exprFilter component: Expression filter. Use the expression language provided by the expr (opens new window) library to filter messages.

Configuration

Field	Type	Description	Default
expr	string	Expression, the return value of the expression must be bool type	None

• 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:

• ${msg.temperature} > 50
• ${msg.temperature} > 50 && ${metadata.customerName} == 'rulego'
• upper(${metadata.customerName}[:4]) == 'GO'

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

Relation Type

• True: Send the message to the True chain
• False: Send the message to the False chain
• Failure: Execution failed, send the message to the Failure chain

Execution Result

This component does not change the msg, metadata, and msgType content.

Configuration Example

  {
    "id": "s1",
    "type": "exprFilter",
    "name": "Expression filter",
    "configuration": {
      "expr": "${msg.temperature} > 50"
    }
  }

Related Documentation

• Component Configuration Variables