JPA Join Query(本地查询)自定义dto [英] JPA Join Query(native query) custom dto

问题描述

我正在尝试加入3个表并使用以下查询获取集体结果，即dto

Hi I am trying to join 3 table and fetch the collective result i.e dto using following query

SELECT f.id, u.email,
count(distinct l.id) as likes_count,
count(distinct c.id) as comments_count
FROM feeds f 
INNER JOIN users u ON f.user_id = u.id
INNER JOIN likes l on l.feed_id = f.id 
left join comments c on c.feed_id = f.id
WHERE u.id = 12055
group by f.id order by comments_count asc;

此查询在mysql工作台中工作正常，当我尝试将此查询添加到@Query批注中时，我遇到了AbstractJpaQuery$TupleConverter$TupleBackedMap异常，对此的解决方法是使用ContructorExpression我添加了new表达式，但我无法正常工作，我的数据库实体如下所示:

This query is working fine in mysql workbench, when i try to add this query to @Query annotation i am geeting AbstractJpaQuery$TupleConverter$TupleBackedMap exception, solution to this was to use ContructorExpression i added new expression but i am not getting it worked, my db entities are as below

@Entity
@Table(name = "feeds")
@NoArgsConstructor
public class Feed {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Getter
    @Setter
    Long id;

    @Getter
    @Setter
    @Column(columnDefinition = "TEXT")
    String content;

    public Feed(String content, User user) {
        this.content = content;
        this.user = user;
    }

    @ManyToOne(optional = false, cascade = CascadeType.ALL, fetch = FetchType.LAZY)
    @Getter
    @Setter
    User user;


    @OneToMany(mappedBy = "feed", fetch = FetchType.LAZY, cascade = CascadeType.ALL, orphanRemoval = true)
    @Getter
    @Setter
    List<Like> likes;


    @OneToMany(mappedBy = "feed", fetch = FetchType.LAZY, cascade = CascadeType.ALL, orphanRemoval = true)
    @Getter
    @Setter
    List<Comment> comments;

    @Override
    public String toString() {
        return "Feed{" +
                "id=" + id +
                ", user=" + user +
                '}';
    }
}

上述SQL查询的自定义DTO对象:

Custom DTO Object for above sql query:

@NoArgsConstructor
@AllArgsConstructor
public class FeedDetails {

    @Getter
    @Setter
    private Long id;


    @Getter
    @Setter
    private Long likes;

    @Getter
    @Setter
    private Long comments;


}

Repository方法如下:

@Query("**sql_query**")
List<FeedDetails> findAllFeedsByUserId(Long userId);

我不确定我在sql_query中写了什么叫什么，以便得到正确的FeedDetails List结果.

I am not sure what shout i write in sql_query such that i get proper FeedDetails List result.

推荐答案

您不能对本机查询使用构造函数表达式(NEW运算符).

You cannot use constructor expression (NEW operator) with Native Queries.

您可以使用JPA构造函数结果.看起来像:

You could use JPA constructor result. This looks like:

Query q = em.createNativeQuery(
    "SELECT c.id, c.name, COUNT(o) as orderCount, AVG(o.price) AS avgOrder " +
    "FROM Customer c " +
    "JOIN Orders o ON o.cid = c.id " +
    "GROUP BY c.id, c.name",
    "CustomerDetailsResult");

@SqlResultSetMapping(name="CustomerDetailsResult",
    classes={
        @ConstructorResult(targetClass=com.acme.CustomerDetails.class,
            columns={
                @ColumnResult(name="id"),
                @ColumnResult(name="name"),
                @ColumnResult(name="orderCount"),
                @ColumnResult(name="avgOrder", type=Double.class)})
    })

或者您可以将FeedDetails转换为接口并尝试使用Spring Data JPA接口投影:

Or you could convert FeedDetails to an interface and try Spring Data JPA Interface projection: https://docs.spring.io/spring-data/jpa/docs/current/reference/html/#projections

或者，如果您不喜欢这些选项，则有一个名为QLRM的小库:

Or if you don't like these option there is a little library called QLRM: https://github.com/simasch/qlrm/blob/master/ConstructorResult.md

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