I want to use Hibernate with previously created java classes and database tables, so I assume (I am a beginer) I must create a mapping including those properties of the class I want to include in the database table.
The problem is when I try to save a new object Hibernate deletes the old table and creates a new one, instead of saving object properties in the previous table columns in a new register. I checked name correspondence between the mapping and table columns and is correct.
What am I doing wrong?
Can I use an Hibernate mapping between a class and a previous table (not created with Hibernate) or not?
Specifics about the class and the table seem irrelevant to me, but I can include one the several examples I have tried if you need it convenient.
Thanks in advance.
Antonio

Hi,

How do you want some help if you don't give the code.... sorry, but it's written with a red background when you write a new post, so...

Even if I am grateful to get an answer, I think you might as well read what I wrote.
This is not a problem about a concrete mapping and a concrete class, but a question about what you can and cannot do with Hibernate (2.1 btw, as the red square asks) and any database (say MySQL).
The real question is: Can you map a previously created class (not using every property of the class in the mapping) to a previously created table (not using every column in the table)? Is a simple question, I only need a yes (and how) or a nope.
Thank you.

Ho... I'm really sorry...

And, for your question, the answer is yes.

And, sorry again...

It was because of this I asked you the source code....

It seems it's my time to apologize.
So here is an example: (Hibernate 2.1, MySQL)
I have a class
public class Centro {
private String prop1;
private String prop2;
private String prop3;
// ... getters and setters
}

and a previous mapping not made with Hibernate to a table with
this structure:
table t_centro
- prop1 : VARCHAR
- prop2 : VARCHAR
- prop3 : VARCHAR

Now I try to do an Hibernate mapping not including prop2 and prop3, only with prop1:

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 2.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd">
<hibernate-mapping>
<class name="saci.Centro" table="t_centro">
<id type="int" column="id">
<generator class="native"/>
</id>
<property name="prop1" column="prop1" type="string" />
</class>
</hibernate-mapping>

When I use

Centro ctr1 = new Centro();
// setting, etc
session.save(ctr1);

I get my previous registers in this table erased in the database, and a new table is created only with id and prop1 columns.

Hibernate log4j says:
11:27:04,742 DEBUG SchemaExport:132 - drop table if exists t_centro
11:27:04,772 DEBUG SchemaExport:149 - create table t_centro (
id INTEGER NOT NULL AUTO_INCREMENT,
prop1 VARCHAR(255)
)
11:27:04,812 INFO SchemaExport:160 - schema export complete

and the end of the story is I lost my previous table and data!
How can I keep my old data while working with the new mapping?

Thanks again.
Antonio

Remove hbm2ddl.auto from your configuration. And probably read up what the configuration options you are setting are doing.

Ok, it solved it.
Thanks for your help, Charles and Michael.
Kind regards
Antonio