go 32 lines · 5 steps

How Gin renders MsgPack responses

A custom Render implementation serializes any value to MessagePack and wires it into Gin's response pipeline.

Explained by highlit
Gin Intermediate serialization content-type interface-implementation encoding
1package render
2 
3import (
4 "net/http"
5 
6 "github.com/vmihailenco/msgpack/v5"
7)
8 
9var msgpackContentType = []string{"application/msgpack; charset=utf-8"}
10 
11type MsgPack struct {
12 Data any
13}
14 
15func (r MsgPack) Render(w http.ResponseWriter) error {
16 r.WriteContentType(w)
17 
18 enc := msgpack.NewEncoder(w)
19 enc.SetCustomStructTag("json")
20 return enc.Encode(r.Data)
21}
22 
23func (r MsgPack) WriteContentType(w http.ResponseWriter) {
24 header := w.Header()
25 if val := header["Content-Type"]; len(val) == 0 {
26 header["Content-Type"] = msgpackContentType
27 }
28}
29 
30func MsgPackResponse(c *gin.Context, code int, obj any) {
31 c.Render(code, MsgPack{Data: obj})
32}
01 / 01
STEP 01

Walkthrough

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Three takeaways
  1. 1Implementing Gin's Render interface lets you plug any serialization format into the framework's response machinery.
  2. 2Setting the Content-Type only when unset lets callers override the header without being clobbered.
  3. 3Reusing the JSON struct tags for MessagePack keeps one set of field annotations across formats.

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