I have searched the online documentation exhaustively (is that a word?) and I finally went out and bought a Hibernat book and I have yet to find any clear and definitive examples of mapping an array in a hibernate xml document. Specifically, I am trying to map arrays of Strings and arrays of doubles. It seems that the documentation takes you to a certain point in doing this and then just drops you. I can't get a clear answer from anyone what tags to use. After playing around with it a bit, I finally got my xml map file to the point where it at least parses but I'm still getting errors when I try to map these elements. Can someone give me a clear example of mapping an array of Strings? Or an array of doubles? I am starting to believe that it has never been done!! This is so frustrating! If someone can help me, I'll give you all my credits!!

Why not just use a List of strings, which is more flexible anyway -- the mapping for this is straightforward. If you really need to map a "String[]" array, you may have to revert to a custom mapping.

Because all of the source code is written with static arrays and it has been decided that it will stay that way

How was it done before? I'm sure the app didn't just stuff an entire array into a single column, because that isn't even 1NF, so each array element must be somehow stored individually. If that's true, then mapping each element is just a straight application of Hibernate basic value type mapping.

But should your app be completely whacked, you're more than welcome to post some sample code/mapping here.


jd

I guess, you might be able to do this with a UserType.

Otherwise, you'll probably have to resort to DTO (data transport objects) in which you load your data from the db using lists and then copy the data to your real objects.

The main question to ask is.


How is the data currently stored in the databse, how is it currently accessed etc.


Sarah, if you could supply us with the schmea, more info on data storage there is a higher chance we may be able to help you.

Also, are you working for a sonar firm that sells it's products through an agent called tritech? Just some of the code you've posted seems familiar.

I'm going to answer all these posts with one entry to save time:

jd001982:

*** Yes, it is "stuffed" into a single column as an array declared float8[] and char(256)[]

hhuber:

*** I believe this is the solution we are going to use, we will have to convince the team that it is the way to go and then create the methods to do the copying. I think it will be a lot better than creating a bunch of tables to hold the arrays and then mapping them back to the parent table ***

Jaimie:



*** It is stored as float8[] and char(256)[] -- one dimensional arrays in a column of the database ***



*** No, I don't work this firm :-) ***

Ouch!!
But what database are you using that allows this?
Is the column a BLOB or VARCHAR?
What did the old code do to write the 8 floats into this column?

Hibernate obviously doesn't let you map array to column, but you can always write a stored procedure to do this, and map the SP as shown in 17.4. Custom SQL for create, update and delete.

jd

You can do this by writing a UserType.

Then you have another option: Use a UserType.
I'm sure you can write up an implementation that converts from the column value to the array and the other way round.

Again, I will answe all these ensuing posts with a single reply to save time:

jd:


Hibernate obviously doesn't let you map array to column, but you can always write a stored procedure to do this, and map the SP as shown in 17.4. Custom SQL for create, update and delete. .[/quote]

Well jd, it is Postgresql and it is a char. I'm not sure how the original data was mapped into this column. I haven't looked at the code yet that does it. I'm sure I will get to that point sometime soon.

gavin:



Gavin, I was hoping not to have to get into user types yet since I have just started using Hibernate and I'm taking it one small step at a time, but thanks, I will probably look into this too.

Thanks for all your feedback! I wish I had more credits to give out! I need to start earning some!