CODEWITHSUNDEEP
javahibernatejpa
user8297969
user8297969

Reputation: 455

JPA - An entity's property type depends on a column value

I'm working with a 3rd party database with the following table:

Node
----
id (int not null)
fKey (varchar(max) null)
refTable (varchar(max) null)

fkey is the value of the primary key of refTable. refTable contains one the following values Car, Truck, or Boat. My node entity currently looks like:

@Entity
@Data
public class Node {
  
  @Id
  private Long id;

  @Column(name = "fKey")
  private String foreignKey;

  @Column(name = "refTable")
  private String targetTable;
}

But I'd prefer the node entity refer to a Car entity when targetTable is Car. Something like this:

@Entity
@Data
public class Node {
  
  @Id
  private Long id;

  @ManyToOne
  @JoinColumn(name = "carId")
  private Car car;
  
  // ok with having truck and boat 
  // here too and being null when refTable refers to Car

}

How can I set up this mapping?

Upvotes: 0

Views: 91

Answers (1)

César Alves
César Alves

Reputation: 476

A better aproach would be to use inheritance. You should turn your Node class the MainClass and inherit from it to Car, Truck and Boat

@Entity
@Data
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name = “refTable”)
public class Node {
  
  @Id
  private Long id;

  
  
}

Your subclassed implementation should look like

@Entity
@Data
@DiscriminatorValue(“Car”)
public class CarNode extends Node {
  
  @ManyToOne
  @JoinColumn(name = "fKey")
  private Car car;
  
}

The same for Truck and Boat. Your query for Nodes would return you CarNodes, TruckNodes or BoatNodes

Upvotes: 1

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