Introduction
Facet Instance is a data structure associated with each incoming request to the TQLEngine. Each facet instance is identified by its facet ID and represents a capability to perform certain actions on the TQLEngine. Incoming requests without valid facet IDs are rejected. Each facet instance is also associated with its Facet Type, which is a piece of executable code (a Java class) intended to actually process the request. Facet instances are deployed through packages. A package is a collection of related facet instances.
Facet Instance Lifecycle
Once a request legitimacy is established by successful resolution of its facet ID, a processing (Netty) pipeline is created for low level request processing.
Once request data is presented in a universal fashion (as an instance of ListMap data structure), TQLEngine invokes appropriate facet type method using current connection context and facet instance information as arguments.
The facet lifecycle is the beginning-to-end stages of the facet pipeline that are marked by different facet events. Each facet event can be associated with invoking a method. The actual call arguments will be selected by the TQLEngine by executing the event-specific piece of facet script found in the facet instance. That is, it is possible to specify a correspondent piece of facet script for each facet event. Such facet script may contain simple logic to check some request value or do template-based data transformation before actual java method invocation.
For instance, upon facet instance activation (creation) the TQLEngine will invoke the onActivate method; upon incoming request it will invoke onRequest method and so on.
| Event | Description |
|---|---|
| onActivate | Handler is called by the engine at the of activation of the facet |
| onDeactivate | Handler is called by the engine at the time of deactivation |
| onOpen | Handler is called, when facet pipeline is opened |
| onClose | Handler is called, when facet pipeline if closed |
| onRequest | Handler is called when the request is received on the pipeline |
| onResponse | Handler is called when the response is send on the pipeline |
| onError | If error in pipeline, this handler is called and pipeline gets closed |
Facet Instance Examples
For FacetScript Language specs, see here.