In WebSphere 6 environment, validation xml file loading fails with an IllegalArgumentException:
...
Caused by: java.lang.IllegalArgumentException: URI scheme is not "file"
at java.io.File.<init>(File.java:364)
..
Musachy applied a fix to trunk, but it is missing in 2.0.5, breaking Struts 2.0.11.2 in said environment.
See also:
https://issues.apache.org/struts/browse/WW-2709