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

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。