python-GAE NDB Blobstore Google高性能图片服务

我正在制作一个用于上传文本和图像的应用程序.我已经阅读了很多有关blobstore和Google高性能图片服务的文章,最后我找到了一种将它们全部实现的方法.

我想知道的是,是否一切都做得好或可以做得更好,以及将serving_url保存在模型中还是更好,还是必须在每次我要在页面中打印图像时进行计算.

只有一个用户和一个图片.

这是代码(概述,忘记我的custom.PageHandler,它仅具有轻松呈现页面的功能以及用于检查表单值的内容,等等)：

class User(ndb.Model):
    """ A User """
    username = ndb.StringProperty(required=True)
    password = ndb.StringProperty(required=True)
    email = ndb.StringProperty(required=True)

class Picture(ndb.Model):
    """ All pictures that a User has uploaded """
    title = ndb.StringProperty(required=True)
    description = ndb.StringProperty(required=True)
    blobKey = ndb.BlobKeyProperty(required=True)
    servingUrl = ndb.StringProperty()
    created = ndb.DateTimeProperty(auto_now_add=True)
    user = ndb.KeyProperty(kind=User)

# This class shows the user pics
class List(custom.PageHandler):
    def get(self):
        # Get the actual user pics
        pics = Picture.by_user(self.user.key)
        for pic in pics:
            pic.servingUrl = images.get_serving_url(pic.blobKey, size=90, crop=True)
        self.render_page("myPictures.htm", data=pics)

# Get and post for the send page
class Send(custom.PageHandler, blobstore_handlers.BlobstoreUploadHandler):
    def get(self):
        uploadUrl = blobstore.create_upload_url('/addPic')
        self.render_page("addPicture.htm", form_action=uploadUrl)

    def post(self):
        # Create a dictionary with the values, we will need in case of error
        templateValues = self.template_from_request()
        # Test if all data form is valid
        testErrors = check_fields(self)

        if testErrors[0]:
            # No errors, save the object
            try:
                # Get the file and upload it
                uploadFiles = self.get_uploads('picture')
                # Get the key returned from blobstore, for the first element
                blobInfo = uploadFiles[0]
                # Add the key to the template
                templateValues['blobKey'] = blobInfo.key()

                # Save all
                pic = Picture.save(self.user.key, **templateValues)
                if pic is None:
                    logging.error('Picture save error.')

                self.redirect("/myPics")

            except:
                self.render_page("customMessage.htm", custom_msg=_("Problems while uploading the picture."))
        else:
            # Errors, render the page again, with the values, and showing the errors
            templateValues = custom.prepare_errors(templateValues, testErrors[1])
            # The session for upload a file must be new every reload page
            templateValues['form_action'] = blobstore.create_upload_url('/addPic')

            self.render_page("addPicture.htm", **templateValues)

基本上,我列出所有图片,并在此行的jinja2模板中显示图像：

{% for line in data %}
  <tr>
    <td class="col-center-data"><img src="{{ line.servingUrl }}"></td>

因此,在List类中,我计算每个服务网址并将其临时添加到Model中.我不确切知道将其直接保存在模型中是否会很好,因为我不知道URL是否会随时间变化.图片的网址将是永久的吗？在那种情况下,我可以保存它而不是计算,是吗？

Send类仅显示用于上载图像的表单,并将数据保存到模型.在重新渲染页面的情况下,我总是生成一个新的form_action链接,因为文档对此进行了讨论.这样对吗？

该代码正在运行,但就性能和节省资源而言,我想知道哪种方法更好.

解决方法:

你是对的.您确实想保存get_serving_url()而不是重复调用它.它保持不变.

请注意,使用完网址后,就像删除Blob一样,有一个delete_serving_url().

标签：blobstore,app-engine-ndb,google-app-engine,image,python
来源： https://codeday.me/bug/20191030/1969913.html