Mybatis-Plus 真好用

数据库准备

CREATE TABLE tbl_user(	user_id BIGINT(20) NOT NULL COMMENT '主键ID',	user_name VARCHAR(30) NULL DEFAULT NULL COMMENT '姓名',	user_age INT(11) NULL DEFAULT NULL COMMENT '年龄',	PRIMARY KEY (user_id)) charset = utf8;

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MyBatis-Plus加持

• 工程搭建 （不赘述了）
• 依赖引入

<dependency>
	<groupId>com.baomidou</groupId>
	<artifactId>mybatis-plus-boot-starter</artifactId>
	<version>3.1.0</version>
</dependency>

<dependency>
	<groupId>org.projectlombok</groupId>
	<artifactId>lombok</artifactId>
</dependency>

<dependency>
	<groupId>com.alibaba</groupId>
	<artifactId>druid-spring-boot-starter</artifactId>
	<version>1.1.9</version>
</dependency>

<dependency>
	<groupId>mysql</groupId>
	<artifactId>mysql-connector-java</artifactId>
	<scope>runtime</scope>
	<version>8.0.12</version>
</dependency>

主要是 Mybatis Plus、Lombok（不知道Lombok干嘛的？可以看这里）、Druid连接池 等依赖。

MyBatis Plus配置

项目配置

mybatis-plus:
  mapper-locations: classpath:/mapper/*Mapper.xml

新增 MyBatis Plus配置类

@Configuration
@MapperScan("cn.codesheep.springbtmybatisplus.mapper")
public class MyBatisConfig {
}

看到没，几乎零配置啊，下面就可以写业务逻辑了

业务编写

• 实体类

@Data
@TableName("tbl_user")
public class User {
    @TableId(value = "user_id")
    private Long userId;
    private String userName;
    private Integer userAge;
}

• Mapper类

public interface UserMapper extends BaseMapper<User> {}

这里啥接口方法也不用写，就可以实现增删改查了！

• Service类

Service接口：

public interface UserService extends IService<User> {
    int insertUser( User user );
    int updateUser( User user );
    int deleteUser( User user );
    User findUserByName( String userName );
    IPage getUserPage( Page page, User user );
}

Service实现：

@Service
@AllArgsConstructor
public class UserServiceImpl extends ServiceImpl<UserMapper, User> implements UserService {

    // 增
    @Override
    public int insertUser(User user) {
        return baseMapper.insert( user );
    }

    // 改
    @Override
    public int updateUser(User user) {
        return baseMapper.updateById( user );
    }

    // 删
    @Override
    public int deleteUser(User user) {
        return baseMapper.deleteById( user.getUserId() );
    }

    // 查
    @Override
    public User findUserByName( String userName ) {
        return baseMapper.getUserByName( userName );
    }
}

• Controller类

@RestController
@RequestMapping("/user")
public class UserContorller {

    @Autowired
    private UserService userService;

    // 增
    @PostMapping( value = "/insert")
    public Object insert( @RequestBody User user ) {
        return userService.insertUser( user );
    }

    // 改
    @PostMapping( value = "/update")
    public Object update( @RequestBody User user ) {
        return userService.updateUser( user );
    }

    // 删
    @PostMapping( value = "/delete")
    public Object delete( @RequestBody User user ) {
        return userService.deleteUser( user );
    }

    // 查
    @GetMapping( value = "/getUserByName")
    public Object getUserByName( @RequestParam String userName ) {
        return userService.findUserByName( userName );
    }
}

通过以上几个简单的步骤，我们就实现了 tbl_user表的增删改查，传统 MyBatis的 XML文件一个都不需要写！

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最关心的分页问题

• 首先装配分页插件

@Bean
public PaginationInterceptor paginationInterceptor() {
	return new PaginationInterceptor();
}

• Mapper类

public interface UserMapper extends BaseMapper<User> {

    // 普通查询
    User getUserByName( String userName );

    // 分页查询
    IPage<List<User>> getUsersPage( Page page, @Param("query") User user );
}

• Service类

@Service
@AllArgsConstructor
public class UserServiceImpl extends ServiceImpl<UserMapper, User> implements UserService {

    // 查：普通查
    @Override
    public User findUserByName( String userName ) {
        return baseMapper.getUserByName( userName );
    }

    // 分页查
    @Override
    public IPage getUserPage(Page page, User user) {
        return baseMapper.getUsersPage( page, user );
    }
}

• Controller类

@GetMapping( value = "/page")
public Object getUserPage( Page page, User user ) {
	return userService.getUserPage( page, user );
}