Google App Engine - JSON GeoPt 数据序列化

Question

我正在尝试为我的 Web 应用程序创建一个 API，但在尝试将 GeoPtProperty 加载到 JSON 时我总是收到错误消息。我尝试将 GeoPt 数据转换为 JSON 对象，但没有成功。

class Post(ndb.Model):
    content = ndb.StringProperty(required = True)
    user = ndb.StringProperty()
    coords = ndb.GeoPtProperty()

    def render(self):
        self._render_text = self.content.replace('\n', '<br>')
        params = dict(p = self)

        return render_str("post.html", **params)

    def as_dict(self):
        d = {'content': self.content,
             'user': self.user,
             'coords': self.coords}

        return d

class Handler(webapp2.RequestHandler): 
    def write(self, *a, **kw):
        self.response.out.write(*a, **kw)

    def render_json(self, d):
        json_txt = json.dumps(d)
        self.response.headers['Content-Type'] = 'application/json; charset=UTF-8'
        self.write(json_txt)

class MainPage(Handler):        
    def get(self):
        posts = Post.query(ancestor=post_key()).order(-Post.created)

    if self.format == 'json':
        self.response.headers['Access-Control-Allow-Origin'] = '*'
        return self.render_json([p.as_dict() for p in posts])

下面是回溯

Traceback (most recent call last):
  File "/base/data/home/runtimes/python27/python27_lib/versions/third_party/webapp2-2.5.2/webapp2.py", line 1535, in __call__
    rv = self.handle_exception(request, response, e)
  File "/base/data/home/runtimes/python27/python27_lib/versions/third_party/webapp2-2.5.2/webapp2.py", line 1529, in __call__
    rv = self.router.dispatch(request, response)
  File "/base/data/home/runtimes/python27/python27_lib/versions/third_party/webapp2-2.5.2/webapp2.py", line 1278, in default_dispatcher
    return route.handler_adapter(request, response)
  File "/base/data/home/runtimes/python27/python27_lib/versions/third_party/webapp2-2.5.2/webapp2.py", line 1102, in __call__
    return handler.dispatch()
  File "/base/data/home/runtimes/python27/python27_lib/versions/third_party/webapp2-2.5.2/webapp2.py", line 572, in dispatch
    return self.handle_exception(e, self.app.debug)
  File "/base/data/home/runtimes/python27/python27_lib/versions/third_party/webapp2-2.5.2/webapp2.py", line 570, in dispatch
    return method(*args, **kwargs)
  File "/base/data/home/apps/s~website/1.396738651304801066/main.py", line 121, in get
    return self.render_json([p.as_dict() for p in posts])
  File "/base/data/home/apps/s~website/1.396738651304801066/main.py", line 45, in render_json
    json_txt = json.dumps(d)
  File "/base/data/home/runtimes/python27/python27_dist/lib/python2.7/json/__init__.py", line 243, in dumps
    return _default_encoder.encode(obj)
  File "/base/data/home/runtimes/python27/python27_dist/lib/python2.7/json/encoder.py", line 207, in encode
    chunks = self.iterencode(o, _one_shot=True)
  File "/base/data/home/runtimes/python27/python27_dist/lib/python2.7/json/encoder.py", line 270, in iterencode
    return _iterencode(o, 0)
  File "/base/data/home/runtimes/python27/python27_dist/lib/python2.7/json/encoder.py", line 184, in default
    raise TypeError(repr(o) + " is not JSON serializable")
TypeError: datastore_types.GeoPt(37.636003000000002, 127.216528) is not JSON serializable

如何在 JSON 中正确接收数据？

Answer 1

我终于想通了，我会回答我自己的问题。 GeoPt 数据无法序列化，因此必须将其转换为 JSON 对象。在存储 GeoPT 时，您可以简单地使用以下代码。

        if coords:
            coords = ndb.GeoPt(lat, lon)
            p.coords = coords
        p.put()

ndb 数据存储实体如下所示：

class Post(ndb.Model):
    coords = ndb.GeoPtProperty()

我能够获取纬度和经度，并将它们转换为 JSON 对象。

coords = self.coords.lat, self.coords.lon
lat, lon = coords[0], coords[1]
coords = {'latitude': lat, 'longitude': lon}

这成功了，我的应用程序不再抛出错误。

Google App Engine - JSON GeoPt 数据序列化

Google App Engine - JSON Serialization of GeoPt data

python

google-app-engine

serialization

json

webapp2