go 35 lines · 4 steps

Content negotiation in Gin handlers

A single Gin handler serves the same product as JSON or XML by honoring the client's Accept header.

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Gin Intermediate content-negotiation struct-tags rest-api serialization http
1package handlers
2 
3import (
4 "net/http"
5 
6 "github.com/gin-gonic/gin"
7)
8 
9type Product struct {
10 XMLName struct{} `json:"-" xml:"product"`
11 ID int `json:"id" xml:"id"`
12 Name string `json:"name" xml:"name"`
13 Price float64 `json:"price" xml:"price"`
14 Tags []string `json:"tags" xml:"tags>tag"`
15}
16 
17func GetProduct(c *gin.Context) {
18 id := c.Param("id")
19 
20 product, err := productStore.FindByID(c.Request.Context(), id)
21 if err != nil {
22 c.Negotiate(http.StatusNotFound, gin.Negotiate{
23 Offered: []string{gin.MIMEJSON, gin.MIMEXML},
24 Data: gin.H{"error": "product not found"},
25 })
26 return
27 }
28 
29 c.Negotiate(http.StatusOK, gin.Negotiate{
30 Offered: []string{gin.MIMEJSON, gin.MIMEXML},
31 Data: product,
32 JSONData: product,
33 XMLData: product,
34 })
35}
01 / 01
STEP 01

Walkthrough

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Three takeaways
  1. 1Content negotiation lets one endpoint respond in multiple formats based on the client's Accept header.
  2. 2Dual struct tags let the same Go type serialize cleanly to both JSON and XML.
  3. 3Offering a consistent format list on both success and error keeps negotiated responses uniform.

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