SpringBoot配置mybatis-plus

下面是SpringBoot配置MyBatis-Plus的详细步骤：

1. 添加依赖

<dependencies>
    <!-- SpringBoot -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    
    <!-- MyBatis-Plus -->
    <dependency>
        <groupId>com.baomidou</groupId>
        <artifactId>mybatis-plus-boot-starter</artifactId>
        <version>3.5.3.1</version>
    </dependency>
    
    <!-- MySQL驱动 -->
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>8.0.28</version>
    </dependency>
    
    <!-- Lombok -->
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <optional>true</optional>
    </dependency>
</dependencies>

2. 配置文件

application.yml:

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

mybatis-plus:
  # mapper.xml文件位置
  mapper-locations: classpath:mapper/*.xml
  # 实体类包路径
  type-aliases-package: com.example.entity
  configuration:
    # 驼峰命名转换
    map-underscore-to-camel-case: true
    # 打印SQL语句（开发环境使用）
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl
  global-config:
    db-config:
      # 主键生成策略
      id-type: auto
      # 逻辑删除配置
      logic-delete-field: deleted
      logic-delete-value: 1
      logic-not-delete-value: 0

3. 实体类

@Data
@TableName("user")
public class User {
    // 主键
    @TableId(type = IdType.AUTO)
    private Long id;
    
    // 普通字段
    private String username;
    private String password;
    
    // 逻辑删除
    @TableLogic
    private Integer deleted;
    
    // 乐观锁
    @Version
    private Integer version;
    
    // 自动填充
    @TableField(fill = FieldFill.INSERT)
    private LocalDateTime createTime;
    
    @TableField(fill = FieldFill.INSERT_UPDATE)
    private LocalDateTime updateTime;
}

4. Mapper接口

@Mapper
public interface UserMapper extends BaseMapper<User> {
    // 继承BaseMapper后即可使用内置的CRUD方法
    
    // 自定义方法
    @Select("SELECT * FROM user WHERE username = #{username}")
    User findByUsername(String username);
}

5. Service层

// 接口
public interface UserService extends IService<User> {
    User findByUsername(String username);
}

// 实现类
@Service
public class UserServiceImpl extends ServiceImpl<UserMapper, User> implements UserService {
    
    @Autowired
    private UserMapper userMapper;
    
    @Override
    public User findByUsername(String username) {
        return userMapper.findByUsername(username);
    }
}

6. 配置类

@Configuration
@MapperScan("com.example.mapper")
public class MybatisPlusConfig {
    
    /**
     * 分页插件
     */
    @Bean
    public MybatisPlusInterceptor mybatisPlusInterceptor() {
        MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
        // 分页插件
        interceptor.addInnerInterceptor(new PaginationInnerInterceptor(DbType.MYSQL));
        // 乐观锁插件
        interceptor.addInnerInterceptor(new OptimisticLockerInnerInterceptor());
        return interceptor;
    }
    
    /**
     * 自动填充处理器
     */
    @Bean
    public MetaObjectHandler metaObjectHandler() {
        return new MetaObjectHandler() {
            @Override
            public void insertFill(MetaObject metaObject) {
                this.strictInsertFill(metaObject, "createTime", LocalDateTime.class, LocalDateTime.now());
                this.strictInsertFill(metaObject, "updateTime", LocalDateTime.class, LocalDateTime.now());
            }
            
            @Override
            public void updateFill(MetaObject metaObject) {
                this.strictUpdateFill(metaObject, "updateTime", LocalDateTime.class, LocalDateTime.now());
            }
        };
    }
}

7. Controller层

@RestController
@RequestMapping("/api/users")
public class UserController {
    
    @Autowired
    private UserService userService;
    
    // 分页查询
    @GetMapping
    public IPage<User> list(@RequestParam(defaultValue = "1") Integer page,
                           @RequestParam(defaultValue = "10") Integer size) {
        return userService.page(new Page<>(page, size));
    }
    
    // 条件查询
    @GetMapping("/search")
    public List<User> search(String username) {
        return userService.list(new QueryWrapper<User>()
                .like("username", username));
    }
    
    // 添加
    @PostMapping
    public boolean save(@RequestBody User user) {
        return userService.save(user);
    }
    
    // 修改
    @PutMapping
    public boolean update(@RequestBody User user) {
        return userService.updateById(user);
    }
    
    // 删除
    @DeleteMapping("/{id}")
    public boolean delete(@PathVariable Long id) {
        return userService.removeById(id);
    }
}

8. XML映射文件

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.mapper.UserMapper">
    
    <!-- 自定义复杂查询 -->
    <select id="getComplexData" resultType="com.example.vo.UserVO">
        SELECT 
            u.id,
            u.username,
            r.role_name
        FROM user u
        LEFT JOIN user_role ur ON u.id = ur.user_id
        LEFT JOIN role r ON ur.role_id = r.id
        WHERE u.deleted = 0
    </select>
    
</mapper>

9. 常用操作示例

@Service
public class UserServiceImpl extends ServiceImpl<UserMapper, User> implements UserService {
    
    // 条件构造器示例
    public List<User> searchUsers(String keyword) {
        return list(new QueryWrapper<User>()
            .like("username", keyword)
            .or()
            .like("email", keyword)
            .orderByDesc("create_time"));
    }
    
    // 分页查询示例
    public IPage<User> pageUsers(int page, int size) {
        return page(new Page<>(page, size), new QueryWrapper<User>()
            .orderByDesc("create_time"));
    }
    
    // 批量操作示例
    public boolean batchSave(List<User> users) {
        return saveBatch(users);
    }
    
    // 链式调用示例
    public User getOneUser(String username) {
        return lambdaQuery()
            .eq(User::getUsername, username)
            .one();
    }
}

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