Many web services require consumers to specify known IP addresses that their requests will originate from to prevent abuse and attacks from the wider Internet. This is commonly referred to as "IP whitelisting". Due to the scalable nature of Bluemix, the IP address of your Bluemix app will frequently change as you deploy and scale making it impossible to guarantee your IP address ahead of time. Statica solves this problem by offering a proxy service with guaranteed static IP addresses.
Bluemix is great because you can simply push your Java EE application (WAR or EAR) and select what services your application needs. You don't have to worry about the server configuration because it's generated for you by the Liberty buildpack. Ideally, you should write your application in such a way that the generated configuration works for your application. But if you need to enable a Liberty <feature>, set a JVM argument in jvm.options, or provide a shared library that resides outside the WAR, this video explains how to modify server.xml, package your server, and deploy it to Bluemix.