Probably it could be some jboss configuration parameter, take a look at this
jboss forum post.
Seems that DatabaseServerLoginModule can\'t get the correctly-encoded username and must be configured org.apache.catalina.authenticator.FormAuthenticator in order to get utf-8 encoded username.
Some
uri to configure vale.
Add context.xml to /WEB-INF/ and deploy to my jboss server. Now the username can be fetched correctly now and my users can use UTF-8 characters in their login id;
the context.xml must be:
<Context>
<Valve
className=\"org.apache.catalina.authenticator.FormAuthenticator\"
characterEncoding=\"UTF-8\" />
</Context>
Note I\'ve not tried it on my testing environment, but seems it could be the solution to the problem.