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Initial version of real roster documentation.

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Matt Tucker 2003-09-28 23:08:33 +00:00 committed by mtucker
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@ -16,12 +16,104 @@ Roster and Presence
<p>
The roster lets you keep track of the availability (presence) of other users. Users
can be organized into groups such as "Friends" and "Co-workers", and then you
discover whether each user is online or offline.<p>
The roster lets you keep track of the availability ("presence") of other users.
A roster also allows you to organize users into groups such as "Friends" and
"Co-workers". Other IM systems refer to the roster as the buddy list, contact list,
etc.<p>
A <tt>Roster</tt> instance is obtained using the <tt>XMPPConnection.getRoster()</tt>
method, but only after
method, but only after successfully logging into a server.
<p class="subheader">Roster Entries</p>
<p>
Every user in a roster is represented by a RosterEntry, which consists of:<ul>
<li>An XMPP address (e.g. jsmith@example.com).
<li>A name you've assigned to the user (e.g. "Joe").
<li>The list of groups in the roster that the entry belongs to. If the roster
entry belongs to no groups, it's called an "unfiled entry".
</ul>
The following code snippet prints all entries in the roster:
<pre>
Roster roster = con.getRoster();
<b>for</b> (Iterator i=roster.getEntries(); i.hasNext(); ) {
System.out.println(i.next());
}
</pre>
Methods also exist to get individual entries, the list of unfiled entries, or to get one or
all roster groups.
<p class="subheader">Presence</p>
<img src="images/roster.png" width="166" height="322" vspace="5" hspace="5" alt="Roster" border="0" align="right">
<p>Every entry in the roster has presence associated with it. The
<tt>Roster.getPresence(String user)</tt> method will return a Presence object with
the user's presence or <tt>null</tt> if the user is not online or you are not
subscribed to the user's presence. <i>Note:</i> typically, presence
subscription is always tied to the user being on the roster, but this is not
true in all cases.</p>
<p>A user either has a presence of online or offline. When a user is online, their
presence may contain extended information such as what they are currently doing, whether
they wish to be disturbed, etc. See the Presence class for further details.</p>
<p class="subheader">Listening for Roster and Presence Changes</p>
<p>The typical use of the roster class is to display a tree view of groups and entries
along with the current presence value of each entry. As an example, see the image showing
a Roster in the Exodus XMPP client to the right.</p>
<p>The presence information will likely
change often, and it's also possible for the roster entries to change or be deleted.
To listen for changing roster and presence data, a RosterListener should be used.
The following code snippet registers a RosterListener with the Roster that prints
any presence changes in the roster to standard out. A normal client would use
similar code to update the roster UI with the changing information.
<br clear="all">
<pre>
final Roster roster = con.getRoster();
roster.addRosterListener(new RosterListener() {
<b>public void</b> rosterModified() {
<font color="gray"><i>// Ignore event for this example.</i></font>
}
<b>public void</b> presenceChanged(String user) {
<font color="gray"><i>// If the presence is unavailable then "null" will be printed,
// which is fine for this example.</i></font>
System.out.println(<font color="green">"Presence changed: "</font> + roster.getPresence(user));
}
});
</pre>
<p class="subheader">Adding Entries to the Roster</p>
<p>Rosters and presence use a permissions-based model where users must give permission before
they are added to someone else's roster. This protects a user's privacy by
making sure that only approved users are able to view their presence information.
Therefore, when you add a new roster entry it will be in a pending state until
the other user accepts your request.</p>
If another user requests a presence subscription so they can add you to their roster,
you must accept or reject that request. Smack handles presence subscription requests
in one of three ways: <ul>
<li> Automatically accept all presence subscription requests.
<li> Automatically reject all presence subscription requests.
<li> Process presence subscription requests manually.
</ul>
The mode can be set using the <tt>Roster.setSubscriptionMode(int subscriptionMode)</tt>
method. Simple clients normally use one of the automated subscription modes, while
full-featured clients should manually process subscription requests and let the
end-user accept or reject each request. If using the manual mode, a PacketListener
should be registered that listens for Presence packets that have a type of
<tt>Presence.Type.SUBSCRIBE</tt>.
<br clear="all" /><br><br>