Splunk can index SOAP envelopes: they are just plain text. For instance, you could set jboss to trace the soap requests it is serving to file, then collect it with splunk.
You could assign that data a sourcetype which has the props.conf's **KV_MODE=xml** setting to automatically extract the fields at search time. Also, you could use multiple SEDCMD configs to strip the SOAP tags rightaway (unless you like to report on the xmlns you are using the most 🙂
