Google App Engine模型的JSON序列化 [英] JSON serialization of Google App Engine models
本文介绍了Google App Engine模型的JSON序列化的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
模特:
class照片(db.Model):
filename = db.StringProperty()
title = db.StringProperty()
description = db.StringProperty(multiline = True)
date_taken = db。 DateTimeProperty()
date_uploaded = db.DateTimeProperty(auto_now_add = True)
album = db.ReferenceProperty(Album,collection_name ='photo')
解决方案
一个简单的递归函数可以用来将一个实体(以及任何对象)转换为一个可以传递给 simplejson
:
导入日期时间
导入时间
SIMPLE_TYPES =(int,long,float,bool,dict,basestring,list)
def to_dict(模型):
output = {}
$ b $如果value为None或isinstance(value,SIMPLE_TYPES):$ b,则为model.properties()中的key,prop中的iteritems():
value = getattr(model,key)
$ b output [key] = value
elif isinstance(value,datetime.date):
#将date / datetime转换为MILLISECONDS-since-epoch(JSnew Date())。
ms = time.mktime(value.utctimetuple())* 1000
ms + = getattr(value,'microseconds',0)/ 1000
output [key] = int(ms)
elif isinstance(value,db.GeoPt):
output [key] = {'lat':value.lat,'lon':value.lon}
elif isinstance(value,db .model):
output [key] = to_dict(value)
else:
raise ValueError('can not encode'+ repr(prop))
return output
I've been searching for quite a while with no success. My project isn't using Django, is there a simple way to serialize App Engine models (google.appengine.ext.db.Model) into JSON or do I need to write my own serializer?
Model:
class Photo(db.Model):
filename = db.StringProperty()
title = db.StringProperty()
description = db.StringProperty(multiline=True)
date_taken = db.DateTimeProperty()
date_uploaded = db.DateTimeProperty(auto_now_add=True)
album = db.ReferenceProperty(Album, collection_name='photo')
解决方案
A simple recursive function can be used to convert an entity (and any referents) to a nested dictionary that can be passed to simplejson
:
import datetime
import time
SIMPLE_TYPES = (int, long, float, bool, dict, basestring, list)
def to_dict(model):
output = {}
for key, prop in model.properties().iteritems():
value = getattr(model, key)
if value is None or isinstance(value, SIMPLE_TYPES):
output[key] = value
elif isinstance(value, datetime.date):
# Convert date/datetime to MILLISECONDS-since-epoch (JS "new Date()").
ms = time.mktime(value.utctimetuple()) * 1000
ms += getattr(value, 'microseconds', 0) / 1000
output[key] = int(ms)
elif isinstance(value, db.GeoPt):
output[key] = {'lat': value.lat, 'lon': value.lon}
elif isinstance(value, db.Model):
output[key] = to_dict(value)
else:
raise ValueError('cannot encode ' + repr(prop))
return output
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