Try to set URIEncoding in {jboss.server}/deploy/jboss-web.deployer/server.xml.
Ex:
<Connector port="8080" address="${jboss.bind.address}"
maxThreads="250" maxHttpHeaderSize="8192"
emptySessionPath="true" protocol="HTTP/1.1"
enableLookups="false" redirectPort="8443" acceptCount="100"
connectionTimeout="20000" disableUploadTimeout="true" URIEncoding="UTF-8" />