Exceptions and XMPP Errors

Dealing with Stream Errors

XMPP Stream Errors are unrecoverable, which means the session will get disconnected after they have occurred.

Here’s an example how to react to stream errors.

xmppClient.addSessionStatusListener(e -> {
    if (e.getThrowable() instanceof StreamErrorException) {
        StreamErrorException streamException = (StreamErrorException) e.getThrowable();
        if (streamException.getCondition() == Condition.SYSTEM_SHUTDOWN) {
            // Server was shut down.
        }
    }
});

Dealing with Stanza Errors and Lack of Responses

Most stanza errors are returned in response to an IQ-get or IQ-set query.

For querying another XMPP entity, there’s a query method on the XmppClient class, which queries another entity for information and which is used by most methods.

Now two things can happen:

• The entity does not respond at all.
• The entity returned a stanza error.

In the first case a NoResponseException is thrown, in the latter case a StanzaException is thrown.

If you want to determine, which kind of exception it is, simply ask for their type.

Here’s an example:

try {
    EntityTime entityTime = entityTimeManager.getEntityTime(Jid.of("juliet@example.net/balcony")).getResult();
} catch (NoResponseException e) {
    // The entity did not respond
} catch (StanzaException e) {
    if (e.getCondition() == Condition.SERVICE_UNAVAILABLE) {
        // The entity returned a <service-unavailable/> stanza error.
    }
} catch (XmppException e) {
    // everything else
}

As you can see asking for the type and then for the specific condition gets you where you want.

Btw: If you wonder, why the error conditions aren’t represented as enum, it is because some error conditions like <gone/> have additional data.