import javax.persistence.AttributeConverter;

public class TaskConverter implements AttributeConverter<TaskType, String> {

	@Override
	public String convertToDatabaseColumn(TaskType attribute) {
		if (attribute instanceof TaskType1) {
			return "TASK1";
		} else if (attribute instanceof TaskType2) {
			return "TASK2";
		} else if (attribute instanceof TaskType3) {
			return "TASK3";
		}
		return null;
	}

	@Override
	public TaskType convertToEntityAttribute(String dbData) {
		if ("TASK1".equals(dbData)) {
			return new TaskType1();
		} else if ("TASK2".equals(dbData)) {
			return new  TaskType1();
		} else if ("TASK3".equals(dbData)) {
			return new TaskType3();
		}
		return null;
	}

}

      @Embeddable
	public static class Id implements Serializable {

               @Column(name = "task_type_cd")
		@Convert(converter = TaskConverter.class)
		private TaskType taskType;
//getter and setters
}