Question

i am using hibernate for a application.I have two tables with many-many relationship and I have POJOs for both of them.But the relationship is defined in third table which doesnot have POJO.How can i relate my two tables and use them

Answer 1

Suppose you have POJO for TableA and TableB and want to associate many-to-many relationship between them in Table C without creating POJO for TableC.

If Table C ONLY contains two columns which have the foreign key constraint to Table A and Table B , you can achieve it by using the @ManyToMany and @JoinTable:

@Entity
public class TableA{

  @ManyToMany
  @JoinTable(
        name = "TableC",
        joinColumns = {@JoinColumn(name = "TableA_ID")},
        inverseJoinColumns = {@JoinColumn(name = "TableB_ID")}
  )
  private List<TableB> tableB= new ArrayList<TableB>();

}

@Entity
public class TableB{

  @ManyToMany(mappedBy="tableB")
  private List<TableA> tableA= new ArrayList<TableA>();

}

But if Table C contains more additional columns that have no foreign key constraint to other tables (such as the column for last_modified_date) , you cannot do it and you must declare Table C as a POJO and model the many-to-many association as two one-to-many associations to Table C.