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Hibernate version:
3.05

Mapping documents:
<hibernate-mapping>
<class name="Event" table="EVENTS">
<id name="id" column="EVENT_ID">
<generator class="native"/>
</id>
<property name="date" type="timestamp" column="EVENT_DATE"/>
<property name="title"/>
</class>
</hibernate-mapping>

Code between sessionFactory.openSession() and session.close():
Event theEvent = new Event();
theEvent.setTitle(title);
theEvent.setDate(theDate);
session.save(theEvent);

Full stack trace of any exception that occurs:

Name and version of the database you are using:
MySQL 4.1

The generated SQL (show_sql=true):

Debug level Hibernate log excerpt:

I'm a newbie to Hibernate and am following the example at http://www.hibernate.org/hib_docs/v3/reference/en/html/tutorial.html.

I'm confused about the id property of the classes and how it's mapped to a field in the database. I want my table to have an auto_increment primary key, and I want that field mapped to the id field of my Java class. No matter which type of generator I seem to use in the mapping file, my database always auto_increments the PK (1, 2, 3, etc...) but Hibernate always assigns its own values to the id field of my object (4294967297, 4294967298, etc...).

Am I misunderstanding what that id is supposed to be used for? Or am I just not setting up my mapping file correctly?

First of all if you want increment, change the generator class to "increment", secondly does your ddl specify "auto increment" on the id column?

Yes I have the id column set to auto_increment. When I use generator as "increment" it assigns the first row 1, then the second row 16777215, then the third insert gets an exception:

14:39:23,834 WARN JDBCExceptionReporter:71 - SQL Error: 1062, SQLState: 23000
14:39:23,844 ERROR JDBCExceptionReporter:72 - Duplicate entry '16777215' for key 1
14:39:23,844 ERROR AbstractFlushingEventListener:277 - Could not synchronize database state with session
org.hibernate.exception.ConstraintViolationException: Could not execute JDBC batch update
at org.hibernate.exception.ErrorCodeConverter.convert(ErrorCodeConverter.java:74)
at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:43)
at org.hibernate.jdbc.AbstractBatcher.executeBatch(AbstractBatcher.java:181)
at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:226)
at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:136)
at org.hibernate.event.def.AbstractFlushingEventListener.performExecutions(AbstractFlushingEventListener.java:274)
at org.hibernate.event.def.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:27)
at org.hibernate.impl.SessionImpl.flush(SessionImpl.java:730)
at org.hibernate.impl.SessionImpl.managedFlush(SessionImpl.java:324)
at org.hibernate.transaction.JDBCTransaction.commit(JDBCTransaction.java:86)
at EventManager.createAndStoreEvent(Unknown Source)
at EventManager.main(Unknown Source)
Caused by: java.sql.BatchUpdateException: Duplicate entry '16777215' for key 1
at com.mysql.jdbc.ServerPreparedStatement.executeBatch(ServerPreparedStatement.java:642)
at org.hibernate.jdbc.BatchingBatcher.doExecuteBatch(BatchingBatcher.java:57)
at org.hibernate.jdbc.AbstractBatcher.executeBatch(AbstractBatcher.java:174)
... 9 more

Have you tried setting an "unsaved-value" default in the constructor of your pojo and on your id element?

The "unsaved-value" in the contructor & id element did nothing. I still get an id of 1, then 16777215, then an exception.

Is it even possible to have Hibernate assign the id property of your POJO to the actual auto-incremented primary key id field in your database table?!?!

I already have a populated customers table with these fields:
- customer_id (integer, auto_increment)
- customer_name (varchar)

The customer_id field starts at 1 for the first customer and goes up from there to the last customer.

I created a Customer class that has these properties, along with appropriately named getters/setters:
- id (Long)
- name (String)

Now, I want Hibernate to create a Customer object for each row in the customers table, mapping the table fields to these POJO properties:
- customer_id ==> id
- customer_name ==> name

So I put this in the Customer.hbm.xml file:


However, when Hibernate creates the Customer objects, the id's ARE NOT the ones contained in the customers table. They are integers that start at 4294967297 and count up.

Can anyone tell me what stupid mistake or misunderstanding I'm making? I really want to use Hibernate, it looks super-cool, but I can't seem to get it to do this one really simple little thing.

For any other poor newbie like myself who runs into this stupid problem here's the fix:

- declare your id property of your POJO as an int, not a Long as is done in the tutorial referenced above
- use <generator class="increment"/> in the mapping file

Hibernate now correctly:
- uses the existing primary key field to set the value of id in the Customer object
- correctly assigns the id of newly created Customer objects to the next higher value of the primary key when saving the new Customer to the database