Component Configuration Variables

In certain scenarios, it’s necessary to uniformly modify component configurations or dynamically replace them during component runtime. You can achieve this by using built-in variables to substitute component configurations. The syntax is as follows: ${key} or ${key.subKey}.

Global Variables

Global variables are executed for replacement logic during component initialization (when the component's Init method is executed), including the following variables:

• global variable: Access values from config.Properties, for example, ${global.key}.
• vars variable: Access values from rule chain vars, for example, ${vars.key}.

Global Variables: All component configuration fields support variable substitution.

Runtime Variables

Runtime Variables are executed for replacement logic during component runtime (when the component's OnMsg method is executed), including the following variables:

• id variable: Access the message ID.
• ts variable: Access the message timestamp.
• data variable: Access the original message content.
• msg variable: Access the transformed message data. If the message's dataType is JSON, you can access fields using ${msg.key}.
• metadata variable: Access message metadata, e.g., ${metadata.key}.
• type variable: Access the message type.
• dataType variable: Access the data type.
• nodeId variable: v0.33.0+ Cross-node variable for accessing output data from specified nodes. Examples: ${node1.msg.temperature}, ${node1.metadata.deviceId}, ${node1.type}, etc.

Runtime Variables: Only specific component configuration fields, as indicated, support variable substitution.

Cross-Node Variables Details

Cross-node variables allow accessing output data from any previously executed node in the rule chain within component configurations. The syntax format is: ${nodeId.field}

Supported fields include:

• ${nodeId.msg}: Access the message content of the specified node
• ${nodeId.msg.fieldName}: Access specific fields in the specified node's message (when message is in JSON format)
• ${nodeId.metadata}: Access the metadata of the specified node
• ${nodeId.metadata.key}: Access specific key-value pairs in the specified node's metadata
• ${nodeId.type}: Access the message type of the specified node
• ${nodeId.dataType}: Access the data type of the specified node
• ${nodeId.id}: Access the message ID of the specified node
• ${nodeId.ts}: Access the message timestamp of the specified node

Note: Cross-node variables require the target node to have completed execution and produced output. During rule chain initialization, if cross-node variables in the format ${nodeId.xx.xx} are detected in component configurations, corresponding dependency relationships will be automatically established to ensure data availability.

Examples

Basic Variables Example

{
  "ruleChain": {
	"id":"rule01",
    "name": "test",
    "configuration": {
      "vars": {
        "topicPrefix":"/device/msg"
      }
    }
  },
  "metadata": {
    "nodes": [
      {
        "id": "s2",
        "type": "mqttClient",
        "name": "push data",
        "configuration": {
          "server": "${global.mqttServer}",
          "topic": "${vars.topicPrefix}/${metadata.deviceId}"
        }
      }
    ],
    "connections": [
      {
      }
    ]
  }
}

Cross-Node Variables Example

{
  "ruleChain": {
    "id": "rule02",
    "name": "cross-node-example"
  },
  "metadata": {
    "nodes": [
      {
        "id": "sensor1",
        "type": "jsTransform",
        "name": "Sensor Data Processing",
        "configuration": {
          "jsScript": "msg.temperature = 25.5; msg.humidity = 60; return {msg: msg, metadata: metadata, msgType: msgType};"
        }
      },
      {
        "id": "sensor2",
        "type": "jsTransform",
        "name": "Another Sensor",
        "configuration": {
          "jsScript": "msg.pressure = 1013.25; return {msg: msg, metadata: metadata, msgType: msgType};"
        }
      },
      {
        "id": "combiner",
        "type": "jsTransform",
        "name": "Data Combiner",
        "configuration": {
          "jsScript": "var combined = {temperature: ${sensor1.msg.temperature}, humidity: ${sensor1.msg.humidity}, pressure: ${sensor2.msg.pressure}, timestamp: ${sensor1.ts}}; return {msg: combined, metadata: metadata, msgType: msgType};"
        }
      },
      {
        "id": "logger",
        "type": "log",
        "name": "Logger",
        "configuration": {
          "jsScript": "return 'Combined data - Temp: ${sensor1.msg.temperature}°C, Humidity: ${sensor1.msg.humidity}%, Pressure: ${sensor2.msg.pressure}hPa';"
        }
      }
    ],
    "connections": [
      {
        "fromId": "sensor1",
        "toId": "combiner",
        "type": "Success"
      },
      {
        "fromId": "sensor2",
        "toId": "combiner",
        "type": "Success"
      },
      {
        "fromId": "combiner",
        "toId": "logger",
        "type": "Success"
      }
    ]
  }
}