Google App Engine：404找不到资源

问题描述：

我想在Python中使用Google App Engine建立一个基本的网志模型。但是，我的代码的问题，我想，我得到一个404错误，当我试图显示所有发布的博客条目在一个页面上。这里是python代码：

I am trying to build a basic blog model using Google App Engine in Python. However, something's wrong with my code I suppose, and I am getting a 404 error when I try to display all the posted blog entries on a single page. Here's the python code:

import os
import re
import webapp2
import jinja2
from string import letters
from google.appengine.ext import db

template_dir = os.path.join(os.path.dirname(__file__), 'templates')
jinja_env = jinja2.Environment(loader = jinja2.FileSystemLoader(template_dir),     autoescape=True)

class Handler(webapp2.RequestHandler):
    def write(self, *a, **kw):
        self.response.out.write(*a, **kw)
    def render_str(self, template, **params):
        t = jinja_env.get_template(template)
        return t.render(params)
    def render(self, template, **kw):
        self.write(self.render_str(template, **kw))

def post_key(name = "dad"):
    return db.Key.from_path('blog', name)

class Blogger(db.Model):
    name = db.StringProperty()
    content = db.TextProperty()
    created = db.DateTimeProperty(auto_now_add = True)

    def render(self):
        self._render_text = self.content.replace('\n', '<br>')
        return render_str("post.html", p = self)

class MainPage(Handler):
    def get(self):
        self.response.write("Visit our blog")

class BlogHandler(Handler):
    def get(self):
        posts = db.GqlQuery("SELECT * FROM Blogger order by created desc")
        self.render("frontblog.html", posts = posts)    

class SubmitHandler(Handler):
    def get(self):
        self.render("temp.html")    
    def post(self):
        name = self.request.get("name")
        content = self.request.get("content")
        if name and content:
            a = Blogger(name = name, content = content, parent = post_key())
            a.put()
            self.redirect('/blog/%s' % str(a.key().id()))
        else:
            error = "Fill in both the columns!"
            self.render("temp.html", name = name, content = content, error =     error)        

class DisplayPost(Handler):
    def get(self, post_id):
        po = Blogger.get_by_id(int(post_id))
        if po:
            self.render("perma.html", po = po)
        else:
            self.response.write("404 Error")        

app = webapp2.WSGIApplication([('/', MainPage),
                          ('/blog', BlogHandler), 
                          ('/blog/submit', SubmitHandler),
                          ('/blog/([0-9]+)', DisplayPost)], debug=True)

发布我的内容后，它被重定向到一个固定链接。但是，这是我提交我的帖子的错误：

After posting my content, it gets redirected to a permalink. However, this is the error I am getting on submitting my post:

404 Not Found
The resource could not be found

这里是frontblog.html源代码，万一有帮助：

Here's the frontblog.html source code, in case that would help:

<!DOCTYPE html>
<html>
<head>

  <title>CS 253 Blog</title>
</head>

<body>
  <a href="/blog">
    CS 253 Blog
  </a>

  <div id="content">
  {% block content %}
      {%for post in posts%}
        {{post.render() | safe}}
        <br></br>
      {%endfor%}
  {% endblock %}
  </div>
</body>

</html>

所以基本上，我没有被重定向到永久链接页面。

So basically, I am not being redirected to the permalink page. What seems to be the problem?

答

当你创建你的帖子时，你会给它一个父（不知道为什么）。但是当你得到它，你这样做的ID只，不考虑父ID。在数据存储区中，键实际上是一个由所有父种类和ID /名称组成的路径，然后是当前实体的路径，并获取您需要传递完整路径的对象。

When you create your post, you're giving it a parent (not sure why). But when you get it, you do so by the ID only, and don't take into account the parent ID. In the datastore, a key is actually a path consisting of all the parent kinds and IDs/names and then those of the current entity, and to get an object you need to pass the full path.

可能的解决方案：

删除父键，因为它不会在这里做任何事将其设置为相同的值;

在获取对象时使用它： Blogger.get_by_id（post_id，parent = parent_key（））- - 显然这只有在父项始终相同时才有效;

在路径中使用完整的字符串键，而不仅仅是ID，并执行 Blogger。 get（key） - 您还需要更改路由正则表达式以接受字母数字字符，例如'/ blog /（\w +）'，并将重定向更改为'/ blog /％s'％a.key（）。

Drop the parent key, since it isn't doing anything here as you're always setting it to the same value;
Use it when you get the object: Blogger.get_by_id(post_id, parent=parent_key()) - obviously this only works if the parent is always the same;
Use the full stringified key in the path, rather than just the ID, and do Blogger.get(key) - you'll also need to change the route regex to accept alphanumeric chars, eg '/blog/(\w+)', and change the redirect to '/blog/%s' % a.key().

Google App Engine：404找不到资源

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