Spring|Spring Data JPA 映射VO/DTO对象方式 SpringDataJPA映射VO

Spring Data JPA 映射VO/DTO对象

HQL方式
原生SQL的形式

Spring Data Jpa 自定义repository转DTO

Spring Data JPA 映射VO/DTO对象在项目开发中,时常需要根据业务需求来映射VO/DTO对象(这两个概念理解感觉很模糊- 。- )，本文将简单介绍以Spring Data JPA的方式处理实体类映射

HQL方式

public interface MusicTypeRepository extends JpaRepository {@Query("select new cn.srblog.springbootcurd.vo.StudentTypeInfoVo(count(s.id),m.name) " +"FROM MusicType mleft JOIN Student s on s.musicTypeId = m.id group by m.id ")List getTypeInfo(); }

填写实体类路径,构造参数顺序要一致,字段名一律为实体类中的属性
如果配置了实体类属性的映射关系，则on s.musicTypeId = m.id语句可以省略

VO实体类

@Valuepublic class StudentTypeInfoVo{private Long count; private String name; }

使用Lombok的 @Value 注解

默认生成带参构造方法
默认为成员变量添加final修饰,且只提供getter()方法

原生SQL的形式
接口形式

public interface CoursePlanRepository extends JpaRepository {@Query(nativeQuery = true,value = "https://www.it610.com/article/SELECT" +" c.id as id," +"DAYOFWEEK(c.start_time) as week," +"m.name as musicType," +"t.name as teacherName," +"c.start_time as startTime," +"c.end_time as endTime " +" FROM t_courseplan c,t_musictype m , t_teacher t " +" WHERE DATE(c.start_time) < DATE_ADD(CURDATE(), INTERVAL 7 DAY ) AND CURDATE() <= DATE(c.start_time) " +" and t.id=c.tea_id and c.music_type_id = m.id order by c.start_time ")List getWeekList(); }

nativeQuery = true 表示开启原生SQL查询
查询字段别名需要与实体类中字段一一对应
该方法功能为查询一周后的数据

函数	说明
DAYOFWEEK()	DAYOFWEEK函数返回日期的工作日索引值，即星期日为1，星期一为2，星期六为7。例:DAYOFWEEK('2019-05-09') 返回 5
DATE()	提取日期或日期/时间表达式的日期部分,格式'YYYY-MM-DD'或者'YYYYMMDD'
DATE_ADD(date,INTERVAL expr unit)	给日期添加指定的时间间隔。date 参数是合法的日期表达式,expr 参数是您希望添加的时间间隔,type 参数可以是MySQL支持的时间日期相关类型值
CURDATE()	返回当前日期例:'2019-05-09'

VO实体类(接口形式)

public interface CoursePlanVos{Integer getId(); Integer getWeek(); String getMusicType(); String getTeacherName(); Date getStartTime() ; Date getEndTime(); }

结果集形式

@Query(value = "https://www.it610.com/article/select count(s.id) as count,m.name as name" +" FROM t_musictype mleft JOIN t_student s on s.music_type_id = m.id group by m.id ",nativeQuery = true)List listType1();

对比第一种方法,使用原生SQL默认会返回Object数组
【Spring|Spring Data JPA 映射VO/DTO对象方式】
Spring Data Jpa 自定义repository转DTO 近期项目中需要关联几张表再把字段转出来，在这里记录以下，我感觉网上写的都不太规范和清晰。

@Entity@SqlResultSetMapping(name="TestMapping",entities = {@EntityResult(entityClass = com.xxx.xx.data.model.TestEntity.class,fields = {@FieldResult(name="id",column="id"),@FieldResult(name="localTime",column="time"),@FieldResult(name="maximumAppointment",column="maxAppointment"),})})@NamedNativeQuery(name="getTestQuery",query="select tableC.id as id,tableB.time,tableC.maximumAppointment as maxAppointment from tableB " +"inner join tableA on tableA.id = tableB.tableAId " +"inner join tableC on tableB.id = tableC.tableBId " +"inner join custom on custom.id = tableA.customId " +"where " +"tableA.locationId = :locationId" +"and custom.id = :customId" +"and tableB.deleted = false ", resultSetMapping="TestMapping")@Datapublic class TestEntity {@Idprivate String id; private LocalTime localTime; private Integer maximumAppointment; }

需要声明接口：

@Repositorypublic interface TestEntityRepository extends JpaRepository {@Query(name="getTestQuery")List getTestQuery(String locationId, String customId); }

若不想声明接口，那可以用EntityManager 来实现。