gistfile1.java

// Mit @IdClass

@Entity
@IdClass(MyPK.class)
public class MyEntity {
  @Id String first;
  @Id String second;
}

public class MyPk {
  String first;
  String second;

  // Getter / Setter
}

// Mit @EmbeddedId

@Entity
public class MyEntity {
  @EmbeddedId MyPk key;
}

@Embeddable
public class MyPk {
  String first;
  String second;
}