Testing the availability of external system (ldap, database...) during the startup of Tomcat

Hi, whe have developped a webapp based on spring, hibernate with tomcat 6

We have some tests during the integration process (hudson) that verify that every external system is available.

For example, we are using with spring ldap a specific adress for the ldap server.

The production team must change those parameters (password.). And sometimes they are wrong...

I would like to know what is the best way to verify during the startup of Tomcat that THIS ldap WITh his actual configuration is ok.

I want Tomcat to fail as soon as possible if those external systems (here the ldap) are wrongly configured or not available (proxy...).

I know how to do it with the ldap server.
I'm looking for a the best pattern to verify them, not especially with a ldap server (using a tomcat listener? any pattern?)

Thanks in advance for your help.