Hi everyone,
I'm working in a small enterprise where a unified web-based framework is used to handle employee and organizational requests / operation. My organization wants to develop a JAVA Application Server as middle-ware to act as a proxy between local applications (like employee enter\exit registration) and our Data Severs to increase security measures. I should mention that the clients are standalone Java and C# programs sending and receiving data over HTTP & XML.

Since I am completely new to the field of Java Application Servers, I would appreciate any advice on where to begin with. Some basic functionality I digged out are as bellow:

Load Balancing and Caching for the requests (since there could be hundreds of thousands of requests per day)
Handling inbound & outbound requests (usually HTTP)
etc

After searching for few days and reading various topics I am confused if I should use an open source service like JBoss or write the code from bottom up. Any suggestion or advice on where I should begin?