----- Quoting Message from Himadri ----- > All Entities extends EntityBase which has common attribute like id and > version. Do you think this is not a good way to implement ?
This could be a terrible, ghastly way to implement entities. It forces every table to have the same kind of "id" column. I assume you defined "id" as a long (or int or corresponding wrapper class) mapping to an autogenerated sequence surrogate key. Leaving aside the debate whether such a surrogate key is ever a good idea, there certainly are cases where it's a horridly bad idea. Such cases include many-to-many linking tables and subordinate tables with a foreign key reference back to their parent table. Unless I'm mapping to tables that inherit from other tables, I prefer not to have entities inherit from parent entity classes. There just isn't enough of an "is-a" relationship in the application object model to justify the practice. Entity classes are supposed to form an object model, not a data model. Creating inheritance hierarchies to reflect a purported database design is backwards thinking. It can even lead to a change in the data model to match the mapping model, an egregious mistake. I've seen this, where the data-interaction classes assumed a 'Long' id key field and the middleware team forced the data modelers to add such a column where the db design didn't call for it. I recommend to keep entity classes POJO, to abandon falsely-economical inheritance notions, and to design objects to support the object model, not the data model. -- Lew Bloch
