/**
* This method is used to apply resource-specific knowledge on the exchange. If the request was
* successful, it sets the Observe option for the response. It is important to use the
* notificationOrderer of the resource here. Further down the layer, race conditions could cause
* local reordering of notifications. If the response has an error code, no observe relation can
* be established and if there was one previously it is canceled. When this resource allows to be
* observed by clients and the request is a GET request with an observe option, the {@link
* ServerMessageDeliverer} already created the relation, as it manages the observing endpoints
* globally.
*
* @param exchange the exchange
* @param response the response
*/
public void checkObserveRelation(Exchange exchange, Response response) {
/*
* If the request for the specified exchange tries to establish an observer
* relation, then the ServerMessageDeliverer must have created such a relation
* and added to the exchange. Otherwise, there is no such relation.
* Remember that different paths might lead to this resource.
*/
ObserveRelation relation = exchange.getRelation();
if (relation == null) return; // because request did not try to establish a relation
if (CoAP.ResponseCode.isSuccess(response.getCode())) {
response.getOptions().setObserve(notificationOrderer.getCurrent());
if (!relation.isEstablished()) {
relation.setEstablished(true);
addObserveRelation(relation);
} else if (observeType != null) {
// The resource can control the message type of the notification
response.setType(observeType);
}
} // ObserveLayer takes care of the else case
}
/**
* Notifies all CoAP clients that have established an observe relation with this resource that the
* state has changed by reprocessing their original request that has established the relation.
*
* @param filter filter to select set of relations. <code>null</code>, if all clients should be
* notified.
*/
protected void notifyObserverRelations(final ObserveRelationFilter filter) {
notificationOrderer.getNextObserveNumber();
for (ObserveRelation relation : observeRelations) {
if (null == filter || filter.accept(relation)) relation.notifyObservers();
}
}