CODEWITHSUNDEEP
hibernatejpajoincolumn
EtherealDeath
EtherealDeath

Reputation: 33

How to join separate table data column in Hibernate

Is there any possible variant to insert data from another table into Hibernate entity. For example we have the following DB-model:

ItemTable:
ITEM_ID NUMBER not null,
ITEM_NAME VARCHAR2,
I_OBJECT_ID NUMBER;

ObjectTable:
OBJECT_ID NUMBER not null,
OBJECT_NAME VARCHAR2;

And the following java-code:

@Entity
@Getter
@Setter
@Table(name = "ITEMTABLE")
public class ItemDTO {

   @Id
   @Column(name = "ITEM_ID")
   private long id;

   @Column(name = "ITEM_NAME")
   private String itemName;

   @Column(name = "I_OBJECT_ID")
   protected long objectId;

   **//TODO: here we need OBJECT_NAME column form ObjectTable**
   private String objectName;

}

So we need just one column not the whole ObjectTable entity for objectName prop.

I've tried construction like:

@JoinTable(name = "OBJECTTABLE", joinColumns = {
        @JoinColumn(name = "OBJECT_ID", referencedColumnName = "I_OBJECT_ID") })
@Column(name = "OBJECT_NAME")

But it fails with:

oracle.jdbc.OracleDatabaseException: ORA-00904: "ITEMDTO0_"."OBJECT_NAME": invalid identifier

Every example of @JoinTable or @JoinColumn assume that I need to include another entity as a prop which will be redundant and slow.

Can this be solved in any way?

P.S. just two cents about why I do not want include second entity into first one, is because I want my JpaRepository will allow me to sort/filter directly over joined column.

Please advise.

Upvotes: 1

Views: 2128

Answers (1)

zforgo
zforgo

Reputation: 3263

Using @SecondaryTable annotation it's easy to map multiple tables to the same entity. More precisely JPA joins the primary table with the secondary table and populates the fields.

@Entity
@Table(name = "ItemTable")
@SecondaryTable(name = "ObjectTable", pkJoinColumns = 
    @PrimaryKeyJoinColumn(name = "OBJECT_ID", referencedColumnName="I_OBJECT_ID")
)
public class ItemDTO {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "ITEM_ID")
    Long id;

    @Column(name = "ITEM_NAME")
    String name;

    @Column(name = "OBJECT_NAME", table = "ObjectTable")
    private String objectName;

}

@Entity
@Table(name = "ObjectTable")
public class ObjectsEntity {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "OBJECT_ID")
    private Long id;


    @Column(name = "OBJECT_NAME")
    private String name;
}

BTW: In the question the names of the columns and tables are different in the data model and the @Table and @Column annotations. It should be consolidated.

Upvotes: 1

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