I'm attaching two WARs to demonstrate. foo.war and bar.war are identical except for the message in the resource bundle.

Hit
http://localhost:8080/foo/index.jsp
http://localhost:8080/bar/index.jsp
http://localhost:8080/foo/index.jsp

Both will output the correct message to the browser when the lookup is done from ResourceBundle.getString(). But the log message it sends will not always be correct. "bar" always wins. As soon as "bar" has been called then "foo" can no longer log the correct message.