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luaTransform

luaTransform Component: Lua Script Transformer. It can transform or enhance msg, metadata, msgType, and dataType using Lua scripts. The transformed message is then passed to the next node. It can also load third-party Lua libraries to perform advanced operations such as encryption/decryption, I/O, networking, and file handling.

To enable advanced operations such as encryption/decryption, I/O, networking, and file handling in Lua scripts, the following configuration is required: config.Properties.PutValue(luaEngine.LoadLuaLibs, "true")

Lua scripts support Lua 5.1 syntax. For more details, refer to gopher-lua (opens new window).

# Configuration

Field Type Description Default Value
script string Lua script or file path of a Lua script with a .lua suffix None

  • script: This can transform msg, metadata, and msgType. Only the function body content is required. If it is a file path, a complete script function must be provided:

        function Transform(msg, metadata, msgType, dataType) 
        ${script} 
     end
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    • msg: Message content. If dataType=JSON, it can be accessed and modified using msg.temperature. If dataType is of another type, the field type is string.
    • metadata: Message metadata, type: jsonObject.
    • msgType: Message type.
    • dataType: Message data type (JSON, TEXT, BINARY, etc.), which needs to be used as a string in Lua.
    • Return value type: msg, metadata, msgType

Data Type Handling

  • JSON Type: The msg parameter is a Lua table, and fields can be accessed and modified directly, such as msg.temperature = 30.
  • BINARY Type: The msg parameter is a Lua table (byte array), and the first byte can be accessed using msg[1] (1-based index). A new byte array can be returned.
  • Other Types: The msg parameter is a string.
  • Returning Binary Data: Return a Lua table containing numbers (0-255), such as {0xAA, 0xBB, 0x01, 0x02}.

# Relation Type

  • True: Send the message to the True chain.
  • False: Send the message to the False chain.
  • Failure: In case of execution failure, send the message to the Failure chain.

# Execution Result

The script modifies the content of msg, metadata, and msgType.

# Configuration Examples

# Basic Transformation Example

  {
    "id": "s1",
    "type": "x/luaTransform",
    "name": "Transformation",
    "configuration": {
      "script": " 	-- Convert temperature from Celsius to Fahrenheit 
      msg.temperature = msg.temperature * 1.8 + 32
      -- Add a field to metadata to indicate the temperature unit
      metadata.unit = \"F\"
      metadata.from = global.from
      metadata.add = add(5,4)
      return msg, metadata, msgType"
      
    }
  }
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# Data Type Handling Example

  {
    "id": "s2",
    "type": "x/luaTransform",
    "name": "Smart Transformation",
    "configuration": {
      "script": "metadata.originalType = dataType; if dataType == 'JSON' then msg.processed = true; msg.timestamp = os.date('%Y-%m-%d %H:%M:%S') elseif dataType == 'BINARY' then metadata.binaryLength = #msg elseif dataType == 'TEXT' then metadata.textLength = string.len(msg) end; return msg, metadata, msgType"
    }
  }
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# Adding a Binary Header Example

  {
    "id": "s3",
    "type": "x/luaTransform",
    "name": "Add Binary Header",
    "configuration": {
      "script": "if dataType == 'BINARY' then local result = {0xAA, 0xBB}; for i = 1, #msg do table.insert(result, msg[i]) end; metadata.headerAdded = 'true'; return result, metadata, msgType end; return msg, metadata, msgType"
    }
  }
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# Binary Data Encryption Example

  {
    "id": "s4", 
    "type": "x/luaTransform",
    "name": "XOR Encryption",
    "configuration": {
      "script": "if dataType == 'BINARY' then local result = {}; for i = 1, #msg do table.insert(result, msg[i] ~ 0x55) end; metadata.encrypted = 'true'; metadata.algorithm = 'xor'; return result, metadata, msgType end; return msg, metadata, msgType"
    }
  }
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# Device Protocol Parsing Example

  {
    "id": "s5",
    "type": "x/luaTransform",
    "name": "Protocol Parsing",
    "configuration": {
      "script": "if dataType == 'BINARY' and #msg >= 6 then local deviceId = msg[1] * 256 + msg[2]; local functionCode = msg[3] * 256 + msg[4]; local dataLength = msg[5] * 256 + msg[6]; local payload = {}; for i = 7, #msg do table.insert(payload, msg[i]) end; local result = {deviceId = deviceId, functionCode = functionCode, dataLength = dataLength, payload = payload, parsedAt = os.date('%Y-%m-%d %H:%M:%S')}; metadata.protocol = 'custom'; metadata.parsed = 'true'; return result, metadata, 'PARSED_DATA' end; return msg, metadata, msgType"
    }
  }
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# Text Log Parsing Example

  {
    "id": "s6",
    "type": "x/luaTransform", 
    "name": "Log Parsing",
    "configuration": {
      "script": "if dataType == 'TEXT' then local pattern = '(%d%d%d%d%-%d%d%-%d%d %d%d:%d%d:%d%d) %[([%w]+)%] (.+)'; local timestamp, level, message = string.match(msg, pattern); if timestamp then local result = {timestamp = timestamp, level = level, message = message, source = 'application'}; metadata.logParsed = 'true'; return result, metadata, 'LOG_ENTRY' end end; return msg, metadata, msgType"
    }
  }
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# Custom Functions

You can register golang functions with config.RegisterUdf and use them in Lua scripts. The registration method and usage are the same as Js. For details, refer to Udf.

# Loading Lua Modules

You can extend Lua capabilities by loading Lua custom or third-party module libraries. Use the following method to register Lua modules to the engine:

import luaEngine "github.com/rulego/rulego-components/pkg/lua_engine"

luaEngine.Preloader.Register(func(state *lua.LState) {
	//load module
	//libs.Preload(state)
})
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Creating a module by Go (opens new window)

In addition, the framework has built-in a large number of Lua third-party library modules. Use the following method to enable them, which are not loaded by default:

config.Properties.PutValue(luaEngine.LoadLuaLibs, "true")
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After starting, you can perform advanced operations such as encryption/decryption, I/O, network, database, file, etc. The list of third-party libraries is:

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Last Updated: 2025/06/23, 10:45:49
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