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

你可以像这样将RowProxy转换为dict:

 d = dict(row.items())

然后将其序列化为JSON(必须为datetime值等指定编码器) 如果您只想要一条记录(而不是相关记录的完整层次结构),这并不难。

json.dumps([(dict(row.items())) for row in rs])

其他回答

下面的代码将sqlalchemy结果序列化为json。

import json
from collections import OrderedDict


def asdict(self):
    result = OrderedDict()
    for key in self.__mapper__.c.keys():
        if getattr(self, key) is not None:
            result[key] = str(getattr(self, key))
        else:
            result[key] = getattr(self, key)
    return result


def to_array(all_vendors):
    v = [ ven.asdict() for ven in all_vendors ]
    return json.dumps(v) 

叫有趣,

def all_products():
    all_products = Products.query.all()
    return to_array(all_products)

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)

我知道这是一个相当老的帖子。我采取了@SashaB给出的解决方案,并根据我的需要进行了修改。

我添加了以下内容:

字段忽略列表:序列化时要忽略的字段列表 字段替换列表:包含在序列化时要被值替换的字段名的字典。 删除方法和BaseQuery被序列化

我的代码如下:

def alchemy_json_encoder(revisit_self = False, fields_to_expand = [], fields_to_ignore = [], fields_to_replace = {}):
   """
   Serialize SQLAlchemy result into JSon
   :param revisit_self: True / False
   :param fields_to_expand: Fields which are to be expanded for including their children and all
   :param fields_to_ignore: Fields to be ignored while encoding
   :param fields_to_replace: Field keys to be replaced by values assigned in dictionary
   :return: Json serialized SQLAlchemy object
   """
   _visited_objs = []
   class AlchemyEncoder(json.JSONEncoder):
      def default(self, obj):
        if isinstance(obj.__class__, DeclarativeMeta):
            # don't re-visit self
            if revisit_self:
                if obj in _visited_objs:
                    return None
                _visited_objs.append(obj)

            # go through each field in this SQLalchemy class
            fields = {}
            for field in [x for x in dir(obj) if not x.startswith('_') and x != 'metadata' and x not in fields_to_ignore]:
                val = obj.__getattribute__(field)
                # is this field method defination, or an SQLalchemy object
                if not hasattr(val, "__call__") and not isinstance(val, BaseQuery):
                    field_name = fields_to_replace[field] if field in fields_to_replace else field
                    # is this field another SQLalchemy object, or a list of SQLalchemy objects?
                    if isinstance(val.__class__, DeclarativeMeta) or \
                            (isinstance(val, list) and len(val) > 0 and isinstance(val[0].__class__, DeclarativeMeta)):
                        # unless we're expanding this field, stop here
                        if field not in fields_to_expand:
                            # not expanding this field: set it to None and continue
                            fields[field_name] = None
                            continue

                    fields[field_name] = val
            # a json-encodable dict
            return fields

        return json.JSONEncoder.default(self, obj)
   return AlchemyEncoder

希望它能帮助到一些人!

扁平化实现

你可以使用这样的代码:

from sqlalchemy.ext.declarative import DeclarativeMeta

class AlchemyEncoder(json.JSONEncoder):

    def default(self, obj):
        if isinstance(obj.__class__, DeclarativeMeta):
            # an SQLAlchemy class
            fields = {}
            for field in [x for x in dir(obj) if not x.startswith('_') and x != 'metadata']:
                data = obj.__getattribute__(field)
                try:
                    json.dumps(data) # this will fail on non-encodable values, like other classes
                    fields[field] = data
                except TypeError:
                    fields[field] = None
            # a json-encodable dict
            return fields

        return json.JSONEncoder.default(self, obj)

然后转换为JSON使用:

c = YourAlchemyClass()
print json.dumps(c, cls=AlchemyEncoder)

它将忽略不可编码的字段(将它们设置为“None”)。

它不会自动展开关系(因为这可能导致自引用,并永远循环)。

递归的非循环实现

然而,如果你宁愿永远循环,你可以使用:

from sqlalchemy.ext.declarative import DeclarativeMeta

def new_alchemy_encoder():
    _visited_objs = []

    class AlchemyEncoder(json.JSONEncoder):
        def default(self, obj):
            if isinstance(obj.__class__, DeclarativeMeta):
                # don't re-visit self
                if obj in _visited_objs:
                    return None
                _visited_objs.append(obj)

                # an SQLAlchemy class
                fields = {}
                for field in [x for x in dir(obj) if not x.startswith('_') and x != 'metadata']:
                    fields[field] = obj.__getattribute__(field)
                # a json-encodable dict
                return fields

            return json.JSONEncoder.default(self, obj)

    return AlchemyEncoder

然后对对象进行编码,使用:

print json.dumps(e, cls=new_alchemy_encoder(), check_circular=False)

这将编码所有的子代、子代、子代……基本上可以编码你的整个数据库。当它到达之前编码过的东西时,它会将其编码为“None”。

递归的、可能是循环的、有选择的实现

另一种选择,可能更好,是能够指定你想要展开的字段:

def new_alchemy_encoder(revisit_self = False, fields_to_expand = []):
    _visited_objs = []

    class AlchemyEncoder(json.JSONEncoder):
        def default(self, obj):
            if isinstance(obj.__class__, DeclarativeMeta):
                # don't re-visit self
                if revisit_self:
                    if obj in _visited_objs:
                        return None
                    _visited_objs.append(obj)

                # go through each field in this SQLalchemy class
                fields = {}
                for field in [x for x in dir(obj) if not x.startswith('_') and x != 'metadata']:
                    val = obj.__getattribute__(field)

                    # is this field another SQLalchemy object, or a list of SQLalchemy objects?
                    if isinstance(val.__class__, DeclarativeMeta) or (isinstance(val, list) and len(val) > 0 and isinstance(val[0].__class__, DeclarativeMeta)):
                        # unless we're expanding this field, stop here
                        if field not in fields_to_expand:
                            # not expanding this field: set it to None and continue
                            fields[field] = None
                            continue

                    fields[field] = val
                # a json-encodable dict
                return fields

            return json.JSONEncoder.default(self, obj)

    return AlchemyEncoder

你现在可以调用它:

print json.dumps(e, cls=new_alchemy_encoder(False, ['parents']), check_circular=False)

例如,仅展开名为“parents”的SQLAlchemy字段。

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}