metadataTransform component: metadata transformer. It uses the expression language provided by the expr (opens new window) library to transform metadata or create new metadata.

Configuration

Field	Type	Description	Default Value
mapping	map	Transformation expressions, format (field: transformation expression)	None
isNew	bool	Whether to create a new metadata list, true: create a new metadata list, false: update the corresponding metadata key	false

• 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 type 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: If executed successfully, send the message to the Success chain.
• Failure: If execution fails, send the message to the Failure chain.

Execution Result

Replace the metadata content based on the expression execution result.

Configuration Example

{
  "id": "s1",
  "type": "metadataTransform",
  "name": "Metadata Transformation",
  "configuration": {
    "mapping": {
      "name":        "upper(msg.name)",
      "tmp":         "msg.temperature",
      "alarm":       "msg.temperature>50",
      "productType": "metaData.productType"
    }
  }
}