引发 Http404

本课属于 Coddy Django 学习旅程的“Django 基础”单元。第 9 课，共 23 课。

打开 /drinks/mocha/。路由匹配成功，但 DRINKS["mocha"] 会引发 KeyError，网站返回状态码 500，也就是服务器错误。对访问者来说，你的网站看起来像是坏了。

正确的响应是 404，表示页面不存在。视图通过引发 Http404 来说明这一点。这家咖啡馆有 12 张桌子，所以 table 视图可以拒绝 /table/40/：

from django.http import Http404, HttpResponse


def table(request, number):
    if number > 12:
        raise Http404(f"There is no table {number}")
    ...

用 raise，而不是 return：Http404 是一个异常，Django 会将它转换成常见的 404 页面。返回 HttpResponse("No such page") 会显示这些文字，但状态码是 200，这会告诉浏览器和搜索引擎该页面存在。

挑战

简单

在 menu/views.py 中，让 drink 视图在 slug 不在 DRINKS 中时引发 Http404。

打开 /drinks/mocha/ 查看 404 错误消息，然后打开 /drinks/latte/：它仍然可以正常使用。

亲手试试

from django.http import HttpResponse

DRINKS = {
    "espresso": {"name": "Espresso", "price": 2.5, "description": "A short, strong shot of coffee."},
    "latte": {"name": "Latte", "price": 3.5, "description": "Espresso with lots of steamed milk."},
    "flat-white": {"name": "Flat White", "price": 3.75, "description": "Espresso with a thin layer of silky milk."},
    "hot-chocolate": {"name": "Hot Chocolate", "price": 3, "description": "Dark chocolate melted into warm milk."},
}


def home(request):
    return HttpResponse("<h1>Welcome to Corner Café</h1><p>Fresh coffee and cake every day.</p>")


def about(request):
    return HttpResponse("Corner Café opened in 2026.")


def hours(request):
    return HttpResponse("Open every day from 8:00 to 18:00.")


def contact(request):
    return HttpResponse("Write to us at hello@cornercafe.example.")


def table(request, number):
    return HttpResponse(f"<h1>Table {number}</h1>")


def drink(request, slug):
    item = DRINKS[slug]
    return HttpResponse(f"<h1>{item['name']}</h1><p>{item['description']}</p>")


def order(request):
    size = request.GET.get("size", "medium")
    if size not in ["small", "medium", "large"]:
        size = "medium"
    return HttpResponse(f"You ordered a {size} coffee.")