Python SQLAlchemy JSON作为blob/text

我使用MySQL将JSON作为blob/text存储在一列中。有没有一种简单的方法可以使用python/SQLAlchemy将其转换为dict？

如何

你可以很容易地使用SQLAlchemy

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对于SQLAlchemy版本>=0.7，请查看下面的内容

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定义表时可以使用此选项（示例使用elixir）：

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您还可以使用不同的json serialiser来处理jsonpickle。

我认为SQLAlchemy文档中的json示例也值得一提：

但是，我认为可以改进为对空字符串和空字符串不那么严格：

class JSONEncodedDict(TypeDecorator):
    impl = VARCHAR

    def process_bind_param(self, value, dialect):
        if value is None:
            return None
        return json.dumps(value, use_decimal=True)

    def process_result_value(self, value, dialect):
        if not value:
            return None
        return json.loads(value, use_decimal=True)

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这就是我根据以上两个答案得出的结论

import json

class JsonType(types.TypeDecorator):    

    impl = types.Unicode

    def process_bind_param(self, value, dialect):
        if value :
            return unicode(json.dumps(value))
        else:
            return {}

    def process_result_value(self, value, dialect):
        if value:
            return json.loads(value)
        else:
            return {}

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sqlalchemy.types.MutableType

已被弃用（从v0.7版开始），而是使用

sqlalchemy.ext.mutable

我找到了一个我已经测试过使用情况的by。到目前为止，它在词典和列表中都很有效

为子孙后代粘贴以下内容：

import simplejson
import sqlalchemy
from sqlalchemy import String
from sqlalchemy.ext.mutable import Mutable

class JSONEncodedObj(sqlalchemy.types.TypeDecorator):
    """Represents an immutable structure as a json-encoded string."""

    impl = String

    def process_bind_param(self, value, dialect):
        if value is not None:
            value = simplejson.dumps(value)
        return value

    def process_result_value(self, value, dialect):
        if value is not None:
            value = simplejson.loads(value)
        return value

class MutationObj(Mutable):
    @classmethod
    def coerce(cls, key, value):
        if isinstance(value, dict) and not isinstance(value, MutationDict):
            return MutationDict.coerce(key, value)
        if isinstance(value, list) and not isinstance(value, MutationList):
            return MutationList.coerce(key, value)
        return value

    @classmethod
    def _listen_on_attribute(cls, attribute, coerce, parent_cls):
        key = attribute.key
        if parent_cls is not attribute.class_:
            return

        # rely on "propagate" here
        parent_cls = attribute.class_

        def load(state, *args):
            val = state.dict.get(key, None)
            if coerce:
                val = cls.coerce(key, val)
                state.dict[key] = val
            if isinstance(val, cls):
                val._parents[state.obj()] = key

        def set(target, value, oldvalue, initiator):
            if not isinstance(value, cls):
                value = cls.coerce(key, value)
            if isinstance(value, cls):
                value._parents[target.obj()] = key
            if isinstance(oldvalue, cls):
                oldvalue._parents.pop(target.obj(), None)
            return value

        def pickle(state, state_dict):
            val = state.dict.get(key, None)
            if isinstance(val, cls):
                if 'ext.mutable.values' not in state_dict:
                    state_dict['ext.mutable.values'] = []
                state_dict['ext.mutable.values'].append(val)

        def unpickle(state, state_dict):
            if 'ext.mutable.values' in state_dict:
                for val in state_dict['ext.mutable.values']:
                    val._parents[state.obj()] = key

        sqlalchemy.event.listen(parent_cls, 'load', load, raw=True, propagate=True)
        sqlalchemy.event.listen(parent_cls, 'refresh', load, raw=True, propagate=True)
        sqlalchemy.event.listen(attribute, 'set', set, raw=True, retval=True, propagate=True)
        sqlalchemy.event.listen(parent_cls, 'pickle', pickle, raw=True, propagate=True)
        sqlalchemy.event.listen(parent_cls, 'unpickle', unpickle, raw=True, propagate=True)

class MutationDict(MutationObj, dict):
    @classmethod
    def coerce(cls, key, value):
        """Convert plain dictionary to MutationDict"""
        self = MutationDict((k,MutationObj.coerce(key,v)) for (k,v) in value.items())
        self._key = key
        return self

    def __setitem__(self, key, value):
        dict.__setitem__(self, key, MutationObj.coerce(self._key, value))
        self.changed()

    def __delitem__(self, key):
        dict.__delitem__(self, key)
        self.changed()

class MutationList(MutationObj, list):
    @classmethod
    def coerce(cls, key, value):
        """Convert plain list to MutationList"""
        self = MutationList((MutationObj.coerce(key, v) for v in value))
        self._key = key
        return self

    def __setitem__(self, idx, value):
        list.__setitem__(self, idx, MutationObj.coerce(self._key, value))
        self.changed()

    def __setslice__(self, start, stop, values):
        list.__setslice__(self, start, stop, (MutationObj.coerce(self._key, v) for v in values))
        self.changed()

    def __delitem__(self, idx):
        list.__delitem__(self, idx)
        self.changed()

    def __delslice__(self, start, stop):
        list.__delslice__(self, start, stop)
        self.changed()

    def append(self, value):
        list.append(self, MutationObj.coerce(self._key, value))
        self.changed()

    def insert(self, idx, value):
        list.insert(self, idx, MutationObj.coerce(self._key, value))
        self.changed()

    def extend(self, values):
        list.extend(self, (MutationObj.coerce(self._key, v) for v in values))
        self.changed()

    def pop(self, *args, **kw):
        value = list.pop(self, *args, **kw)
        self.changed()
        return value

    def remove(self, value):
        list.remove(self, value)
        self.changed()

def JSONAlchemy(sqltype):
    """A type to encode/decode JSON on the fly

    sqltype is the string type for the underlying DB column.

    You can use it like:
    Column(JSONAlchemy(Text(600)))
    """
    class _JSONEncodedObj(JSONEncodedObj):
        impl = sqltype
    return MutationObj.as_mutable(_JSONEncodedObj)

---

根据@snapshoe answer和回复@Timmy的评论：

您可以通过使用属性来实现这一点。以下是一个表格示例：

class Providers(Base):
    __tablename__ = "providers"
    id = Column(
        Integer,
        Sequence('providers_id', optional=True),
        primary_key=True
    )
    name = Column(Unicode(40), index=True)
    _config = Column("config", Unicode(2048))

    @property
    def config(self):
        if not self._config:
            return {}
        return json.loads(self._config)

    @config.setter
    def config(self, value):
        self._config = json.dumps(value)

    def set_config(self, field, value):
        config = self.config
        config[field] = value
        self.config = config

    def get_config(self):
        if not self._config:
            return {}
        return json.loads(self._config)

    def unset_config(self, field):
        config = self.get_config()
        if field in config:
            del config[field]
            self.config = config

现在，您可以在

Providers（）

对象上使用它：

>>> p = Providers()
>>> p.set_config("foo", "bar")
>>> p.get_config()
{"foo": "bar"}
>>> a.config
{u'foo': u'bar'}

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我知道这是一个老生常谈的问题，也许已经过时了，但我希望这能帮助到一些人。

这方面的秘诀如下：

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作为对之前回答的更新，我们已经成功地使用了这些回答。从MySQL 5.7和SQLAlchemy 1.1开始，您可以使用，这将为您提供更好的性能和免费的整体

它还允许您创建JSON元素

---

但当然，只有在将逻辑移到数据库本身时，您才会将自己锁定在MySQL上运行应用程序。

谢谢，有办法自动完成吗？类似于sqlalchemy中的触发器。这对我不起作用。在类MutableType（对象）内：def copy_值引发异常。def copy_value（self，value）：“未实现。”“raise NOTEImplementedError（）我更改了源代码，它工作了，但我对这会导致的维护问题感到不舒服。回答很好。。。还要注意，PostgreSQL支持JSON类型。这看起来很有希望——与您的示例类似，但如果可用，将使用PostgreSQL JSON类型

MutableType

已被

sqlalchemy.ext.mutable

替换，是否可以更新上述类以使用它？@YogeshMangaj如果您想用ext.mutable提交单独的答案，我将参考它并投票。我现在没有办法测试新版本。保存时遇到问题，通过使用可变字典解决。注意：只有将该值视为不可变值时，这才有效。因此，可以为对象属性指定一个完整的

dict

。如果您试图只修改dict的元素，sqlalchemy将不会注册更改，也不会在刷新时保存更改。请参见

sqlalchemy.ext.mutable.mutable

，了解如何更改该值。

import simplejson
import sqlalchemy
from sqlalchemy import String
from sqlalchemy.ext.mutable import Mutable

class JSONEncodedObj(sqlalchemy.types.TypeDecorator):
    """Represents an immutable structure as a json-encoded string."""

    impl = String

    def process_bind_param(self, value, dialect):
        if value is not None:
            value = simplejson.dumps(value)
        return value

    def process_result_value(self, value, dialect):
        if value is not None:
            value = simplejson.loads(value)
        return value

class MutationObj(Mutable):
    @classmethod
    def coerce(cls, key, value):
        if isinstance(value, dict) and not isinstance(value, MutationDict):
            return MutationDict.coerce(key, value)
        if isinstance(value, list) and not isinstance(value, MutationList):
            return MutationList.coerce(key, value)
        return value

    @classmethod
    def _listen_on_attribute(cls, attribute, coerce, parent_cls):
        key = attribute.key
        if parent_cls is not attribute.class_:
            return

        # rely on "propagate" here
        parent_cls = attribute.class_

        def load(state, *args):
            val = state.dict.get(key, None)
            if coerce:
                val = cls.coerce(key, val)
                state.dict[key] = val
            if isinstance(val, cls):
                val._parents[state.obj()] = key

        def set(target, value, oldvalue, initiator):
            if not isinstance(value, cls):
                value = cls.coerce(key, value)
            if isinstance(value, cls):
                value._parents[target.obj()] = key
            if isinstance(oldvalue, cls):
                oldvalue._parents.pop(target.obj(), None)
            return value

        def pickle(state, state_dict):
            val = state.dict.get(key, None)
            if isinstance(val, cls):
                if 'ext.mutable.values' not in state_dict:
                    state_dict['ext.mutable.values'] = []
                state_dict['ext.mutable.values'].append(val)

        def unpickle(state, state_dict):
            if 'ext.mutable.values' in state_dict:
                for val in state_dict['ext.mutable.values']:
                    val._parents[state.obj()] = key

        sqlalchemy.event.listen(parent_cls, 'load', load, raw=True, propagate=True)
        sqlalchemy.event.listen(parent_cls, 'refresh', load, raw=True, propagate=True)
        sqlalchemy.event.listen(attribute, 'set', set, raw=True, retval=True, propagate=True)
        sqlalchemy.event.listen(parent_cls, 'pickle', pickle, raw=True, propagate=True)
        sqlalchemy.event.listen(parent_cls, 'unpickle', unpickle, raw=True, propagate=True)

class MutationDict(MutationObj, dict):
    @classmethod
    def coerce(cls, key, value):
        """Convert plain dictionary to MutationDict"""
        self = MutationDict((k,MutationObj.coerce(key,v)) for (k,v) in value.items())
        self._key = key
        return self

    def __setitem__(self, key, value):
        dict.__setitem__(self, key, MutationObj.coerce(self._key, value))
        self.changed()

    def __delitem__(self, key):
        dict.__delitem__(self, key)
        self.changed()

class MutationList(MutationObj, list):
    @classmethod
    def coerce(cls, key, value):
        """Convert plain list to MutationList"""
        self = MutationList((MutationObj.coerce(key, v) for v in value))
        self._key = key
        return self

    def __setitem__(self, idx, value):
        list.__setitem__(self, idx, MutationObj.coerce(self._key, value))
        self.changed()

    def __setslice__(self, start, stop, values):
        list.__setslice__(self, start, stop, (MutationObj.coerce(self._key, v) for v in values))
        self.changed()

    def __delitem__(self, idx):
        list.__delitem__(self, idx)
        self.changed()

    def __delslice__(self, start, stop):
        list.__delslice__(self, start, stop)
        self.changed()

    def append(self, value):
        list.append(self, MutationObj.coerce(self._key, value))
        self.changed()

    def insert(self, idx, value):
        list.insert(self, idx, MutationObj.coerce(self._key, value))
        self.changed()

    def extend(self, values):
        list.extend(self, (MutationObj.coerce(self._key, v) for v in values))
        self.changed()

    def pop(self, *args, **kw):
        value = list.pop(self, *args, **kw)
        self.changed()
        return value

    def remove(self, value):
        list.remove(self, value)
        self.changed()

def JSONAlchemy(sqltype):
    """A type to encode/decode JSON on the fly

    sqltype is the string type for the underlying DB column.

    You can use it like:
    Column(JSONAlchemy(Text(600)))
    """
    class _JSONEncodedObj(JSONEncodedObj):
        impl = sqltype
    return MutationObj.as_mutable(_JSONEncodedObj)

class Providers(Base):
    __tablename__ = "providers"
    id = Column(
        Integer,
        Sequence('providers_id', optional=True),
        primary_key=True
    )
    name = Column(Unicode(40), index=True)
    _config = Column("config", Unicode(2048))

    @property
    def config(self):
        if not self._config:
            return {}
        return json.loads(self._config)

    @config.setter
    def config(self, value):
        self._config = json.dumps(value)

    def set_config(self, field, value):
        config = self.config
        config[field] = value
        self.config = config

    def get_config(self):
        if not self._config:
            return {}
        return json.loads(self._config)

    def unset_config(self, field):
        config = self.get_config()
        if field in config:
            del config[field]
            self.config = config

>>> p = Providers()
>>> p.set_config("foo", "bar")
>>> p.get_config()
{"foo": "bar"}
>>> a.config
{u'foo': u'bar'}

from sqlalchemy.types import TypeDecorator, VARCHAR
import json

class JSONEncodedDict(TypeDecorator):
    """Represents an immutable structure as a json-encoded string.

    Usage::

        JSONEncodedDict(255)

    """

    impl = VARCHAR

    def process_bind_param(self, value, dialect):
        if value is not None:
            value = json.dumps(value)

        return value

    def process_result_value(self, value, dialect):
        if value is not None:
            value = json.loads(value)
        return value