Create handler

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Goal

Add POST /items with input validation. After this page you can create items through the API and read them back with GET /items.

Prerequisites

• List and get handlers — the mux and the Store

What the handler does

POST /items expects a JSON body with a name field. The handler:

1. Decodes the body.
2. Rejects an empty name (a name of only whitespace is treated as empty).
3. Calls store.Create to insert the row.
4. Returns the new item as JSON with status 201 Created.

The handler

Add handleCreate to handlers.go:

package main

import (
	"database/sql"
	"encoding/json"
	"net/http"
	"strconv"
	"strings"
)

func handleCreate(s *Store) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		var in struct{ Name string `json:"name"` }
		if err := json.NewDecoder(r.Body).Decode(&in); err != nil {
			http.Error(w, "bad json", http.StatusBadRequest)
			return
		}
		if strings.TrimSpace(in.Name) == "" {
			http.Error(w, "name required", http.StatusBadRequest)
			return
		}
		it, err := s.Create(in.Name)
		if err != nil {
			http.Error(w, "internal error", http.StatusInternalServerError)
			return
		}
		w.Header().Set("Content-Type", "application/json")
		w.WriteHeader(http.StatusCreated)
		json.NewEncoder(w).Encode(it)
	}
}

w.WriteHeader(http.StatusCreated) must come after setting headers and before writing the body. Calling WriteHeader sends the status line and all headers set so far — anything you add after that is ignored.

Wiring

Add the route to main.go:

mux.Handle("POST /items", handleCreate(store))

Your full mux block now looks like:

mux := http.NewServeMux()
mux.Handle("GET /items", handleList(store))
mux.Handle("GET /items/{id}", handleGet(store))
mux.Handle("POST /items", handleCreate(store))

Checkpoint

go run .

In a second terminal, create an item:

curl -s -X POST http://localhost:8080/items \
  -H "Content-Type: application/json" \
  -d '{"name":"pen"}'

Expected (status 201):

{"id":1,"name":"pen"}

List all items:

curl http://localhost:8080/items

Expected:

[{"id":1,"name":"pen"}]

Test validation — send an empty name:

curl -s -o /dev/null -w "%{http_code}" -X POST http://localhost:8080/items \
  -H "Content-Type: application/json" \
  -d '{"name":""}'

Expected: 400

Stop the server with Ctrl-C.

Next → 07 Config