@Embeddable
public class EmbeddableOne implements Serializable {
   private String field1;
   ...
}
@Embeddable
public class EmbeddableTwo implements Serializable {
   private Boolean field1;
   ...
}
@Embeddable
public class EmbeddableThree implements Serializable {
   private Double field1;
   ...
}

@Entity
public class MyEntity implements Serializable {
   @Embedded
   private EmbeddableOne field1 = new EmbeddableOne();
   @Embedded
   private EmbeddableTwo field2 = new EmbeddableTwo();
   @Embedded
   private EmbeddableThree field3 = new EmbeddableThree();
   ...

   public EmbeddableThree getField3() {
      if (field3 == null) {
          field3 = new EmbeddableThree();
      }
      return field3;
   }
}