[英]How to make a 'permalink' detail page displaying two images in Google App Engine webapp2 guestbook tutorial
我正在關注Google App Engine教程 (這是GitHub上的完整演示代碼 ),並希望:
我無法理解:
A)如何編寫發布問候語后稱為的重定向代碼 ,以便將其重定向到/ greeting / numeric-id之類的URL。
B)如何編寫將用戶重定向到的詳細信息視圖和模板頁面 ,以便顯示問候ID和圖像 。
這是顯示我想要做什么的圖:
這是guestbook.py :
import os
import urllib
from google.appengine.api import images
from google.appengine.api import users
from google.appengine.ext import ndb
from google.appengine.ext.webapp import blobstore_handlers
from google.appengine.ext import blobstore
import jinja2
import webapp2
JINJA_ENVIRONMENT = jinja2.Environment(
loader=jinja2.FileSystemLoader(os.path.dirname(__file__)),
extensions=['jinja2.ext.autoescape'],
autoescape=True)
DEFAULT_GUESTBOOK_NAME = 'default_guestbook'
def guestbook_key(guestbook_name=None):
"""Constructs a Datastore key for a Guestbook entity with name."""
return ndb.Key('Guestbook', guestbook_name or 'default_guestbook')
class Author(ndb.Model):
"""Sub model for representing an author."""
identity = ndb.StringProperty(indexed=False)
email = ndb.StringProperty(indexed=False)
class Greeting(ndb.Model):
"""A model for representing an individual Greeting entry."""
author = ndb.StructuredProperty(Author)
date = ndb.DateTimeProperty(auto_now_add=True)
avatar = ndb.BlobProperty(indexed=False, required=True)
other = ndb.BlobProperty(indexed=False, required=True)
class MainPage(webapp2.RequestHandler):
def get(self):
self.response.out.write('<html><body>')
guestbook_name = self.request.get('guestbook_name')
greetings = Greeting.query(
ancestor=guestbook_key(guestbook_name)) \
.order(-Greeting.date) \
.fetch(10)
self.response.out.write("""
<form action="/sign?%s"
enctype="multipart/form-data"
method="post">
<label>Avatar:</label>
<input type="file" name="avatar"/><br>
<label>Other Image:</label>
<input type="file" name="other"/><br>
<input type="submit" value="Submit">
</form>
</body>
</html>""" % (urllib.urlencode({'guestbook_name': guestbook_name})))
class Image(webapp2.RequestHandler):
""" Handle image stored as blobs of bytes.
No idea how the template knows to select a particular one. """
def get(self):
avatar_greeting_key = ndb.Key(urlsafe=self.request.get('avatar_id'))
other_greeting_key = ndb.Key(urlsafe=self.request.get('other_id'))
avatar_greeting = avatar_greeting_key.get()
other_greeting = other_greeting_key.get()
if avatar_greeting.avatar:
self.response.headers['Content-Type'] = 'image/png'
self.response.out.write(avatar_greeting.avatar)
elif other_greeting.other:
self.response.headers['Content-Type'] = 'image/png'
self.response.out.write(other_greeting.other)
else:
self.response.out.write('No image')
class Guestbook(webapp2.RequestHandler):
def post(self):
guestbook_name = self.request.get('guestbook_name',
DEFAULT_GUESTBOOK_NAME)
greeting = Greeting(parent=guestbook_key(guestbook_name))
if users.get_current_user():
greeting.author = Author(
identity=users.get_current_user().user_id(),
email=users.get_current_user().email())
avatar = self.request.get('avatar')
avatar = images.resize(avatar, 100, 100)
other = self.request.get('other')
other = images.resize(other, 400, 300)
greeting.avatar = avatar
greeting.other = other
greeting.put()
query_params = {'guestbook_name': guestbook_name}
self.redirect('/greeting/%d' % greeting.key.id())
class Detail(webapp2.RequestHandler):
""" Individual greeting. """
def get(self, *args, **kwargs):
guestbook_name = self.request.get('guestbook_name', DEFAULT_GUESTBOOK_NAME)
greeting = Greeting.get_by_id(args[0],
parent=guestbook_key(guestbook_name))
template_values = {
'greeting': greeting,
}
template = JINJA_ENVIRONMENT.get_template('detail.html')
self.response.write(template.render(template_values))
app = webapp2.WSGIApplication([
('/', MainPage),
('/img', Image),
('/sign', Guestbook),
('/greeting/(\d+)', Detail),
], debug=True)
我的detail.html模板:
<!DOCTYPE html>
{% autoescape true %}
<html>
<head>
<title>Greeting {{ greeting.id }}</title>
</head>
<body>
<h2>Greeting {{ greeting.id }}</h2>
Avatar: <img src="/img?avatar_id={{ greeting.key.urlsafe() }}">
<br>
Other: <img src="/img?other_id={{ greeting.key.urlsafe() }}">
</body>
</html>
{% endautoescape %}
我的app.yaml很有用:
runtime: python27
api_version: 1
threadsafe: true
# Handlers match in order, put above the default handler.
handlers:
- url: /stylesheets
static_dir: stylesheets
- url: /.*
script: guestbook.app
libraries:
- name: webapp2
version: latest
- name: jinja2
version: latest
錯誤:
Traceback (most recent call last):
File "/Users/simon/Projects/google-cloud-sdk/platform/google_appengine/lib/webapp2-2.5.2/webapp2.py", line 1535, in __call__
rv = self.handle_exception(request, response, e)
File "/Users/simon/Projects/google-cloud-sdk/platform/google_appengine/lib/webapp2-2.5.2/webapp2.py", line 1529, in __call__
rv = self.router.dispatch(request, response)
File "/Users/simon/Projects/google-cloud-sdk/platform/google_appengine/lib/webapp2-2.5.2/webapp2.py", line 1278, in default_dispatcher
return route.handler_adapter(request, response)
File "/Users/simon/Projects/google-cloud-sdk/platform/google_appengine/lib/webapp2-2.5.2/webapp2.py", line 1102, in __call__
return handler.dispatch()
File "/Users/simon/Projects/google-cloud-sdk/platform/google_appengine/lib/webapp2-2.5.2/webapp2.py", line 572, in dispatch
return self.handle_exception(e, self.app.debug)
File "/Users/simon/Projects/google-cloud-sdk/platform/google_appengine/lib/webapp2-2.5.2/webapp2.py", line 570, in dispatch
return method(*args, **kwargs)
File "/Users/simon/Projects/guestbook/guestbook.py", line 111, in get
self.response.write(template.render(template_values))
File "/Users/simon/Projects/google-cloud-sdk/platform/google_appengine/lib/jinja2-2.6/jinja2/environment.py", line 894, in render
return self.environment.handle_exception(exc_info, True)
File "/Users/simon/Projects/guestbook/detail.html", line 9, in top-level template code
Avatar: <img src="/img?avatar_id={{ greeting.key.urlsafe() }}">
UndefinedError: 'None' has no attribute 'key'
任何幫助,甚至更好的示例代碼,將不勝感激。 帶有詳細示例代碼,列表視圖和模板的示例的GAE / webapp2博客教程會很棒,但是GAE BlobStore的數據結構是否不是博客的理想選擇?
更新:如果我添加了Dan的答案中提供的python檢查代碼,則會收到500錯誤而不是堆棧跟蹤信息,並且如果我嘗試進行模板檢查,則會得到空白的問候頁面。 我用完整的代碼和解釋我要做什么的圖表更新了問題。
我將從B
開始:
該錯誤指示所述greeting
值是None
,導致一個異常時的Jinja2試圖擴大greeting.key
在{{ greeting.key.urlsafe() }}
模板呈現期間。
一種選擇是重新排列處理程序代碼,以防止在未滿足必要條件的情況下呈現該模板,可能符合以下要求:
...
greeting = Greeting.get_by_id(args[0])
if not greeting or not isinstance(greeting.key, ndb.Key):
# can't render that template, invalid greeting.key.urlsafe()
webapp2.abort(500)
return
template_values = {
'greeting': greeting,
}
template = JINJA_ENVIRONMENT.get_template('detail.html')
self.response.write(template.render(template_values))
...
另外,您也可以通過適當的檢查來包裝引用變量的模板區域(恕我直言,更丑陋,更困難,更脆弱,比起jinja2,Python對這種邏輯的方式要好得多),大致如下:
{% if greeting and greeting.key %}<img src="/img?avatar_img_id={{ greeting.key.urlsafe() }}">{% endif %}
現在到A
簡而言之-不是一個好主意,主要是因為您要在URL中使用的數字ID除了在同一個父實體下的問候語之外不是唯一的 ! 。 這在某種程度上解釋了為什么問候無效導致B
答案出錯的原因。
greeting = Greeting.get_by_id(args[0])
將返回None
除非您還創建了一個問候語實體,該問候語實體帶有您要傳入args[0]
且沒有父項的ID !
為了通過ID獲得您創建的問候語:
greeting = Greeting(parent=guestbook_key(guestbook_name))
您需要致電:
greeting = Greeting.get_by_id(args[0],
parent=guestbook_key(guestbook_name))
如果您想朝着同一方向繼續,也可以在問候URL中對guestbook_name
進行編碼,這將使您還可以獲得所需的父鍵,也許是以下幾行:
/guestbook/<guestbook_name>/greeting/<numeric-id>.
您還需要仔細查看圖像處理。 您存在架構上的不一致:在圖和模型中,您的頭像和另一個圖像都附加到一個問候實體上,但是在Image
處理程序中,它們每個都附加到了單獨的問候上。 處理程序也根本不會映射到圖像的URL(根據體系結構的決定,該URL還需要用於定位適當圖像的數據的其他編碼)。
恐怕您還需要做很多工作,直到您將整個事情都付諸實踐,遠遠超出了僅適合一個SO問題的范圍。 退后一步,重新考慮您的體系結構,將其拆分為較小的部分,一次只關注一個部分,然后繼續進行下去。 在熟悉了各個部分的技術之后,您會立即感覺到更好地解決整個問題。
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