Spring Data JPA 映射VO/DTO对象方式

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czfacssDTO

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 m left 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

@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 {

@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_typeczfaCSs_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 = "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

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 {

@Query(name="getTestQuery")

List getTestQuery(String locationId, String customId);

}

若不想声明接口，那可以用EntityManager 来实现。

CriteriaBuilder criteriaBuilder = entityManager.getCriteriaBuilder();

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