Spring data JPA only one composite key is auto incremented issue

Question

I am using MySQL database.

In my table i there are two four primary keys, out of which one is auto incremented.

@Embeddable
    public class Employee         


        

Answer 1

Your JPA @Id does not need to match the database PK column(s). So long as it is unique then that is all that matters.

From https://en.wikibooks.org/wiki/Java_Persistence/Identity_and_Sequencing:

The JPA Id does not always have to match the database table primary key constraint, nor is a primary key or a unique constraint required.

As your an auto-increment column is guaranteed to be unique then just use gender_key as your @ID and map id as a normal column.

@Entity
@Table(name = "employee")
public class employee {

   @Id
   @GeneratedValue(strategy = GenerationType.IDENTITY) 
   private int genderKey;

   @Column
   private int id;

}

To be honest I would find your schema confusing however.

I would also suggest reading the following:

https://www.javatpoint.com/java-naming-conventions

Answer 2

You're missing a @GeneratedValue at the id field. Depending on its values, you're free to choose a strategy for generation, like a sequences, id tables, an automatic internal id generation. Last but not least GenerationType.AUTO will choose one of the mentioned strategies. See the Javadocs for javax.persistence.GeneratedValue and javax.persistence.GenerationType.