Hi,

If I have an application with uses Hibernate as the persistence layer, what is the best practice to upgrade my application?

For example, I have a class called "User" and its has an attribute "String username". I use hibernate to make this class persistence.

I deploy this version of application and have database populate with data.

But what if in future, I need to add a new attribute "password" in the User class. How can I /or hibernate will still work with the database that I created for the older version? Will hibernate smart enough to add a new column for the new attribute in my User class ?


Hibernate version:
2.1.7
Mapping documents:
N/A
Code between sessionFactory.openSession() and session.close():
N/A
Full stack trace of any exception that occurs:
N/A
Name and version of the database you are using:
MySQL
The generated SQL (show_sql=true):
N/A
Debug level Hibernate log excerpt:
N/A

I doubt that. You will have to upgrade the database yourself, but Hibernate has some tools with which you can export the DDL statements for the creation of your database.

Guys, there is a whole chapter about it in the documentation.

Thanks for the answer.

Could you please tell me which chapter in hibernate documentation talks about it? I have the "hibernate in action" book too, I can't find a chapter which talks about upgrading hibernate application.

Thank you.

Chapter 15. ToolSet Guide (15.1: Schema Generation )
Read through 15.1.5

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Megha

Thank you for your help.

Can you please tell me if/how hibernate supports back compatiblity?

For example, if I have new release of my application uses hibernate and that add/delete an attribute in my persistent object.

If I use Hibernate's tool to update my database scheme to add/remove an extra column in my table, will an older version of my application still works with this new table in my database?

And what will happen if I use my new application to read data from an un-updated database (missing column)?

Thank you.

SchemaUpgrade does not support dropping of columns :-( Its only an incremental add.



Umm sorry but how would a application against a un-matching schema work? What you would probably need to do before your application runs is to begin with an incremental update of your DB with hibernate. This will ensure missing columns your application accesses, are added.

Regarding the dropped columns, if my bean is matched with the hbm, and does not contain the column, my application does not care about it anymore. I am fine with this behaviour. But the DB fields will keep hanging around.. its your decision to make then.


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Meg