Ok, I've reverse-engineered a database, generated hbm.xml, pojo and dao classes - so far so good.
Most of the columns in my database are strings, hence most fields in my pojo classes are java.lang.String.
I've also got some presentation code responsible for showing the user this data and accepting changes from the user. This code needs to know how many characters the user should be allowed to enter for each string.

Question: How do I find out how many characters I'm allowed to put in a String field?

The database knows - I'll get an exception if I try to persist strings that are too long - and the reverse-engineering tools could know (the database meta-data tells them) - but the pojo classes don't contain any "public static final int fieldLength_XXX" attributes or similar.
I'd guess that one can probably access this information in the template code, but I'm not 100% sure if it's possible, or how to do this. My hope is that I could make my templates access this information and put that into my generated code, but I've not found the information anywhere.

Is this possible? If so, how? If not, is there a good reason why I shouldn't want this?

Thanks,
Peter

Hibernate tools version: 3.1.0_BETA4

something like: configuration.getClassMapping("someName").getProperty("yaProperty").getColumn(0).getLength() ....non tested but you get the picture.



some would argue that hardcoded constants into your pojo's about length is bad practice. I would instead generate interface with these constants ifi were you.

it has been in jira with a patch for the ooold tools, but noone have had the will to do it for the new tools. feel free ;)

Aha! After some stumbling around in the dark, I'm now getting somewhere.
There isn't a getColumn(int) method (in the version of Hibernate I'm using - 3.1.0 I think), but there is a getColumnIterator(), which amounts to much the same effect.
I can now obtain the data I'm after BUT it means hanging on to the configuration object.

Given a Session, is it possible to get back to the Configuration object from which the Session was created?
I know you can get the SessionFactory from a Session, but I don't see any way of getting the Configuration from that.

(I think I'm going to end up adding methods to do this sort of stuff to my DAO Java classes - I agree that POJO is not the best place, but I think the auto-generated code should make it easy for user-code to access this information)

no, you cannot get from a SF to a Configuration. A SF is a "compiled" version of a Configuration. The Configuration is mutable thus not really good to keep around in the API.

but that does not prevent you from accessing it.

So, given a Session (which is what I generally have available in my code), how can I find out how many characters I can put in text fields?
You're saying that it's not normal to have a Configuration object available as it's mutable, but if one only has a Session or SessionFactory, one can't get at the metadata.

Sounds like a bug or shortcoming in SessionFactory to me.

Am I being unreasonable? Are there better ways of ensuring data validity that don't require the Configuration object?

nothing prevents *you* from keeping it around.

It would just not be a safe/good thing for us to keep around in the API since it is non-safe.

Ah, yes. Understood now.