I am trying to parse and get selected data from a deep nested json data in Go Lang. I'm having issues navigating through the structure and accessing the data. The data is too deep and complex to be parsed with a-priori known structures in Go. Here is the URL of the file: -https://www.data.gouv.fr/api/1/datasets/?format=csv&page=0&page_size=20
I did some parsing with map interfaces and using a json string:
resultdata := map[string]interface {}
json.Unmarshal([]byte(inputbytestring), &resultdata) //Inputstring is the string containing the JSON data of the above URL
The problem:
Once you have data as a map[string]interface{}, you can use type assertions to get to the lower levels of data.
There's a good explanation here of how to do this at https://blog.golang.org/json-and-go
Here's an example to get you most of the way:
https://play.golang.org/p/P8cGP1mTDmD
package main
import (
"encoding/json"
"fmt"
"log"
)
func main() {
jsonData := `{
"string": "string_value",
"number": 123.45,
"js_array": ["a", "b", "c"],
"integer": 678,
"subtype": {
"number_array": [1, 2, 3]
}
}`
m := map[string]interface{}{}
err := json.Unmarshal([]byte(jsonData), &m)
if err != nil {
log.Fatal(err)
}
for key, value := range m {
switch v := value.(type) {
case int:
fmt.Printf("Key: %s, Integer: %d
", key, v)
case float64:
fmt.Printf("Key: %s, Float: %v
", key, v)
case string:
fmt.Printf("Key: %s, String: %s
", key, v)
case map[string]interface{}:
fmt.Printf("Key: %s, Subtype: %+v
", key, v)
case []interface{}:
//TODO: Read through each item in the interface and work out what type it is.
fmt.Printf("Key: %s, []interface: %v
", key, v)
default:
fmt.Printf("Key: %s, unhandled type: %+v
", key, v)
}
}
}
Alternatively https://mholt.github.io/json-to-go/ does a decent job of turning examples of JSON data into Go structs that can be used for marshalling.
Putting the example in, I get something that isn't too bad.
type AutoGenerated struct {
Data []struct {
Acronym interface{} `json:"acronym"`
Badges []interface{} `json:"badges"`
CreatedAt string `json:"created_at"`
Deleted interface{} `json:"deleted"`
Description string `json:"description"`
Extras struct {
} `json:"extras"`
Frequency string `json:"frequency"`
FrequencyDate interface{} `json:"frequency_date"`
ID string `json:"id"`
LastModified string `json:"last_modified"`
LastUpdate string `json:"last_update"`
License string `json:"license"`
Metrics struct {
Discussions int `json:"discussions"`
Followers int `json:"followers"`
Issues int `json:"issues"`
NbHits int `json:"nb_hits"`
NbUniqVisitors int `json:"nb_uniq_visitors"`
NbVisits int `json:"nb_visits"`
Reuses int `json:"reuses"`
Views int `json:"views"`
} `json:"metrics"`
Organization struct {
Acronym string `json:"acronym"`
Class string `json:"class"`
ID string `json:"id"`
Logo string `json:"logo"`
LogoThumbnail string `json:"logo_thumbnail"`
Name string `json:"name"`
Page string `json:"page"`
Slug string `json:"slug"`
URI string `json:"uri"`
} `json:"organization"`
Owner interface{} `json:"owner"`
Page string `json:"page"`
Private bool `json:"private"`
Resources []struct {
Checksum struct {
Type string `json:"type"`
Value string `json:"value"`
} `json:"checksum"`
CreatedAt string `json:"created_at"`
Description interface{} `json:"description"`
Extras struct {
} `json:"extras"`
Filesize int `json:"filesize"`
Filetype string `json:"filetype"`
Format string `json:"format"`
ID string `json:"id"`
LastModified string `json:"last_modified"`
Latest string `json:"latest"`
Metrics struct {
NbHits int `json:"nb_hits"`
NbUniqVisitors int `json:"nb_uniq_visitors"`
NbVisits int `json:"nb_visits"`
Views int `json:"views"`
} `json:"metrics"`
Mime string `json:"mime"`
PreviewURL string `json:"preview_url"`
Published string `json:"published"`
Title string `json:"title"`
Type string `json:"type"`
URL string `json:"url"`
} `json:"resources"`
Slug string `json:"slug"`
Spatial interface{} `json:"spatial"`
Tags []interface{} `json:"tags"`
TemporalCoverage interface{} `json:"temporal_coverage"`
Title string `json:"title"`
URI string `json:"uri"`
} `json:"data"`
Facets struct {
Format [][]interface{} `json:"format"`
} `json:"facets"`
NextPage string `json:"next_page"`
Page int `json:"page"`
PageSize int `json:"page_size"`
PreviousPage interface{} `json:"previous_page"`
Total int `json:"total"`
}