Say i've an entity by having an auto produced primary key. If i attempt in order to save the entity with values of other fields which might not be unique. The entity will get auto populated using the id from the row got placed. How made it happen acquire that primary key value?
When the primary key column is say identity column whose value is completely made the decision through the database. Therefore it does an place statement without that column value and also the db decides the worthiness to make use of will it communicate back its decision (I dont think so)
Hibernate use three way of removing the DB auto produced area based on what's support through the jdbc driver or even the dialect you're using.
Hibernate extract produced area value to place it in the pojo :
While using method Statement.getGeneratedKeys (Statement javadocs)
Placing and choosing the produced area value from the place statement. (Dialect Javadocs)
Performing a choose statement following the place to retrieve the produced IDENTITY value
All this is accomplished internally by hibernate.
Hope it`s the explication you're searching for.
This portion of the Hibernate documentation describes the car generation of ids. Usually AUTO generation technique is employed for maximum portability and presuming that you employ Annotations to supply your domain metadata you are able to configure it the following:
@Id @GeneratedValue(strategy=GenerationType.AUTO) private long id;
Anyway the provided link ought to provide all of the detail you'll need on produced ids.
Whenever you create an item using the, say, sequence-derived surrogate primary key, you pass it towards the Hibernate session with this area set towards the value that Hibernate translates as "not designated", automatically . This area isn't populated using the designated value before the corresponding record isn't placed in to the database table. You are able to trigger insertion by either clearly calling flush() around the hibernate session or carrying out a database read within the same session. Then you're able to check the need for that area and it'll be designated instead of .