go_net_http_rest_api_with_json_and_route_patterns.go

1package main
2
3import (
4	"encoding/json"
5	"fmt"
6	"net/http"
7)
8
9// album represents data about a record album.
10type album struct {
11	ID     string  `json:"id"`
12	Title  string  `json:"title"`
13	Artist string  `json:"artist"`
14	Price  float64 `json:"price"`
15}
16
17// albums slice to seed record album data.
18var albums = []album{
19	{ID: "1", Title: "Blue Train", Artist: "John Coltrane", Price: 56.99},
20	{ID: "2", Title: "Jeru", Artist: "Gerry Mulligan", Price: 17.99},
21	{ID: "3", Title: "Sarah Vaughan and Clifford Brown", Artist: "Sarah Vaughan", Price: 39.99},
22}
23
24// getAlbums responds with the list of all albums as JSON.
25func getAlbums(w http.ResponseWriter, r *http.Request) {
26	w.Header().Set("Content-Type", "application/json")
27	json.NewEncoder(w).Encode(albums)
28}
29
30// postAlbums adds an album from JSON received in the request body.
31func postAlbums(w http.ResponseWriter, r *http.Request) {
32	var newAlbum album
33
34	// Call Decode to read the body into newAlbum.
35	if err := json.NewDecoder(r.Body).Decode(&newAlbum); err != nil {
36		http.Error(w, err.Error(), http.StatusBadRequest)
37		return
38	}
39
40	// Add the new album to the slice.
41	albums = append(albums, newAlbum)
42	w.Header().Set("Content-Type", "application/json")
43	w.WriteHeader(http.StatusCreated)
44	json.NewEncoder(w).Encode(newAlbum)
45}
46
47// getAlbumByID locates the album whose ID value matches the id
48// parameter sent by the client, then returns that album as a response.
49func getAlbumByID(w http.ResponseWriter, r *http.Request) {
50	id := r.PathValue("id")
51
52	// Loop over the list of albums, looking for
53	// an album whose ID value matches the parameter.
54	for _, a := range albums {
55		if a.ID == id {
56			w.Header().Set("Content-Type", "application/json")
57			json.NewEncoder(w).Encode(a)
58			return
59		}
60	}
61	http.Error(w, "album not found", http.StatusNotFound)
62}
63
64func main() {
65	mux := http.NewServeMux()
66
67	// Registering routes using the enhanced routing patterns (Go 1.22+)
68	mux.HandleFunc("GET /albums", getAlbums)
69	mux.HandleFunc("GET /albums/{id}", getAlbumByID)
70	mux.HandleFunc("POST /albums", postAlbums)
71
72	fmt.Println("Starting server on :8080...")
73	http.ListenAndServe(":8080", mux)
74}