First of all the disclaimer: you can brick your Android. Read the warnings before proceeding.
In essence we're going to install a chroot-ed environment in which we run JBoss AS 7 using OpenJDK on the booted (stock) Android Linux kernel.
Install a Debian Distribution
Use Linux Installer to create the chroot environment. Make sure to create a loop file which is large enough to hold the base installation, the JDK and JBoss AS 7 itself.
I used 2GB and ended up with 743MB in use.
Install a JDK
Use your favorite package manager to install a JDK.
# aptitude install default-jdk
Create a jboss user
For security we create a jboss user and switch to it.
Add jboss user
Create a jboss user under which to run JBoss AS 7.
# useradd -m jboss
Add permission for jboss user
By default Android does not allow normal users access to network resources.
# addgroup --gid 3003 aid_inet
# adduser jboss aid_inet
Switch to jboss user
# su - jboss
Install JBoss AS 7
Get JBoss AS 7 and boot it up.
Download and unpack
$ tar zxf jboss-as-7.1.0.CR1b.tar.gz
$ cd jboss-as-7.1.0.CR1b/bin