help with inserting data on postgresql on tomcat4

I am using Tomcat4  and connecting postgresql via a source -compiled jdbc
driver for postgreswl 7.2.
I have no difficulty doing a SELECT on a database table  using both a jsp or
a servlet.  I am not able to   INSERT data into the table using a jsp.  I
have not tried to insert  data using a servlet..

Help  on data insertion would be appreciated.

sibu