Spring Data JPA 映射VO/DTO对象方式
目录
- 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<MusicType,Integer> { @Query("select new cn.srblog.springbootcurd.vo.StudentTypeInfoVo(count(s.id),m.name) " + "FROM MusicType m left JOIN Student s on s.musicTypeId = m.id group by m.id ") List<StudentTypeInfoVo> 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
@Value public 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<CoursePlan,Integer> { @Query(nativeQuery = true,value = "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<CoursePlanVos> 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 = "select count(s.id) as count,m.name as name " + " FROM t_musictype m left JOIN t_student s on s.music_type_id = m.id group by m.id ",nativeQuery = true) List<Object[]> listType1();
对比第一种方法,使用原生SQL默认会返回Object数组
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") @Data public class TestEntity { @Id private String id; private LocalTime localTime; private Integer maximumAppointment; }
需要声明接口:
@Repository public interface TestEntityRepository extends JpaRepository<TestEntity,String> { @Query(name="getTestQuery") List<TestEntity> getTestQuery(String locationId, String customId); }
若不想声明接口,那可以用EntityManager 来实现。
CriteriaBuilder criteriaBuilder = entityManager.getCriteriaBuilder();
以上为个人经验,希望能给大家一个参考,也希望大家多多支持我们。
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