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编程网。
