What is the best way to work with nested JSON structures in Golang?

Question

Id like to work with JSON in Golang, in particular the elastic search JSON protocol.

The JSON is deeply nested (this is a simple query):

{
    "query": {
        "filtered": {
            "query": {
                "match_all": {}
            },
            "filter": {
                "and": [
                    {
                        "range" : {
                            "b" : { 
                                "from" : 4, 
                                "to" : "8"
                            }
                        },
                    },
                    {
                        "term": {
                            "a": "john"
                        }
                    }
                ]
            }
        }
    }
}

This structure maps easily to a native data structure in Ruby.

But with Golang, it seems you have to define the exact structure with structs (perhaps generate them programmatically from the JSON source).

Even so, things like arrays of different "types" of objects in JS requires work arounds and custom code. For example the "and" key in the example JSON. (http://mattyjwilliams.blogspot.co.uk/2013/01/using-go-to-unmarshal-json-lists-with.html).

Is there a better way to work with JSON in Golang?

Answer 1

If you choose to go the struct route, consider this example:

{"data": {"children": [
  {"data": {
    "title": "The Go homepage",
    "url": "http://golang.org/"
  }},
  ...
]}}

// -----------

type Item struct {
    Title string
    URL   string
}

type Response struct {
    Data struct {
        Children []struct {
            Data Item
        }
    }
}

Source: http://talks.golang.org/2012/10things.slide#4

Answer 2

One of the options is to use gabs library: https://github.com/Jeffail/gabs

It's useful for parsing and generating of the complex json structures.

This is the example of the nested json generation from the README:

jsonObj := gabs.New()
// or gabs.Consume(jsonObject) to work on an existing map[string]interface{}

jsonObj.Set(10, "outter", "inner", "value")
jsonObj.SetP(20, "outter.inner.value2")
jsonObj.Set(30, "outter", "inner2", "value3")

Will print:

{"outter":{"inner":{"value":10,"value2":20},"inner2":{"value3":30}}}