Django可以很好地自动序列化从DB返回到JSON格式的ORM模型。

如何序列化SQLAlchemy查询结果为JSON格式?

我试过jsonpickle。编码,但它编码查询对象本身。 我尝试了json.dumps(items),但它返回

TypeError: <Product('3', 'some name', 'some desc')> is not JSON serializable

将SQLAlchemy ORM对象序列化为JSON /XML真的那么难吗?它没有任何默认序列化器吗?现在序列化ORM查询结果是非常常见的任务。

我所需要的只是返回SQLAlchemy查询结果的JSON或XML数据表示。

需要在javascript datagird中使用JSON/XML格式的SQLAlchemy对象查询结果(JQGrid http://www.trirand.com/blog/)


当前回答

更详细的解释。 在你的模型中,添加:

def as_dict(self):
       return {c.name: str(getattr(self, c.name)) for c in self.__table__.columns}

str()是针对python3的,所以如果使用python2则使用unicode()。它应该有助于反序列化日期。如果不处理这些,你可以删除它。

现在可以像这样查询数据库

some_result = User.query.filter_by(id=current_user.id).first().as_dict()

需要First()来避免奇怪的错误。As_dict()现在将反序列化结果。反序列化之后,就可以将其转换为json了

jsonify(some_result)

其他回答

经过一番尝试,我想出了自己的解决方案

def to_dict(self):
    keys = self.__mapper__.attrs.keys()
    attrs = vars(self)
    return { k : attrs[k]  for k in keys}

自定义序列化和反序列化。

"from_json"(类方法)基于json数据构建一个Model对象。

“反序列化”只能在实例上调用,并将json中的所有数据合并到Model实例中。

"serialize" -递归序列化

需要__write_only__属性来定义只写属性(例如“password_hash”)。

class Serializable(object):
    __exclude__ = ('id',)
    __include__ = ()
    __write_only__ = ()

    @classmethod
    def from_json(cls, json, selfObj=None):
        if selfObj is None:
            self = cls()
        else:
            self = selfObj
        exclude = (cls.__exclude__ or ()) + Serializable.__exclude__
        include = cls.__include__ or ()
        if json:
            for prop, value in json.iteritems():
                # ignore all non user data, e.g. only
                if (not (prop in exclude) | (prop in include)) and isinstance(
                        getattr(cls, prop, None), QueryableAttribute):
                    setattr(self, prop, value)
        return self

    def deserialize(self, json):
        if not json:
            return None
        return self.__class__.from_json(json, selfObj=self)

    @classmethod
    def serialize_list(cls, object_list=[]):
        output = []
        for li in object_list:
            if isinstance(li, Serializable):
                output.append(li.serialize())
            else:
                output.append(li)
        return output

    def serialize(self, **kwargs):

        # init write only props
        if len(getattr(self.__class__, '__write_only__', ())) == 0:
            self.__class__.__write_only__ = ()
        dictionary = {}
        expand = kwargs.get('expand', ()) or ()
        prop = 'props'
        if expand:
            # expand all the fields
            for key in expand:
                getattr(self, key)
        iterable = self.__dict__.items()
        is_custom_property_set = False
        # include only properties passed as parameter
        if (prop in kwargs) and (kwargs.get(prop, None) is not None):
            is_custom_property_set = True
            iterable = kwargs.get(prop, None)
        # loop trough all accessible properties
        for key in iterable:
            accessor = key
            if isinstance(key, tuple):
                accessor = key[0]
            if not (accessor in self.__class__.__write_only__) and not accessor.startswith('_'):
                # force select from db to be able get relationships
                if is_custom_property_set:
                    getattr(self, accessor, None)
                if isinstance(self.__dict__.get(accessor), list):
                    dictionary[accessor] = self.__class__.serialize_list(object_list=self.__dict__.get(accessor))
                # check if those properties are read only
                elif isinstance(self.__dict__.get(accessor), Serializable):
                    dictionary[accessor] = self.__dict__.get(accessor).serialize()
                else:
                    dictionary[accessor] = self.__dict__.get(accessor)
        return dictionary

Python 3.7+和Flask 1.1+可以使用内置的数据类包

from dataclasses import dataclass
from datetime import datetime
from flask import Flask, jsonify
from flask_sqlalchemy import SQLAlchemy


app = Flask(__name__)
db = SQLAlchemy(app)


@dataclass
class User(db.Model):
  id: int
  email: str

  id = db.Column(db.Integer, primary_key=True, auto_increment=True)
  email = db.Column(db.String(200), unique=True)


@app.route('/users/')
def users():
  users = User.query.all()
  return jsonify(users)  


if __name__ == "__main__":
  users = User(email="user1@gmail.com"), User(email="user2@gmail.com")
  db.create_all()
  db.session.add_all(users)
  db.session.commit()
  app.run()

/users/路由现在将返回一个用户列表。

[
  {"email": "user1@gmail.com", "id": 1},
  {"email": "user2@gmail.com", "id": 2}
]

自动序列化相关模型

@dataclass
class Account(db.Model):
  id: int
  users: User

  id = db.Column(db.Integer)
  users = db.relationship(User)  # User model would need a db.ForeignKey field

jsonify(account)的响应是这样的。

{  
   "id":1,
   "users":[  
      {  
         "email":"user1@gmail.com",
         "id":1
      },
      {  
         "email":"user2@gmail.com",
         "id":2
      }
   ]
}

覆盖默认的JSON编码器

from flask.json import JSONEncoder


class CustomJSONEncoder(JSONEncoder):
  "Add support for serializing timedeltas"

  def default(o):
    if type(o) == datetime.timedelta:
      return str(o)
    if type(o) == datetime.datetime:
      return o.isoformat()
    return super().default(o)

app.json_encoder = CustomJSONEncoder      

安装simplejson by PIP安装simplejson并创建一个类

class Serialise(object):

    def _asdict(self):
        """
        Serialization logic for converting entities using flask's jsonify

        :return: An ordered dictionary
        :rtype: :class:`collections.OrderedDict`
        """

        result = OrderedDict()
        # Get the columns
        for key in self.__mapper__.c.keys():
            if isinstance(getattr(self, key), datetime):
                result["x"] = getattr(self, key).timestamp() * 1000
                result["timestamp"] = result["x"]
            else:
                result[key] = getattr(self, key)

        return result

并将这个类继承到每个orm类,这样这个_asdict函数就会注册到每个orm类,然后。 并在任何地方使用jsonify

我对使用(太多?)字典的看法:

def serialize(_query):
    #d = dictionary written to per row
    #D = dictionary d is written to each time, then reset
    #Master = dictionary of dictionaries; the id Key (int, unique from database) 
    from D is used as the Key for the dictionary D entry in Master
    Master = {}
    D = {}
    x = 0
    for u in _query:
        d = u.__dict__
        D = {}
        for n in d.keys():
           if n != '_sa_instance_state':
                    D[n] = d[n]
        x = d['id']
        Master[x] = D
    return Master

使用flask(包括jsonify)和flask_sqlalchemy将输出打印为JSON。

使用jsonify(serialize())调用该函数。

与我迄今为止尝试过的所有SQLAlchemy查询一起工作(运行SQLite3)