void setPayload(Element payload) {
        this.payload = payload;
        // Update XML representation of the payload
        if (payload == null) {
            payloadXML = null;
        } else {
            payloadXML = payload.asXML();
        }
    }
Sets the payload included when publishing the item. A published item may or may not
have a payload. Transient nodes that are configured to not broadcast payloads may allow
published items to have no payload.

@param payload the payload included when publishing the item or {@code null}
       if none was found.
xmppserver/src/main/java/org/jivesoftware/openfire/pubsub/PublishedItem.java