How to Unmarshal Nested JSON with Unknown Keys?

Unraveling Nested JSON with Unknown Keys

Unraveling JSON Complexity

Encountering JSON data with unknown keys and intricate nesting structures can be a daunting task. Consider the following JSON format:

{
  "message": {
    "Server1.example.com": [
      {
        "application": "Apache",
        "host": {
          "name": "/^Server-[13456]/"
        },
        "owner": "User1",
        "project": "Web",
        "subowner": "User2"
      }
    ],
    "Server2.example.com": [
      {
        "application": "Mysql",
        "host": {
          "name": "/^Server[23456]/"
        },
        "owner": "User2",
        "project": "DB",
        "subowner": "User3"
      }
    ]
  },
  "response_ms": 659,
  "success": true
}

As illustrated in this example, server names (Server[0-9].example.com) are not predetermined and can vary. Additionally, the field following server names lacks an explicit key.

Structuring the Solution

To effectively capture this data, we can employ a map[string]ServerStruct structure:

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

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

By incorporating these structures, we enable the allocation of unknown server names into the map.

Unveiling the JSON Secrets

To further excel in unmarshalling the JSON, consider adding necessary JSON tags:

import "encoding/json"

// YourStruct contains the JSON structure with success, response time, and a map of servers
type YourStruct struct {
    Success    bool
    ResponseMS int `json:"response_ms"`
    Servers    map[string]*ServerStruct `json:"message"`
}

// ServerStruct holds server information, including application, owner, etc.
type ServerStruct struct {
    Application string `json:"application"`
    Owner       string `json:"owner"`
    [...]
}

// UnmarshalJSON is a custom unmarshaller that handles nesting and unknown keys
func (s *YourStruct) UnmarshalJSON(data []byte) error {
    type YourStructHelper struct {
        Success    bool
        ResponseMS int               `json:"response_ms"`
        Servers    map[string]ServerStruct `json:"message"`
    }
    var helper YourStructHelper
    if err := json.Unmarshal(data, &helper); err != nil {
        return err
    }
    s.Success = helper.Success
    s.ResponseMS = helper.ResponseMS
    s.Servers = make(map[string]*ServerStruct)
    for k, v := range helper.Servers {
        s.Servers[k] = &v // Explicitly allocate memory for each server
    }
    return nil
}

With these adjustments, you can effectively unmarshal the provided JSON into your custom struct, paving the way for effortless data manipulation.

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