exprTransform component: Expression transformer. Use the expression language provided by the expr (opens new window) library to transform or create new messages.

Configuration

Field	Type	Description	Default
expr	string	Transformation expression, the transformation result replaces msg and goes to the next node	None
mapping	map	Multiple field transformation expressions, format (field:transformation expression)	None

If the mapping field is set, multiple transformation results are converted to json strings and go to the next node. If expr is set, expr is preferred.

• Access the message ID through the ${id} variable.
• Access the message timestamp through the ${ts} variable.
• Access the original content of the message through the ${data} variable.
• Access the message body through the ${msg} variable. If the message's dataType is JSON, you can access the fields of ${msg} by ${msg.XX}. For example: ${msg.temperature} > 50;
• Access the message metadata through the ${metadata} variable. For example ${metadata.customerName}
• Access the message type through the ${msgType} variable.
• Access the data type through the ${dataType} variable.

Expression Examples:

• upper(${msg.name})
• ${metadata.productType}
• ${msg.temperature}+50
• replace(${metadata.productType},'oldValue','newValue')

  For more expr expression syntax, refer to: expr (opens new window)

Relation Type

• Success: Execution successful, send the message to the Success chain
• Failure: Execution failed, send the message to the Failure chain

Execution Result

Replace the msg content with the expression execution result.

Configuration Example

{
  "id": "s2",
  "type": "exprTransform",
  "name": "Expression transformation",
  "configuration": {
    "mapping": {
      "name":        "upper(${msg.name})",
      "tmp":         "${msg.temperature}",
      "alarm":       "${msg.temperature}>50",
      "productType": "${metadata.productType}"
    }
  }
}
}

Related Documentation

• Component Configuration Variables