Spring boot + Mybatis 实现数据库的增删改查（CRUD）操作

在Spring Boot项目中使用MyBatis实现CRUD操作，首先需要添加相关依赖，配置数据源和MyBatis，然后定义Mapper接口和对应的XML映射文件。

1. 添加依赖到pom.xml：

<dependencies>
    <!-- Spring Boot相关依赖 -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <!-- MyBatis依赖 -->
    <dependency>
        <groupId>org.mybatis.spring.boot</groupId>
        <artifactId>mybatis-spring-boot-starter</artifactId>
        <version>2.1.4</version>
    </dependency>
    <!-- 数据库驱动，例如MySQL -->
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <scope>runtime</scope>
    </dependency>
</dependencies>

2. 配置application.properties或application.yml：

spring.datasource.url=jdbc:mysql://localhost:3306/your_database?useSSL=false&serverTimezone=UTC
spring.datasource.username=root
spring.datasource.password=yourpassword
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
mybatis.mapper-locations=classpath:mapper/*.xml

3. 创建Mapper接口：

package com.example.demo.mapper;
 
public interface UserMapper {
    User selectUserById(int id);
    int insertUser(User user);
    int updateUser(User user);
    int deleteUserById(int id);
}

4. 创建Mapper XML映射文件：

<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.example.demo.mapper.UserMapper">
    <select id="selectUserById" resultType="com.example.demo.model.User">
        SELECT * FROM users WHERE id = #{id}
    </select>
    <insert id="insertUser" parameterType="com.example.demo.model.User">
        INSERT INTO users(name, email) VALUES(#{name}, #{email})
    </insert>
    <update id="updateUser" parameterType="com.example.demo.model.User">
        UPDATE users SET name = #{name}, email = #{email} WHERE id = #{id}
    </update>
    <delete id="deleteUserById">
        DELETE FROM users WHERE id = #{id}
    </delete>
</mapper>

5. 创建Service层：

package com.example.demo.service;
 
@Service
public class UserService {
    @Autowired
    private UserMapper userMapper;
 
    public User getUserById(int id) {
        return userMapper.selectUserById(id);
    }
 
    public int createUser(User user) {
        return userMapper.i