go 56 lines · 7 steps

Parsing search query params in a Go handler

An HTTP handler that safely reads, validates, and defaults query parameters before running a search.

Explained by highlit
Intermediate http-handlers input-validation defaults query-parsing json-response
1package handlers
2 
3import (
4 "encoding/json"
5 "net/http"
6 "strconv"
7 "strings"
8)
9 
10type searchParams struct {
11 Query string
12 Tags []string
13 Page int
14 PerPage int
15 SortDesc bool
16}
17 
18func SearchHandler(w http.ResponseWriter, r *http.Request) {
19 if err := r.ParseForm(); err != nil {
20 http.Error(w, "invalid form encoding", http.StatusBadRequest)
21 return
22 }
23 
24 p := searchParams{
25 Query: strings.TrimSpace(r.FormValue("q")),
26 Page: 1,
27 PerPage: 25,
28 SortDesc: r.FormValue("order") == "desc",
29 }
30 
31 for _, tag := range r.Form["tag"] {
32 if tag = strings.TrimSpace(tag); tag != "" {
33 p.Tags = append(p.Tags, tag)
34 }
35 }
36 
37 if page, err := strconv.Atoi(r.FormValue("page")); err == nil && page > 0 {
38 p.Page = page
39 }
40 if per, err := strconv.Atoi(r.FormValue("per_page")); err == nil && per > 0 && per <= 100 {
41 p.PerPage = per
42 }
43 
44 results, total, err := searchArticles(r.Context(), p)
45 if err != nil {
46 http.Error(w, "search failed", http.StatusInternalServerError)
47 return
48 }
49 
50 w.Header().Set("Content-Type", "application/json")
51 json.NewEncoder(w).Encode(map[string]any{
52 "results": results,
53 "total": total,
54 "page": p.Page,
55 })
56}
01 / 01
STEP 01

Walkthrough

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Three takeaways
  1. 1Start from sensible defaults and only overwrite them when incoming input parses and passes bounds checks.
  2. 2Validating page and per-page limits at the edge protects downstream queries from abusive or malformed input.
  3. 3Guarding each failure with an early return keeps the happy path flat and readable.

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