I am running an ejabberd server with a series of locked down multi user chats (members only, registration required, no subject change or PMs permitted etc) One requirement is to strictly identify which users (from their user Id/account Jid when registering with the server) are present in each room, and which user has sent a message.
How this is achieved is not important, it can either be: a) By getting the userId from message.getFrom() b) By getting the nick/resource part from the message sender, and enforcing what nick a user can choose
In direct messages, the Jid of a sender will look like:
<userId>@<domain>/<resourcepart>
so I can take the userId (LocalPart) and not worry too much what nickname was chosen.
This is not possible in multi user chats however, since the Jid will appear as:
<roomName>@conference.<domain>/<resourcepart>
The userId of the sender is not present, so I have to rely on the nickname, but this can be set to anything by the users (and changed at any point in the chat)
Is there a way to enforce how a nick is set? (i.e. set to the same value as userId) or otherwise extract the userId from a multi user chat message?
As I wrote, you need a non-anonymous room. The real XMPP address (JID) of a room occupant will then be part of the participant's presence (XEP-0045 § 7.2.3). You can obtain the presence of a occupant via MultiUserChat.getOccupantPresence(EntityFullJid user). From this Presence you want to extra the MUCUser information via MUCUser.from(presence). From which you extra the MUCIitem which should allow to retrieve the real JID via MUCItem.getJid()1.
1: Note that the javadoc if this method seems to be misleading, it should contain the real JID of the user and not the MUC JID.