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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.defined by :
- User Specified Facet ID
- One of the TQLEngine supported Facet Types
- Protocol Handler Name on which the requests will be listening.
Syntax
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<NewFacetInstance fidFid="helloworld" name="HelloWorldUser-specified unique identifier" typeName="SffMsgFacet">Name of the <OnActivate/>Facet <OnOpen ModifyPipelineInstance" Type="HttpServerExtensionArgs"/> <OnRequest> <DoResponse> <Process> <Message type="textFacetType Name"> <Value> Hello World from FacetScript! </Value> </Message> </Process> </DoResponse> </OnRequest> <OnResponse/> <OnClose/> </NewFacetInstance><!-- Blocks of Lifecycle stages --> <OnActivate/> <OnOpen ModifyPipeline="Server-side Name of the Protocol Handler"/> <OnRequest/> <OnResponse/> <OnClose/> <OnError/> </NewFacetInstance> |
Syntax Notes
- NewFacetInstances are defined within NewPackage definition. A package definition consists of a collection of FacetInstances.
- Examples of each of these variations will be provided in the next section.
- Incoming requests without valid facet IDs are rejected.
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.
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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.
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| Event | Description |
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| 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
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<NewFacetInstance fid="helloworld" name="HelloWorld" type="SffMsgFacet">
<OnActivate/>
<OnOpen ModifyPipeline="HttpServerExtensionArgs"/>
<OnRequest>
<DoResponse>
<Process>
<Message type="text">
<Value>
Hello World from FacetScript!
</Value>
</Message>
</Process>
</DoResponse>
</OnRequest>
<OnResponse/>
<OnClose/>
</NewFacetInstance> |
For FacetScript Language specs, see here.