Hi,
This is my first time on this forum. Hope to get some solution to a small problem I am facing with Hibernate.

I have a Oracle table (lets say T) whose primary key is, lets say, P. While storing records in this table I use the <generator> for "P", which uses oracle's "sequence". This works fine.

In this table, I have to add another column, lets say Q. Although this new column will hold unique values for each record (and behaves like a primary key), yet it should not to be part of any key in "T". So far so good.
But my problem starts now:
1. Column Q should be "sequence" driven. I have created a new sequence for this. But I don't know how to use this sequence in the <property>. I am not sure if two sequence generators (one for P and one for Q) are allowed in one mapping xml. I need help here.

2. Column Q's final value should be a "function" of this new sequence. This new sequnce will return a numeric value (everytime unique). Using this unique number I have to create a unique string and then store that string value in the Q column. Again, I don't know how to do this and need help.
note: I have the logic available for this function. All I need to know is "can I", and "how to" use it in hbm mapping document ?

Thanks,
Sumit

1. where's your sequence stored?

2. Would you be better off having a get method which returned the generated sequence value and set it as a normal property if it's based on another value? You could do the (painful) 'if not null then generate else return' for new or current entries, so it only calculates for new objects

obvious issue is you won't have an id for a new object. I have come across the DefaultSaveOrUpdateEventListener object in hibernate which allows you to run code as the save occurs, but whether you'd be able to get a handle on the id at that point is another matter that i'm afraid i can't answer without looking into it.

However, going on the assumption that your new unique value cannot be null, i don't think you'll ever have a handle on the id value until after the object has been saved, by which point your second unique key will still be null.

I'm assuming you have a good reason (or a need) to have two unique keys rather than one? If it's purely for use within the code rather than the db, would it not be easier to generate it in the code when your code needs it, as at that point you would have your unique id available?