How to Model a Lookup Table with Composite Key using JPA

Question

I have the following situation with a composite key in a lookup table:

LU_MASTER_TABLE
- [PK1] TYPE = type of value being looked up
- [PK2] ID = id of the value to lookup applying to that table
- DESC = the description of the id.

TABLE2>
- TYPE_A_ID
- TYPE_B_ID

What is the best way to create a one to one relationship using Spring JPA?

Answer 1

So far, below is the best I can come up with. Though it does not use the composite key so while it works, it doesn't really represent the DB structure.

 @Entity
 @Table(name= "LU_MASTER_TABLE")
 public class LuMasterTable {

   @Id
   @Column(name = "ID")
   protected String id;

   // Note I did not make typeField a PK even though it is in DB. 
   // Ideally it would be part of composite key, 
   // though I wasn't able to get composite key to work given 
   // the scenario here where upon joining with another table,
   // it must be a type of "constant".  See where clause in other
   // table below to see what I mean.
   @Column(name = "TYPE")
   protected String typeField;

 }

table2

@Entity
@Table(name = "TABLE2")
public class Table2{

 ...

  @OneToOne
  @JoinColumn(name="TYPE_A_ID")
  @Where(clause = "typeField = TYPE_A")
  protected LuMasterTable typeALuMasterTable;

  @OneToOne
  @JoinColumn(name="TYPE_B_ID")
  @Where(clause = "typeField = TYPE_B")
  protected LuMasterTable typeBLuMasterTable;

}