Two things to keep in mind. First, the "current directory" for any code running in JBoss AS is jboss_home/bin, so all relative file lookups will be relative to that directory. Second, any filename starting with a "/" or "\" is assumed to be an absolute file path on the same disk as JBoss AS. For example, is you really gave the filename "\models\xyz.txt", and JBoss AS is running on the D: driver, then the file's path is "d:\models\xyz.txt"
If that does not help, please tell us the full path location for your file, and post the code you are using to access that file.