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JSLT

  • JSLT is a complete query and transformation language for JSON. The language design is inspired by jq, XPath, and XQuery.

We used custom output processors which are based on JSLT.

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Input message​

A simplified input message could be similar to this:

{
    "DevEUI_uplink": {
        "Time": "2021-12-01T00:00:11.013+01:00",
        "DevEUI": "402C765000000074",
        "FPort": 2,
        "FCntUp": 53,
        "ADRbit": 1,
        "FCntDn": 54,
        "payload_hex": "02300040a0",
        "mic_hex": "61fa24cf",
        "DevAddr": "04D2848E",
        "payload": {
          "temperature": 0.5,
          "batteryVoltage": 3.6
        }
    }
}

JSLT operation​

After receiving a message like the one above, we passed a JSLT operation like this:

{
    "Time": .DevEUI_uplink.Time, 
    "DevEUI": .DevEUI_uplink.DevEUI,
    "FPort": .DevEUI_uplink.FPort,
    "FCntUp": .DevEUI_uplink.FCntUp,
    "FCntDn": .DevEUI_uplink.FCntDn,
    "payload": .DevEUI_uplink.payload_hex,
    "batteryLevel": round(.DevEUI_uplink.payload.batteryVoltage * 100 / 3.6) + "%",
    "temperature": (.DevEUI_uplink.payload.temperature * 9/5) + 32 + " °F",
    "special": "救恩"
}
warning

You can find more information on GIT Schibsted JSLT.

Output message​

The output of the processor is:

{
  "Time": "2021-12-01T00:00:11.013+01:00",
  "DevEUI": "402C765000000074",
  "FPort": 2,
  "FCntUp": 53,
  "FCntDn": 54,
  "payload": "02300040a0",
  "batteryLevel": "100%",
  "temperature": "32.9 °F",
  "special": "救恩"
}