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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> <p>
The roster lets you keep track of the availability (presence) of other users. Users The roster lets you keep track of the availability ("presence") of other users.
can be organized into groups such as "Friends" and "Co-workers", and then you A roster also allows you to organize users into groups such as "Friends" and
discover whether each user is online or offline.<p> "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> 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> <br clear="all" /><br><br>