This article applies to 123-reg servers running Plesk.
To use Tomcat from the Plesk Power Pack for executing Java Servlets on your server you will need to start the service and ensure it is enabled for subscriptions that require JSP support.
Login to your Parallels Plesk Panel.
Click on the Tools & Settings link on the left panel.
Under the Server Management section click on the link Services Management.
On the Services Management page click on the green start icon for the Tomcat Java service.
You will now need to enable Tomcat on a subscription.
Click on the Subscriptions link on the left panel.
Click on the Domain Name link for that you wish to allow Tomcat for.
Select the Customize tab from chosen domains subscription page.
Click on Show more available resources to display more choices.
Use the tick box to allow unlimited Java applications, or place a number in the field provided.
Scroll to the bottom of the page and click on the Update & Lock button to complete the process.