Output Templates

Some outputs support templates to control how output data is formatted. This is useful for example when communicating with a SOAP endpoint. The REST Connection Output’s Template setting can be configured to send the endpoint a custom XML payload versus the default JSON payload.

The ‘Template’ setting for these Outputs uses Apache FreeMarker to provide this control.

Apache FreeMarker Special Values

• ${value}

  • The value being written out. By itself this evaluates to the default JSON output

• ${values}

  • Used in cases where the output is an array of values versus a single object. Like ${value} this by default evaluates to the default JSON output

• ${value.attribute_name}

  • Index into a model to get the value for attribute_name. For example, a model with a cycleCount attribute would be referenced as ${value.cycleCount}

• ${value.name}

  • Returns the name of the model instance or alias

• ${value.quality}

  • Returns the quality as a string, either Good or Bad

• ${value.time}

  • Returns the timestamp as an epoch (UTC)

• ${value.type}

  • Returns the model name

• ${value.elements}

  • Returns a list of key value pairs, where key is the attribute name and value is the attribute value

• ${value.array}

  • Returns an array required by FreeMarker array operations

• ${value.rawString}

  • For use with file typed values to access the raw string data contained in the file

Note: The syntax can be chained together. So if the model has a child model called “motor” with an attribute “amps”, you can access amps using ${value.motor.amps}.

Examples

With this API, here are some example use cases. Please see the FreeMarker documentation online for FreeMarker specific syntax.

Decorate payload (add around payload)

{
	"index": "myindex",
	"source": "mysource",
	"payload": [
		<#list values as value>
		${value}<#if value_has_next>,</#if>
		</#list>
	]
}

Rename a field

{

	"payload": [

	<#list values as value>

		${value?replace("_name", "name")?replace("_model","model")?replace("_timestamp", "timestamp")}
		<#ifvalue_has_next>,</#if>

	</#list>

	]

}

Xml

<root>
	<values>
		<#list values as value>
			<value>
				<#list value.elements as name, v>
					<#if name != "motor">
						<${name}>${v.string}</${name}>
					</#if>
				</#list>
				<motor>
					<#list value.motor.elements as name, v>
						<${name}>${v.string}</${name}>
					</#list>
				</motor>
			</value>
		</#list>
	</values>
</root>

Values in OPC format

{
	"timestamp": ${.now?long},
	"values": [
		<#list values as value>
		{
		"id": "${value.name}",
		"v": ${value},
		"q": ${value.quality},
		"t": ${value.time}
		}<#if value_has_next>,</#if>
		</#list>
	]
}

Values in influxdb format

${value.type},name=${value.name} <#list value.elements as name,v>${name}=${v}<#if name_has_next>,</#if></#list> ${value.time}

Transform time

{
	"values": [
		<#list values as value>
		{
		"id": "${value.name}",
		"v": ${value},
		"q": ${value.quality},
		"t": "${value.time?number_to_datetime?iso_utc}"
		}<#if value_has_next>,</#if>
		</#list>
	]
}