For a deeper understanding, please refer to the official hibernate documentation
<class name="com.magicmonster.intranet.users.businessobjects.UserBO" table="users"> <id name="id" type="long" column="id"> <generator class="sequence"> <param name="sequence">users_s</param> </generator> </id> <property name="password"/> <property name="username"/> </class>
When a new user object is added to the user table, the users_s sequence is used for the id column.
Even though it is an integer in the database, we use type="long".
The UserBO javabean must have a Long object property.
If the bean's property names are different to the table columns, you must use something like this:
.. .. <property name="startDate" column="start_date"/> <property name="endDate" column="end_date"/>
startDate is the bean property, and start_date is the database table column
Using hbm2ddl, to create the ddl from the hibernate xml configuration files, I ran into the problem of having a sql datetype of timestamp in postgresql, when the java type is a Date.
The java Date object contains information such as date, time, timezone, milliseconds. If you only need a plain date comprising of a day, month and year, then use the type attribute to specify the sql datatype.
<property name="accountingDate" column="accounting_date" type="date"/>
If you don't do this it defaults to a timestamp. When it did default to this, in postgresql it was a timestamp without a timezone, and hibernate tried to insert timezone information along with the timestamp.