Page Comparison

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3. Select the list of APIs to be integrated in the TQL Model (ThingFacets). For this tutorial we have selected API to get temperature, humidity, light, pressure for a given City and Country. 

<current>
  <city id="5393015" name="Santa Clara">
    <coord lon="-121.96" lat="37.35"/>
    <country>US</country>
    <sun rise="2016-03-17T14:13:28" set="2016-03-18T02:18:25"/>
  </city>
  <temperature value="297.67" min="296.15" max="301.15" unit="kelvin"/>
  <humidity value="41" unit="%"/>
  <pressure value="1012" unit="hPa"/>
  <wind>
    <speed value="3.1" name="Light breeze"/>
    <gusts/>
    <direction value="0" code="N" name="North"/>
  </wind>
  <clouds value="5" name="clear sky"/>
  <visibility value="16093"/>
  <precipitation mode="no"/>
  <weather number="800" value="clear sky" icon="02d"/>
  <lastupdate value="2016-03-17T23:30:57"/>
</current>

Write a ThingFacet 

To abstract the interactions with the OpenWeatherMap Cloud Service we write a ExternalEnvFacet ThingFacet.

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Note that the Event Parameter values are dereferenced using TP Notation. The notation [%: is part of the /wiki/spaces/TEACH/pages/21170773. More details on /wiki/spaces/TEACH/pages/21170773 can be found in the Developer's Guide.

[%:Event.Argument.DCBaseURL.Value:%]

DCBaseURL value passed when creating/updating model instance.

[%:Event.Argument.DCQueryParam.Value:%]

DCQueryParam value passed when creating/updating model instance.

&

[%:Event.Argument.OutputFormat.Value:%]

OutputFormat value passed when creating/updating model instance.

[%:Event.Argument.DCAPIKey.Value:%]

DCAPIKey value passed when creating/updating model instance.

4. Process Response.

• Check if HTTP code is 200 else log the error message

• Convert the temperature value from Kelvin to Centigrade.

  Code Block
  language xml title HandleResponse to GET
  <Invoke Name="HandleResponse"> <FacetScript> <If Condition="/'[%:Invoke.ReadValues.Status:%]' eq '200'"> <Then> <Log Message="Response Status is 200"/> <If Condition="/'[%:Invoke.ReadValues.Message.Value.current.temperature.unit:%]' eq 'kelvin'"> <Then> <Log Message="Temperature Unit is Kelvin.."/> <SetContextData Key="CelTemp" Value="[%:/number([%:Invoke.ReadValues.Message.Value.current.temperature.value:%]-273):]"/> <Log Message="Temperature Value in Centigrade is.. [:$ContextData.CelTemp:]"/> </Then> <Else> <SetContextData Key="CelTemp" Value="[%:Invoke.ReadValues.Message.Value.current.temperature.value:%]"/> </Else> </If> </Then> <Else> <Log Message="Non-200 Response Status. Send Alert to DevOps"/> </Else> </If> </FacetScript> </Invoke>

  Tag	Resolution
  "/'[%:Invoke.ReadValues.Message.Value.current.temperature.unit:%]' eq 'kelvin'"	This is an XPath Expression to compare string. Example: "/<StringValue>' eq 'StringValue2'
  SetContextData	This is a temporary key/value storage provided by TQLEngine as part of FacetScript. Here Key is CelTemp, Value is converted value to Centigrade to Original Value (if original value is not in Kelvin).
  [%:/number([%:Invoke.ReadValues.Message.Value.current.temperature.value:%]-273):]	This is XPath Expression to perform Subtraction.

5. Store the output value in EvnDetails Attribute.

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<Query Storage="TqlSubscription">
  <Save>
    <TqlSubscription Label="Changes To External Env" sid="1">
      <Topic>
        *Atomiton.ExternalEnvServiceDeviceCloudProvider.ExternalEnv*
      </Topic>
    </TqlSubscription>
  </Save>
</Query>

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