spring-boot - Spring Data JPA @Query - 选择最大值

Question

我正在尝试使用 select max&where 和 @Query 编写查询

以下内容不起作用，我该如何解决？

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.Query
import org.springframework.data.repository.query.Param;
import org.springframework.stereotype.Repository;

@Repository
interface IntermediateInvoiceRepository extends JpaRepository<Invoice, String> {

@Query("SELECT max(i.sequence) " +
        "FROM Invoice as i " +
        "WHERE i.fleetId = :fleetId" +
        "   AND i.sequence IS NOT NULL")
Long findMaxSequence(@Param("fleetId") String fleetId);

}

我遇到了另一个答案，但它明确地使用了实体管理器，操作系统不一样

How do I write a MAX query with a where clause in JPA 2.0?

错误是:

2018-09-14T09:27:57,180Z  [main] ERROR o.s.boot.SpringApplication     - Application startup failed
org.springframework.data.mapping.PropertyReferenceException: No property findMaxSequence found for type Invoice!

发票类别(为简洁起见进行了简化):

@Entity
@Cache(usage = CacheConcurrencyStrategy.NONSTRICT_READ_WRITE)
@Table(name = "invoices", indexes = {
        @Index(name = "IDX_FLEET", columnList = "fleetId", unique = false)
        ,
        @Index(name = "IDX_USERSSS", columnList = "userId", unique = false)
        ,
        @Index(name = "IDX_TIME", columnList = "invoiceDate", unique = false)
        ,
        @Index(name = "IDX_SEQUENCE", columnList = "sequence", unique = false)
})
@JsonIgnoreProperties(ignoreUnknown = true)
public class Invoice implements Serializable {

    private static final long serialVersionUID = 1L;

    @GeneratedValue(generator = "uuid")
    @GenericGenerator(name = "uuid", strategy = "uuid2")
    @Column(columnDefinition = "CHAR(36)")
    @Id
    private String id;

    @Column
    private long sequence;

...

更新:

• 也许可以使用 findOne 对序列进行 DESC 排序专栏？

  @Query("SELECT i.sequence "+ “作为我的发票” + “哪里 i.fleetId = :fleetId” + “按 i.sequence DESC 排序”) Long getMaxSequence(@Param("fleetId") String fleetId);

但我需要以某种方式将结果集限制为 1

更新 2:

修复了 import org.springframework.data.jpa.repository.Query; 仍然出错

Answer 1

由于您使用的是 JPA 存储库，因此请使用:

org.springframework.data.jpa.repository.Query

注解代替

org.springframework.data.mongodb.repository.Query

您可以创建一个查询方法，而不使用@Query 注释，例如:

发票 findFirstByFleetIdOrderBySequenceDesc(String fleetId);

返回您需要的发票。