How to Unmarshall Nested JSON with Unknown Keys and Dynamic Server Names?

Unmarshalling Nested JSON with Unknown Keys

The challenge lies in parsing a JSON structure with an unknown number of outer keys and a confusingly structured nested key. Consider the following JSON format:

{
  "message": {
    "Server1.example.com": [],
    "Server2.example.com": []
  },
  "response_ms": 659,
  "success": true
}

Struct Definition Complications

The complexity stems from the absence of a clear key outside the server name and the dynamic nature of the outer keys. The initial attempt using a deeply nested struct:

type ServerDetails struct {
  Message struct {
    Hostname struct {
      Details struct {
        Application string `json:"application"`
      } `json:"-"`
    } `json:"-"`
  } `json:"message"`
}

fails due to the unknown server names and the single nested key without an outer key.

Dynamic Key Solution

To overcome these challenges, one can utilize a map[string]ServerStruct within the top-level struct. ServerStruct contains application, owner, and other relevant information specific to each server. JSON tags can be strategically added to ensure proper parsing.

Revised Struct Definition

type YourStruct struct {
    Success bool
    ResponseMS int
    Servers map[string]*ServerStruct
}

type ServerStruct struct {
    Application string
    Owner string
    [...]
}

JSON Tags and Unmarshalling

Additional JSON tags are necessary:

{
  "message": {
    "Server1.example.com": [
      {
        "application": "Apache",
        "host": {
          "name": "/^Server-[13456]/"
        },
        "owner": "User1",
        "project": "Web",
        "subowner": "User2"
      }
    ],

The "message" field now unmarshals into a map[string][]ServerStruct. Each key in the map represents a server name, and the corresponding value is an array of ServerStruct. The "host" field is ignored during unmarshalling using the "-" tag.

With these modifications, the JSON data can be successfully parsed into the revised struct.

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