // 根据 ID 查询用户
        User userById = userService.getUserById(1);
        System.out.println(userById);

        // 更新用户
        User updateUser = new User();
        updateUser.setId(1);
        updateUser.setUsername("updateduser");
        updateUser.setPassword("updatedpassword");
        updateUser.setEmail("updated@example.com");
        userService.updateUser(updateUser);

        // 删除用户
        userService.deleteUser(1);
    }
}

这个案例详细展示了如何使用 MyBatis 进行数据库操作，包括从项目搭建、配置文件编写、实体类和接口创建，到数据库的增删改查操作的实现。你可以根据实际需求进一步扩展和优化这个案例。