[FIXED] Get data from another table which is part of join in Hibernate

Issue

I have a table say A and table B. I wrote a query.

String s="select * 
from A fch 
inner join B ht on A.columnA  = B.columnB
where columnD = 'ASDERT'
and 
columnE = true 
order by columnDate asc;";

I have a hibernate class for table A and table B separately. The issue is from the result set of

rdsSession.createNativeQuery(s).setParameter("columnD", columnD)
                .addEntity(A.class).list();

this query I want to get some values from table B also. I have a class with variables as column names in table B. Do we have something as ResultSet in Hibernate so that I can use the column values of table B particularly?

Solution

You should read into how ORM mappings work and in particular how you can use association mappings for this. Your mappings could look like this:

@Entity
public class A {
  @Id
  @GeneratedValue 
  Integer id;
  @ManyToOne(fetch = LAZY)
  @JoinColumn(name = "columnA")
  B b;
}

@Entity
public class B {
  @Id
  @GeneratedValue
  @Column(name = "columnB")
  Integer id;
  String columnD;
  boolean columnE;
  LocalDateTime columnDate;
}

And then all you'd have to do is execute this HQL query:

List<A> list = rdsSession.createQuery("from A a join fetch a.b b where b.columnD = :columnD and b.columnE = true order by b.columnDate", A.class)
  .setParameter("columnD", columnD)
  .getResultList();

Using a native query requires you to use the same mapping, but then you would also have to add a join result, which also requires a slightly different SQL query:

List<A> list = rdsSession.createNativeQuery("select {a.*}, {b.*} from A a join B b on a.columnA  = b.columnB where columnD = :columnD and columnE = true order by columnDate", A.class)
            .setParameter("columnD", columnD)
            .addEntity("a", A.class)
            .addJoin("b", "a.b")
            .list();

Answered By - Christian Beikov
Answer Checked By - Senaida (JavaFixing Volunteer)