Two things.
One, on Windows you can not simply "exec" a BAT file, you need to feed it to COMMAND.EXE. On Unix, you can do that with a shell script, but not on Windows. That could well be the primary problem you are having.
In answer to your actual question about the API, asadmin (and the GUI console) both rely on "AMX" beans, which are basically specialized JMX beans. So, if you want to, you can write a Java class that talks to the AMX beans directly to do what you want to do.
https://glassfish.dev.java.net/javaee5/amx/
[Message sent by forum member 'whartung' (whartung)]
http://forums.java.net/jive/thread.jspa?messageID=262106