Compound keys in JPA

I want to make an entity that has an autogenerated primary key, but also a unique compound key made up of two other fields

Example:

@Entity

@Table(name = "dm_action_plan")

public class ActionPlan {

    @Id

    private int pk;

    @Column(name = "command", nullable = false)

    private String command;

    @Column(name = "model", nullable = false)

    String model;

}

I want to make a compound keys ("command", "model") as index, 

The Solution is @UniqueConstraint Annotation.

@Entity

@Table(name = "dm_action_plan"

       uniqueConstraints={@UniqueConstraint(columnNames={"command","model")})

public class ActionPlan {

    @Id

    private int pk;



    @Column(name = "command", nullable = false)

    private String command;



    @Column(name = "model", nullable = false)

    String model;

}
It's at all.