配置

• pom配置

<dependency>
    <groupId>com.baomidou</groupId>
    <artifactId>mybatis-plus-boot-starter</artifactId>
    <version>3.3.1.tmp</version>
</dependency>

• MapperScan配置
  在主类上添加@MapperScan("com.mapper")注释

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

• 项目配置

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

实体类

• User.java

@Data
@TableName("p_user")
public class User {
    @TableId(type = IdType.AUTO, value = "u_id")
    private Long id;
    private String userName;
    private String password;
    private Integer age;
}

Mapper接口

public interface UserMapper extends BaseMapper<User> {
}

controller

• 注入mapper

    @Autowired
    UserMapper mapper;

• 增
  mapper.insert(user)

    //增
    @RequestMapping("/insertUser")
    public Integer insertUser(User user) {
        return mapper.insert(user);
    }

• 删
  mapper.delete(queryWrapper)

    //删
    @RequestMapping("/deleteUserByAge")
    public Integer delete(Integer age) {
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper
                .eq("age", age);
        int delete = mapper.delete(queryWrapper);//删除的数量
        System.out.println("delete return count = " + delete);
        return delete;
    }

• 改
  mapper.update(user, userUpdateWrapper)

    //改
    @RequestMapping("/updateUser")
    public Integer update(String userName, String psw) {
        User user = new User();
        user.setPassword(psw);

        UpdateWrapper<User> userUpdateWrapper = new UpdateWrapper<>();
        userUpdateWrapper
                .eq("user_name", userName);

        Integer update = mapper.update(user, userUpdateWrapper);

        return update;
    }

• 查

  • selectOne
    name是唯一的，所以使用selectOne

  //查
  @RequestMapping("/getUserByName")
  public User getUserByName(String userName) {
      QueryWrapper<User> queryWrapper = new QueryWrapper<>();
      queryWrapper
              .eq("user_name", userName);
  
      User user = mapper.selectOne(queryWrapper);
      return user;
  }
  

  • selectList
    age不唯一，所以使用selectList

  @RequestMapping("/getUserByAge")
  public List<User> getUserByAge(Integer age) {
      QueryWrapper<User> queryWrapper = new QueryWrapper<>();
      queryWrapper
              .eq("age", age);
  
      List<User> users = mapper.selectList(queryWrapper);
      return users;
  }
  

  • selectCount
    查询数目

  @RequestMapping("/getCountByAge")
  public Integer getCountByAge(Integer age) {
      QueryWrapper<User> queryWrapper = new QueryWrapper<>();
      queryWrapper
              .eq("age", age);
  
      Integer count = mapper.selectCount(queryWrapper);
      return count;
  }
  

  • selectMaps

  @RequestMapping("/getMaps")
  public List<Map<String, Object>> selectMaps() {
      QueryWrapper<User> queryWrapper = new QueryWrapper<>();
  
      List<Map<String, Object>> maps = mapper.selectMaps(queryWrapper);
      return maps;
  }
  

  • selectPage
    查询第几页(5条一页)

  @RequestMapping("/getPage")
  public List<User> selectPage(Integer page) {
      Page<User> p = new Page<>(page, 5);
      QueryWrapper<User> queryWrapper = new QueryWrapper<>();
  
      IPage<User> userIPage = mapper.selectPage(p, queryWrapper);
      return userIPage.getRecords();//返回List<User>
  }
  

QueryWrapper参考