it's possible to install a java library on a server with rad hat 6.2 and plesk 1.3.1 ? If yes, how?

I need the answer to this very question.Anybody pls.

Yes, you can install jdk then any java servlet container (jserv,
tomcat) standalone from apache or as apache dso module. You need refer
to documentation on container that you choose to know about how it
should be installed.

Also, if you have any additional questions you contact us at Plesk at support@plesk.com - we will be happy to help you.