Hibernate with existing databases

Question

I'm trying to build a spring roo project using hibernate and an oracle database. The oracle database contains tables used by another application.

I have an entity User that already exists in the database, containing thousands of users and shared by another application.

My new roo project contains the user entity and also some others. The persistence.xml is configured with the following property:

<property name="hibernate.hbm2ddl.auto" value="update"/>

On the first deployment of the app, hibernate fails because there are no tables for the entities. Changing the value to "create" fixes this, but wipes the user table :(

Is there a way around this? What I would like to do is this

property value is "create" but the User entity is excluded somehow
Deploy application, tables are created etc. Existing User table is used.
Stop application
Modify property value to "update"
No data loss :)

Many thanks.

earldouglas · Accepted Answer · 2011-02-02 17:24:47Z

2

There must be a better way to do this, but here is a quick hack which will get you rolling with your desired steps:

Rename the table in your Hibernate mapping to user_unused
Modify property value to create
Deploy application, tables are created etc, existing user table is unaltered.
Stop application
Rename the table in your Hibernate mapping to user
Modify property value to update
Delete the user_unused database table that was created by Hibernate in step 1

answered Feb 2, 2011 at 17:24

earldouglas

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2 Comments

Karl Walsh Over a year ago

Thanks james, that's what we were doing. Was hoping there was a nicer way, less prone to forgetfulness with the renaming

earldouglas Over a year ago

Another way would be to import the data from the existing user table before recreating all the tables, then repopulate the newly created user table. I'd have to dig into the Hibernate source code to see if there's a way run DDL on a per-table basis.

Neo · Accepted Answer · 2011-02-04 13:35:57Z

0

I remember from some hibernate forum that this feature is not available yet from hibernate. So here is another hack. You may use false for 'creat' and true for 'update'. off-course you would be required to have all classes configured in that case.

answered Feb 4, 2011 at 13:35

Neo

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