mybatisPlus基本用法

1.pom.xml

<!--    mybatisPlus-->
<dependency>
  <groupId>com.baomidou</groupId>
  <artifactId>mybatis-plus-boot-starter</artifactId>
  <version>2.3</version>
</dependency>

2.配置文件

3.实体类

@Data
@TableName("student")
public class Student {
    @TableId(value = "sid", type = IdType.AUTO)
    private Integer sid;

    @TableField("name")
    private String name;
    
    private Integer age;
}

4.mapper

public interface StudentMapper extends BaseMapper<Student> {
}

4.1 常用方法

• int insert(T entity);
• int deleteById(Serializable id);
• int updateById(@Param(Constants.ENTITY) T entity);
• T selectById(Serializable id);

5.service

public interface StudentService extends IService<Student> {
}

5.1 常用方法

• boolean save(T entity);
• boolean removeById(Serializable id);
• boolean update(Wrapper updateWrapper);
• T getById(Serializable id);
• List list(Wrapper queryWrapper);

6.分页

4.测试类

@SpringBootTest
@RunWith(SpringRunner.class)
public class TestStudent {
    @Resource
    private StudentMapper studentMapper;

    @Test
    public void test(){
        List<Student> list = studentMapper.selectList(null);
        list.forEach(System.out::println);
    }
}

5.条件构造器

5.1 LambdaQueryWrapper

基于 Lambda 表达式的查询条件构造器，它通过 Lambda 表达式来引用实体类的属性，从而避免了硬编码字段名

• 带聚合函数

 LambdaQueryWrapper<TSaleAutosaleorderPo> queryWrapper = new QueryWrapper<TSaleAutosaleorderPo>()
                .select("pay_type", "count(*) as count")
                .lambda()
                .ne(TSaleAutosaleorderPo::getStatus, AutoSaleOrderStatusEnum.CANCELED.getKey())

• 基本使用

LambdaQueryWrapper<TSaleAutosaleorderPo> queryWrapper = new LambdaQueryWrapper<TSaleAutosaleorderPo>()
                .ne(TSaleAutosaleorderPo::getStatus, AutoSaleOrderStatusEnum.CANCELED.getKey())
                .eq(TSaleAutosaleorderPo::getAssignVehicleStatus, AssignVehicleStatusEnum.WPC.getKey())
                .select(TSaleAutosaleorderPo::getId)

• 比较相关

gt(User::getAge, 18) >18
ge(User::getAge, 18) >=18
lt(User::getAge, 18) <18
le(User::getAge, 18) <=18
between(User::getAge, 18, 30) BETWEEN 18 AND 30

5.2 LambdaUpdateWrapper