Spring Boot整合MyBatis

Spring Boot + MyBatis 是 Java 后端开发中最常见的技术组合之一。本文记录完整的整合过程和 CRUD 实现。

添加依赖

pom.xml：

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <dependency>
        <groupId>org.mybatis.spring.boot</groupId>
        <artifactId>mybatis-spring-boot-starter</artifactId>
        <version>2.2.0</version>
    </dependency>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <scope>runtime</scope>
    </dependency>
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <optional>true</optional>
    </dependency>
</dependencies>

数据源配置

application.yml：

spring:
  datasource:
    url: jdbc:mysql://localhost:3306/demo?useSSL=false&serverTimezone=Asia/Shanghai&characterEncoding=utf8
    username: root
    password: root123
    driver-class-name: com.mysql.cj.jdbc.Driver

mybatis:
  mapper-locations: classpath:mapper/*.xml
  type-aliases-package: com.example.demo.entity
  configuration:
    map-underscore-to-camel-case: true
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl

map-underscore-to-camel-case: true 自动把数据库的 user_name 映射到 Java 的 userName。

建表

CREATE TABLE `user` (
  `id` bigint NOT NULL AUTO_INCREMENT,
  `username` varchar(50) NOT NULL,
  `email` varchar(100) DEFAULT NULL,
  `age` int DEFAULT NULL,
  `create_time` datetime DEFAULT CURRENT_TIMESTAMP,
  `update_time` datetime DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
  PRIMARY KEY (`id`),
  UNIQUE KEY `uk_username` (`username`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;

实体类

package com.example.demo.entity;

import lombok.Data;
import java.time.LocalDateTime;

@Data
public class User {
    private Long id;
    private String username;
    private String email;
    private Integer age;
    private LocalDateTime createTime;
    private LocalDateTime updateTime;
}

Mapper 接口

package com.example.demo.mapper;

import com.example.demo.entity.User;
import org.apache.ibatis.annotations.*;
import java.util.List;

public interface UserMapper {

    // 注解方式 —— 简单 SQL 直接写注解
    @Select("SELECT * FROM user WHERE id = #{id}")
    User findById(Long id);

    @Insert("INSERT INTO user(username, email, age) VALUES(#{username}, #{email}, #{age})")
    @Options(useGeneratedKeys = true, keyProperty = "id")
    int insert(User user);

    @Delete("DELETE FROM user WHERE id = #{id}")
    int deleteById(Long id);

    // XML 方式 —— 复杂 SQL 写在 XML 里
    List<User> findByCondition(@Param("username") String username,
                                @Param("minAge") Integer minAge);

    int updateSelective(User user);
}

Mapper XML

resources/mapper/UserMapper.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.demo.mapper.UserMapper">

    <select id="findByCondition" resultType="User">
        SELECT * FROM user
        <where>
            <if test="username != null and username != ''">
                AND username LIKE CONCAT('%', #{username}, '%')
            </if>
            <if test="minAge != null">
                AND age >= #{minAge}
            </if>
        </where>
        ORDER BY create_time DESC
    </select>

    <update id="updateSelective">
        UPDATE user
        <set>
            <if test="username != null">username = #{username},</if>
            <if test="email != null">email = #{email},</if>
            <if test="age != null">age = #{age},</if>
        </set>
        WHERE id = #{id}
    </update>

</mapper>

<where> 标签会自动处理多余的 AND/OR，<set> 标签会自动处理多余的逗号。

启动类配置

package com.example.demo;

import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
@MapperScan("com.example.demo.mapper")
public class DemoApplication {
    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }
}

@MapperScan 扫描指定包下的所有 Mapper 接口，自动生成代理实现并注册到 Spring 容器。也可以在每个 Mapper 接口上加 @Mapper 注解代替。

Service 层

package com.example.demo.service;

import com.example.demo.entity.User;
import com.example.demo.mapper.UserMapper;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import java.util.List;

@Service
public class UserService {

    private final UserMapper userMapper;

    public UserService(UserMapper userMapper) {
        this.userMapper = userMapper;
    }

    public User getById(Long id) {
        return userMapper.findById(id);
    }

    @Transactional
    public User create(User user) {
        userMapper.insert(user);
        return user; // id 已通过 useGeneratedKeys 回填
    }

    @Transactional
    public int update(User user) {
        return userMapper.updateSelective(user);
    }

    public List<User> search(String username, Integer minAge) {
        return userMapper.findByCondition(username, minAge);
    }

    @Transactional
    public int delete(Long id) {
        return userMapper.deleteById(id);
    }
}

Controller 层

package com.example.demo.controller;

import com.example.demo.entity.User;
import com.example.demo.service.UserService;
import org.springframework.web.bind.annotation.*;

import java.util.List;

@RestController
@RequestMapping("/api/users")
public class UserController {

    private final UserService userService;

    public UserController(UserService userService) {
        this.userService = userService;
    }

    @GetMapping("/{id}")
    public User getById(@PathVariable Long id) {
        return userService.getById(id);
    }

    @PostMapping
    public User create(@RequestBody User user) {
        return userService.create(user);
    }

    @PutMapping("/{id}")
    public int update(@PathVariable Long id, @RequestBody User user) {
        user.setId(id);
        return userService.update(user);
    }

    @GetMapping
    public List<User> search(@RequestParam(required = false) String username,
                              @RequestParam(required = false) Integer minAge) {
        return userService.search(username, minAge);
    }

    @DeleteMapping("/{id}")
    public int delete(@PathVariable Long id) {
        return userService.delete(id);
    }
}

小结

整合过程：加依赖 → 配数据源 → 写实体类 → 写 Mapper 接口(+XML) → @MapperScan → 正常写 Service/Controller。简单 SQL 用注解，复杂动态 SQL 用 XML，两种方式可以混用。生产项目建议配合 PageHelper 做分页，配合 MyBatis-Plus 减少模板代码。