When some of the fields in the object is nullable, it should not be in primitive type but in object type, like Long instead of long.

I generate a dataobject with key in long type, and being "assigned", as the following

<id
name="thekey"
type="long"
column="ID"
>
<generator class="assigned" />
</id>

I use hbm2java to generate the corresponding java class. The generated class is as the following

/** identifier field */
private Long thekey;

I wonder why it generats Long instead of long (since the primary key is not nullable). Also, i find that when the key is "identity" instead of "assigned", it will then generate long. Can anyone help to explain why hbm2java has such behavouir? Any reasoning behind? what if I change to long manually?

It's todo with the unsaved value that hibernate uses to determine whether an object is a brand new object or an existing object that has been changed.

http://www.hibernate.org/hib_docs/reference/html_single/#or-mapping-s1-4

I don't know much about hbm2java but I would speculate changing this to a value such as 0 or -1 or "any" or "none" would cause a long to be generated. Try it and see what happens.

You should read this section

http://www.hibernate.org/hib_docs/reference/html_single/#manipulating-data-s8

to make sure you understand the consequences of changing this setting.

Cheers.

Myk.