（五）Flask 序列化对象封装及自定义json返回类型

问题场景：

解决统一响应文本封装及json响应文本类型错误问题

❤举个栗子

def get_user():
    uid = g.user.uid
    user = User.query.filter_by(id=uid).first_or_404()
    return jsonify(user)

报错：

TypeError: Object of type 'User' is not JSON serializable // Werkzeug Debugger

如上user返回值是一个对象，而jsonify无法将对象序列化，那怎么解决呢？

将user对象转换为字典，我们可以能会想到直接 user.__dict__

class Solution(object):
    name = 'wyq'
    age = 89

    def __init__(self):
        self.gender = '女'


o = Solution()
print(o.__dict__)

结果如下不是我们想要的，python中类变量是不会存放到__dict__,只有实例变量才会存入。

{'gender': '女'}

那么，如果获取到__dict__下的所有实例变量和类变量，我们就可以用jsonify序列化对象

❤解决方案

class Solution(object):
    name = 'wyq'
    age = 89

    def __init__(self):
        self.gender = '女'

    def keys(self):
        return ['name', 'age', 'gender']

    def __getitem__(self, item):
        return getattr(self, item)


o = Solution()
print(dict(o))

运行结果

{'name': 'wyq', 'age': 89, 'gender': '女'}

解决Flask中的json类型错误

Flask json转换类如下，只需要我们重新写default函数，定义转换规则，便能到达我们想要的效果。

class JSONEncoder(_json.JSONEncoder):
    """The default Flask JSON encoder.  This one extends the default simplejson
    encoder by also supporting ``datetime`` objects, ``UUID`` as well as
    ``Markup`` objects which are serialized as RFC 822 datetime strings (same
    as the HTTP date format).  In order to support more data types override the
    :meth:`default` method.
    """

    def default(self, o):
        """Implement this method in a subclass such that it returns a
        serializable object for ``o``, or calls the base implementation (to
        raise a :exc:`TypeError`).

        For example, to support arbitrary iterators, you could implement
        default like this::

            def default(self, o):
                try:
                    iterable = iter(o)
                except TypeError:
                    pass
                else:
                    return list(iterable)
                return JSONEncoder.default(self, o)
        """
        if isinstance(o, datetime):
            return http_date(o.utctimetuple())
        if isinstance(o, date):
            return http_date(o.timetuple())
        if isinstance(o, uuid.UUID):
            return str(o)
        if hasattr(o, '__html__'):
            return text_type(o.__html__())
        return _json.JSONEncoder.default(self, o)

在user对象中（也就是user的model），定义keys和__getitem__方法,key方法个性化可以放到对象中，getitem固定不变建议放入Base基类中

class User(Base):
    id = Column(Integer, primary_key=True)
    email = Column(String(24), unique=True, nullable=False)
    nickname = Column(String(24), unique=True)
    auth = Column(SmallInteger, default=1)
    _password = Column('password', String(100))

    def keys(self):
        return ['id', 'email', 'nickname', 'auth']
    
    def __getitem__(self, item):
        return getattr(self, item)

自定义Flask json解析类(app.py)

# -*- coding:utf-8 -*-
from flask import Flask as _Flask
from flask.json import JSONEncoder as _JSONEncoder
from app.libs.error_code import ServerError


class JSONEncoder(_JSONEncoder):
    def default(self, o):
        if hasattr(o, 'keys') and hasattr(o, '__getitem__'):
            return dict(o)
        raise ServerError()

使用自定义Flask json解析类

from flask import Flask
from app import JSONEncoder

app = Flask(__name__)

# 返回json格式转换
app.json_encoder = JSONEncoder

if __name__ == "__main__":
    app.run()

测试

image.png

最后，如果返回时间类型，或其他类型，需要在default，添加你想转换的类型

# -*- coding:utf-8 -*-
import datetime
import decimal
import uuid

from flask import Flask as _Flask
from flask.json import JSONEncoder as _JSONEncoder
from app.libs.error_code import ServerError


class JSONEncoder(_JSONEncoder):
    def default(self, o):
        if hasattr(o, 'keys') and hasattr(o, '__getitem__'):
            return dict(o)
        if isinstance(o, datetime.datetime):
            # 格式化时间
            return o.strftime("%Y-%m-%d %H:%M:%S")
        if isinstance(o, datetime.date):
            # 格式化日期
            return o.strftime('%Y-%m-%d')
        if isinstance(o, decimal.Decimal):
            # 格式化高精度数字
            return str(o)
        if isinstance(o, uuid.UUID):
            # 格式化uuid
            return str(o)
        if isinstance(o, bytes):
            # 格式化字节数据
            return o.decode("utf-8")
        raise ServerError()