高阶应用-缓存

187次阅读

共计 4694 个字符，预计需要花费 12 分钟才能阅读完成。

对于一个中等流量网站，尽可能地减少开销是很有必要的。缓存数据就是为了保护那些需要很多计算资源的结果，这样就不必在下次重新消耗资源进行计算

对于给定的网址，尝试从缓存中找到网址，如果页面在缓存中，直接返回缓存的页面，如果缓存中没有，一系列操作（比如查数据库）后，保存生成的页面内容到缓存系统以供下一次使用，然后返回生成的页面内容

减轻服务器的压力
提供良好的用户体验

缓存在数据库中

配置 settings.py

# 添加缓存配置 
CACHES = {'default':{'BACKEND':'django.core.cache.backends.db.DatabaseCache',
        'LOCATION':'my_cache_table',
        'OPTIONS':{'MAX_ENTRIES':'10',  # 缓存数据的最大条数 超出则自动清除 
        },
        'KEY_PREFIX':'cache', # 缓存前缀 
    }
}

生成缓存所需要的缓存表

python manage.py createcachetable [table_name]

python manage.py createcachetable my_cache_table

缓存在内存中

配置 settings.py

# 配置缓存在内存中 
CACHES = {'default':{'BACKEND':'django.core.cache.backends.locmem.LocMemCache',
    }
}

缓存在文件中

CACHES = {'default':{'BACKEND':'django.core.cache.backends.filebased.FileBasedCache',
        'LOCATION':r'C:\Users\xlg\Desktop\cache',
    }
}

缓存在 redis 中

安装第三方扩展库

pip install django-redis

配置

# 缓存在 redis 中 
CACHES = {'default':{'BACKEND':'django_redis.cache.RedisCache',
        'LOCATION':'redis://127.0.0.1:6379/1'
      
    }
}

cache_page 装饰器的参数：

time 秒过期的时间
cache 缓存配置默认为 default
key_prefix 缓存的前缀

from django.views.decorators.cache import cache_page

# 缓存的使用 
@cache_page(10)
def test_filter(req):
    print('你能看到我几次')
    u = User.objects.all()
    return render(req,'show_data.html',{'u':u})

导入

from django.core.cache import cache
缓存操作
- 设置
  
  cache.set(key,value,expires)
- 获取
  
  cache.get(key)
- 删除
  
  cache.delete(key)
- 清空
  
  cache.clear()

示例

from django.core.cache import cache
from django.template import loader

def my_cache(req):
    res = cache.get('user')
    if not res:
        u = User.objects.all()
        tem = loader.get_template('show_user.html')
        res = tem.render({'u':u})
        cache.set('user', res, 60)
    return HttpResponse(res)

settings.py 配置

# 缓存在 redis 中 
CACHES = {'default':{'BACKEND': 'django_redis.cache.RedisCache',
        'LOCATION': 'redis://127.0.0.1:6379/1',
    }
}

视图函数

def register(req):
    if req.method == 'GET':
        return render(req, 'register.html')
    elif req.method == 'POST':
        username = req.POST.get('username')
        userpass = req.POST.get('userpass')
        email = req.POST.get('email')
        if cache.get(username):
            return HttpResponse('该账户已存在')
        else:
            # 设置 None 为永远不过期 
            cache.set(username,userpass, None)
    return HttpResponse('成功')




def Login(req):
    if req.method == 'GET':
        return render(req, 'login.html')
    elif req.method == 'POST':
        username = req.POST.get('username')
        userpass = req.POST.get('userpass')
        email = req.POST.get('email')
        password = cache.get(username)
        if password and password == userpass:
            return HttpResponse('登录成功')
        else:
            return HttpResponse('请输入正确的用户名或密码')

登录 / 注册模板

<!DOCTYPE html>
<html>
<head>
    <title> 登录页面 </title>
<style>
        .pg_header{position: fixed;
            height: 48px;
            top: 0;
            left: 0;
            right: 0;
            background-color: #2459a2;
            line-height: 48px;
        }
        .pg_header .logo{margin: 0 auto;
            float: left;
            width: 200px;
            text-align: center;
            line-height: 48px;
            font-size: 28px;
            color: white;
        }
        .pg_dl{left: 400px;
            display: inline-block;
            padding: 0 40px;
            color: white;
        }
        .pg_header .pg_dl:hover{background-color: #2459fb;
            cursor: pointer;
        }
        .left{margin-top: 20px;
            width: 400px;
            display: inline-block;
            float: left;
        }
        .pg_body{margin-top: 50px;
            font-size: 18px;
            display: inline-block;
            width: 200px;
        }
        .pg_body .menu{width: 800px;
            padding: 15px;
            float: left;
            font-weight: bold;
        }
        input[type="text"]{width: 200px;
            height: 25px;
            border-radius: 6px;
        }
        input[type="password"]{width: 200px;
            height: 25px;
            border-radius: 6px;
        }
        input[type="button"]{background-color: #555555;
               border: none;
            color: white;
            padding: 12px 29px;
            text-align: center;
            text-decoration: none;
            display: inline-block;
            font-size: 17px;
            margin: 4px 2px;
            cursor: pointer;
            border-radius: 4px;
        }
        input[type="submit"]{background-color: #555555;
               border: none;
            color: white;
            padding: 12px 29px;
            text-align: center;
            text-decoration: none;
            display: inline-block;
            font-size: 17px;
            margin: 4px 2px;
            cursor: pointer;
            border-radius: 4px;
        }
        .kong{margin-top: -54px;
            margin-left: 200px;
            float:left;
            padding: 15px;
        }
        .img{width: 50px;
            height: 40px;
        }
        .can{width: 1220px;
            height: 40px;
            line-height: 40px;
            margin: 0 auto;
            text-align: center;
            display: inline-block;
        }
        .tian{color: red;
            float: right;
            font-size: 12px;
            margin-right: -120px;
            margin-top: -25px;
        }
    </style>
</head>
<body id="i88" style="margin: 0">
    <div class = "pg_header">
        <a class = "logo">LOGO</a>
        <a class="pg_dl" id="i77"> 登录 </a>
    </div>
    <form name="tijiao" method="post" onsubmit="return check()" action="{% url'App:login'%}">
        {% csrf_token %}
        <div class="left"></div>
        <div class="pg_body">
                <div class="menu"> 用户名:</div>
                    <div class="kong">
                        <input id="text1" type="text" name="username" placeholder="请输入用户名"><span id="div1" class="tian" style="margin-top: 4px">*(为必填)</span>
                    </div>

                <div class="menu"> 密码:</div>
                    <div class="kong">
                        <input id="text2" type="password" name="userpass" onblur="check()">
                        <span id="div2" class="tian" style="margin-top: 5px">*(为必填)</span>
                    </div>

        </div>
        <div class="can">
            <input id="i111" type="submit" name="002" value="登  录">
            <p style="width: 200px;display: inline-block;"></p>
            <input id="i222" type="button" name="004" value="取  消">
        </div>
    </form>
</body>
</html>

路由地址

from django.urls import path
from App.views import *

urlpatterns = [path('', main.index, name='index'),
    path(r'login/', main.Login, name='login'),
    path(r'register/', main.register, name='register'),
]