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.

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

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": [
      {
      }
    ]
  }
}