如何在Golang中将jsonb编码为http响应的一部分

Question

I'm having a tough time moving json over the wire.

There is a jsonb field in a Postgres db that I need to add to a struct before sending it over the wire as an http response.

If the struct's payload field is a string, marshaling escapes the json like "{\"id\": \"3aa5fff0-ad91-41b1-84f0-d97f38e0e0f4\", \"user\": 1 }.

If the struct's payload field is a json.RawMessage, marshalling escapes the json as (what I imagine to be) a sequence of base64 encoded bytes.

This is the struct that I am marshaling and writing to the http response stream:

type NestJobReturn struct { Status string `json:"status"` Nest json.RawMessage `json:"nest"` }

I build a ret instance of this struct and print it out. If I use %v it shows bytes, and %s shows it as the proper, un-escaped json string:

log("Value of ret.Nest: %v", ret.Nest) // Value of ret.Nest: [123 34 105 ... log("Value of ret.Nest as a string: %s", ret.Nest) // Value of ret.Nest as a string: {"id": "f053...

Marshaling and i/o is done thusly:

js, _ := json.Marshal(ret) res.Header().Set("Content-Type", "application/json") res.Write(js)

The client currently receives the entire message looking kinda like this:

{"status":"ok","nest":"eyJpZCI6ICJmMD..."}

... but the intended value of "nest" is the valid json from my jsonb column in the database.

Any ideas?

Answer 1

You need to define the nested field as a pointer to json.RawMessage, e.g.

type NestJobReturn struct {
    Status string           `json:"status"`
    Nest   *json.RawMessage `json:"nest"`
}

jsonStr := `{"type": "Object", "desc": "Simple nested object"}`
raw := json.RawMessage(jsonStr)

ret := NestJobReturn {
    Status: "DONE",
    Nest:   &raw,
}

A working example https://play.golang.org/p/Ju7kgbawss