每天40分玩转Django：Django视图和URL

Django视图和URL

一、课程概述

学习项目	具体内容	预计用时
视图基础	函数视图、类视图、视图装饰器	90分钟
URL配置	URL模式、路由系统、命名URL	60分钟
请求处理	请求对象、响应对象、中间件	90分钟

二、视图基础

2.1 函数视图

# blog/views.py
from django.shortcuts import render, get_object_or_404, redirect
from django.http import HttpResponse
from .models import Post, Category
from .forms import PostForm

# 简单的函数视图
def hello_world(request):
    return HttpResponse("Hello, Django!")

# 带模板渲染的视图
def post_list(request):
    posts = Post.objects.all().order_by('-publish')
    return render(request, 'blog/post_list.html', {'posts': posts})

# 处理表单的视图
def post_create(request):
    if request.method == 'POST':
        form = PostForm(request.POST)
        if form.is_valid():
            post = form.save(commit=False)
            post.author = request.user
            post.save()
            return redirect('blog:post_detail', post.id)
    else:
        form = PostForm()
    return render(request, 'blog/post_form.html', {'form': form})

# 详情视图
def post_detail(request, post_id):
    post = get_object_or_404(Post, id=post_id)
    return render(request, 'blog/post_detail.html', {'post': post})

2.2 类视图

# blog/views.py
from django.views.generic import ListView, DetailView, CreateView, UpdateView, DeleteView
from django.urls import reverse_lazy
from django.contrib.auth.mixins import LoginRequiredMixin

# 列表视图
class PostListView(ListView):
    model = Post
    template_name = 'blog/post_list.html'
    context_object_name = 'posts'
    paginate_by = 10
    ordering = ['-publish']

    def get_queryset(self):
        queryset = super().get_queryset()
        category_id = self.request.GET.get('category')
        if category_id:
            queryset = queryset.filter(category_id=category_id)
        return queryset

# 详情视图
class PostDetailView(DetailView):
    model = Post
    template_name = 'blog/post_detail.html'
    context_object_name = 'post'

# 创建视图
class PostCreateView(LoginRequiredMixin, CreateView):
    model = Post
    template_name = 'blog/post_form.html'
    fields = ['title', 'body', 'category', 'status']
    success_url = reverse_lazy('blog:post_list')

    def form_valid(self, form):
        form.instance.author = self.request.user
        return super().form_valid(form)

# 更新视图
class PostUpdateView(LoginRequiredMixin, UpdateView):
    model = Post
    template_name = 'blog/post_form.html'
    fields = ['title', 'body', 'category', 'status']

    def get_success_url(self):
        return reverse_lazy('blog:post_detail', kwargs={'pk': self.object.pk})

# 删除视图
class PostDeleteView(LoginRequiredMixin, DeleteView):
    model = Post
    success_url = reverse_lazy('blog:post_list')
    template_name = 'blog/post_confirm_delete.html'

2.3 视图装饰器

# blog/views.py
from django.contrib.auth.decorators import login_required, permission_required
from django.views.decorators.http import require_http_methods
from django.views.decorators.cache import cache_page

# 登录要求装饰器
@login_required
def profile(request):
    return render(request, 'blog/profile.html', {'user': request.user})

# HTTP方法限制装饰器
@require_http_methods(["GET", "POST"])
def post_edit(request, post_id):
    post = get_object_or_404(Post, id=post_id)
    if request.method == 'POST':
        # 处理POST请求
        pass
    return render(request, 'blog/post_edit.html', {'post': post})

# 缓存装饰器
@cache_page(60 * 15)  # 缓存15分钟
def category_list(request):
    categories = Category.objects.all()
    return render(request, 'blog/category_list.html', {'categories': categories})

三、URL配置

3.1 URL模式

# blog/urls.py
from django.urls import path
from . import views

app_name = 'blog'

urlpatterns = [
    # 函数视图URL
    path('', views.post_list, name='post_list'),
    path('post/<int:post_id>/', views.post_detail, name='post_detail'),
    path('post/new/', views.post_create, name='post_create'),
    
    # 类视图URL
    path('posts/', views.PostListView.as_view(), name='posts'),
    path('post/<int:pk>/detail/', views.PostDetailView.as_view(), name='post_detail'),
    path('post/add/', views.PostCreateView.as_view(), name='post_add'),
    path('post/<int:pk>/edit/', views.PostUpdateView.as_view(), name='post_edit'),
    path('post/<int:pk>/delete/', views.PostDeleteView.as_view(), name='post_delete'),
    
    # 带参数的URL
    path('category/<slug:category_slug>/', views.category_posts, name='category_posts'),
    path('tag/<slug:tag_slug>/', views.tag_posts, name='tag_posts'),
    path('archive/<int:year>/<int:month>/', views.archive_posts, name='archive_posts'),
]

3.2 高级URL配置

# myproject/urls.py
from django.contrib import admin
from django.urls import path, include
from django.conf import settings
from django.conf.urls.static import static

urlpatterns = [
    path('admin/', admin.site.urls),
    path('blog/', include('blog.urls', namespace='blog')),
    path('api/', include('blog.api.urls')),  # API URLs
    path('accounts/', include('django.contrib.auth.urls')),
] + static(settings.MEDIA_URL, document_root=settings.MEDIA_ROOT)

# 自定义错误页面
handler404 = 'myproject.views.custom_404'
handler500 = 'myproject.views.custom_500'

四、请求和响应处理

4.1 请求对象

# blog/views.py
def process_request(request):
    # 获取GET参数
    page = request.GET.get('page', 1)
    category = request.GET.get('category')
    
    # 获取POST数据
    if request.method == 'POST':
        title = request.POST.get('title')
        content = request.POST.get('content')
        
    # 获取文件
    if request.FILES:
        image = request.FILES['image']
        
    # 获取cookies
    user_id = request.COOKIES.get('user_id')
    
    # 获取session数据
    cart = request.session.get('cart', {})
    
    # 获取用户信息
    if request.user.is_authenticated:
        username = request.user.username

4.2 响应对象

# blog/views.py
from django.http import JsonResponse, FileResponse, StreamingHttpResponse
from django.shortcuts import render, redirect

def multiple_responses(request):
    # HTML响应
    return render(request, 'template.html', context)
    
    # 重定向
    return redirect('blog:post_list')
    
    # JSON响应
    data = {'status': 'success', 'message': 'Data received'}
    return JsonResponse(data)
    
    # 文件下载
    file_path = 'path/to/file.pdf'
    return FileResponse(open(file_path, 'rb'))
    
    # 流式响应
    def file_iterator(file_path, chunk_size=8192):
        with open(file_path, 'rb') as f:
            while True:
                chunk = f.read(chunk_size)
                if not chunk:
                    break
                yield chunk
                
    return StreamingHttpResponse(file_iterator(file_path))

4.3 中间件

# blog/middleware.py
import time
from django.utils.deprecation import MiddlewareMixin

class RequestTimingMiddleware(MiddlewareMixin):
    def process_request(self, request):
        request.start_time = time.time()

    def process_response(self, request, response):
        if hasattr(request, 'start_time'):
            duration = time.time() - request.start_time
            response['X-Request-Duration'] = str(duration)
        return response

# settings.py
MIDDLEWARE = [
    'django.middleware.security.SecurityMiddleware',
    'django.contrib.sessions.middleware.SessionMiddleware',
    'django.middleware.common.CommonMiddleware',
    'django.middleware.csrf.CsrfViewMiddleware',
    'django.contrib.auth.middleware.AuthenticationMiddleware',
    'django.contrib.messages.middleware.MessageMiddleware',
    'django.middleware.clickjacking.XFrameOptionsMiddleware',
    'blog.middleware.RequestTimingMiddleware',  # 自定义中间件
]

五、实战示例：博客搜索功能

# blog/views.py
from django.db.models import Q

def post_search(request):
    query = request.GET.get('q', '')
    results = []
    
    if query:
        results = Post.objects.filter(
            Q(title__icontains=query) |
            Q(body__icontains=query) |
            Q(tags__name__icontains=query)
        ).distinct()
        
    return render(request,
                 'blog/search.html',
                 {'query': query,
                  'results': results})

# blog/templates/blog/search.html
{% extends "blog/base.html" %}

{% block content %}
    <h2>搜索结果</h2>
    <form method="get">
        <input type="text" name="q" value="{{ query }}" placeholder="搜索文章...">
        <button type="submit">搜索</button>
    </form>

    {% if query %}
        <h3>包含 "{{ query }}" 的文章：</h3>
        {% if results %}
            {% for post in results %}
                <article>
                    <h4><a href="{% url 'blog:post_detail' post.id %}">{{ post.title }}</a></h4>
                    <p>{{ post.body|truncatewords:30 }}</p>
                </article>
            {% endfor %}
        {% else %}
            <p>没有找到相关文章。</p>
        {% endif %}
    {% endif %}
{% endblock %}

六、常见问题和解决方案

1. 处理404错误：

# views.py
from django.http import Http404

def post_detail(request, post_id):
    try:
        post = Post.objects.get(id=post_id)
    except Post.DoesNotExist:
        raise Http404("Post does not exist")
    return render(request, 'blog/post_detail.html', {'post': post})

2. CSRF验证：

<!-- templates/form.html -->
<form method="post">
    {% csrf_token %}
    {{ form.as_p }}
    <button type="submit">提交</button>
</form>

3. 文件上传处理：

# views.py
def upload_file(request):
    if request.method == 'POST' and request.FILES['file']:
        myfile = request.FILES['file']
        fs = FileSystemStorage()
        filename = fs.save(myfile.name, myfile)
        uploaded_file_url = fs.url(filename)
        return render(request, 'upload.html', {
            'uploaded_file_url': uploaded_file_url
        })
    return render(request, 'upload.html')

七、作业和练习

1. 实现一个完整的CRUD操作系统
2. 创建自定义的中间件
3. 实现文件上传和下载功能
4. 编写RESTful风格的URL设计
5. 实现用户认证和授权系统

八、扩展阅读

1. Django CBV (Class-Based Views) 详解
2. Django中间件开发最佳实践
3. RESTful API设计原则
4. Django安全最佳实践

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