What do you mean by "common interface"? JBoss AS comes with several pre-deployed web apps, telling us which url you are looking at would be helpful.
Since you mentioned mbeans, I assume you might be looking at the jmx-console (http://localhost:8080/jmx-console). The source for it is in the source code download for JBoss AS, you might start by looking at that.
By the way, which version of JBoss AS?