Question

我在Hibernate中遇到了一个非常特殊的嵌套连接查询场景，应该相当简单，但我在缩小数据集方面遇到了麻烦。

我有一个如下表结构：

top                bottom             common
------------       ------------       ------------
id                 id                 top_id 
...                ...                bottom_id
...                ...                common_value
lastUpdated        lastUpdated        date_added

目标是查询它，以便获得具有以下结构的对象：

top: 
{ "id": 1, 
  "lastUpdated": "2016-05-01",
  ...
  "bottom" : [ {
     "id": 1
     "lastUpdated": "2016-01-01",
     ...
     "values": [ {
         "top_id": 1,
         "bottom_id": 1,
         "common_value": "abc",
         "date_added": "2016-05-15"
     } ]
  } ]
}

为此我有这些关系：

@Entity
@Table(name = "top")
public class Top {

    @Id
    @GeneratedValue(strategy = IDENTITY)
    private Long id;

    private String name;
    //...other fields...
    private Date updatedOn;

    @OneToMany(fetch = FetchType.EAGER)
    @JoinTable(name = "common",
                joinColumns = @JoinColumn(name = "top_id"),
                inverseJoinColumns = @JoinColumn(name = "bottom_id")
    )
    private Set<Bottom> bottomSet;

}


@Entity
@Table(name = "bottom")
public class Bottom {

    @Id
    @GeneratedValue(strategy = IDENTITY)
    private Long id;

    private String name;
    //...other fields...

    @OneToMany(fetch = FetchType.EAGER)
    @JoinColumn(name = "bottom_id")
    private Set<Common> values;

}

@Entity
@Table(name = "common")
public class Common {

    @EmbeddedId
    @AttributeOverrides({ @AttributeOverride(name = "top_id", column = @Column(name = "top_id") ),
            @AttributeOverride(name = "common_value", column = @Column(name = "common_value", length = 32) ),
            @AttributeOverride(name = "date_add", column = @Column(name = "date_added", length = 19) ),
            @AttributeOverride(name = "bottom_id", column = @Column(name = "bottom_id") ) })
    private CommonId id;

}

@Embeddable
public class CommonId {

    private Integer top_id;
    private String common_value;
    private Date added_date;
    private Integer bottom_id;

}

结果是结果结构包含了bottom_id所喜欢的所有值，结果太多了。我怎样才能使common_values的底部连接绑定到bottom_id和top_id？

非常感谢您的想法！

Answer 1

解决了 -

关系没有改变，但是我没有查询所有顶级项目，而是创建了以下HQL来关联ID：

FROM Top t 
INNER JOIN FETCH t.bottomSet b 
INNER JOIN FETCH b.values v
WHERE t.id = :topId AND v.id.top_id = :topId

Hibernate Multiple Join使用公共表

1 个答案: