CMP beans

CMP beans - id

Thread view:

Demetz Markus - 07 Dec 2005 10:17 GMT

Hi everybody!

I'm new to CMP Beans, and i want each bean to have a unique id and do the
relationships over id's. But which is the best way to generate id's? I found
the following:

private Integer generatePrimaryKey() {
return new Integer((new Object()).hashCode());
}
is this a good way?
Isn't there another approach to do an autoincrement?

Thanks for any hint!
Markus

Reply to this Message

Viator - 07 Dec 2005 13:30 GMT

There is no guarantee that new Object().hashCode() will always give you
unique numbers. Try using a class (some sort of Sequencer) that gives
you a unique integer and increments it by one with every call.

Amit :-)

Reply to this Message

Bjoern Bredohl - 07 Dec 2005 14:47 GMT

Demetz Markus schrieb:

> private Integer generatePrimaryKey() {
> return new Integer((new Object()).hashCode());
> }

You can use this in jdk 1.5.x
...
setId(java.util.UUID.randomUUID().toString());
...

You can also look for UUID Generator like JUG (http://jug.safehaus.org/Home)

> Isn't there another approach to do an autoincrement?

Yes, there is another possibility. The RDB can autoincrement. But if you
have CMR's you get problems.

Björn

Reply to this Message

Free Magazines

Get these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...