Google app engine 文件操作

Mar 22, 200912

AI-generated summary

The Google App Engine currently does not allow users to manipulate the file system, so uploaded images can only be accessed through the database. However, it is possible to read files on the system using the code provided. The code also demonstrates how to dynamically display a logo image from the database in the shop table. The image can be accessed through a specific URL format, and can be displayed in template files.

GAE 目前还不允许用户操作文件系统，上传的图片只能通过数据库存取。但可以读取在系统上的文件

f=open(".img/a.jpg","rb")
self.response.out.write(f.read())
f.close()
下面转载：
通过数据库存取，以下的代码实现了 shop 表中 logo 图片的动态显示：
class showShopLogo(webapp.RequestHandler):
def get(self):
shopid = self.request.get('sid')
shop = Shop.get_by_id(int(shopid))
if (shop and shop.logo):
img = images.Image(shop.logo)
img.resize(width=128, height=128)
tumbimg = img.execute_transforms(output_encoding=images.PNG)
self.response.headers['Content-Type'] = 'image/png'
self.response.out.write(tumbimg)
else:
self.redirect('/images/nologo.png')

定义处理路径：

application = webapp.WSGIApplication(
[　...
('/shop/logo', showShopLogo),
( ...)
], debug=True)
wsgiref.handlers.CGIHandler().run(application)

我们可以通过http://example.com/shop/logo?sid=5 这样的格式访问图片，在模板文件中，用实现图片的显示。