Struts: Fail to connect MySQL after modifying JSP Layout

[PC Leung]

Hello all,

Whenever I modify the JSP layout only,
then I undeploy the original
and deploy the new war file with Tomcat manager.

It fails to connect MySQL.
If I shutdown and startup the Tomcat again.
It is OK to connect MySQL.

Is it the problem of Struts or Tomcat configuration?
I only modify the layout.
Deployment does not show any error message.

MySQL: 4.0
Tomcat: 5.0 (with connection pooling)
Struts: 1.1