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python - 从 SQLAlchemy、Flask 返回 JSON 对象，用于 3 个相关表

问题描述

我得到了这个模型model.py。它有 3 个表，Test,Area,Issue 一个测试有多个区域，每个区域有很多问题：

from sqlalchemy import Column, ForeignKey, Integer, String, DateTime
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import relationship
from sqlalchemy import create_engine
from sqlalchemy.sql import func

Base = declarative_base()


class Test(Base):

    __tablename__ = 'test'
    id = Column(Integer, primary_key=True)
    type = Column(String(30), nullable=False)
    number = Column(String(30))
    status = Column(String(30), nullable=False)
    start_date = Column(DateTime(timezone=True), server_default=func.now())
    closed_date = Column(DateTime(timezone=True), server_default=func.now())
    description = Column(String(500))
    contact = Column(String(200))

    @property
    def serialize(self):
        # Returns object data in easily serializable format
        return{
            'id': self.id,
            'type': self.type,
            'number': self.number,
            'status': self.status,
            'start_date': self.start_date,
            'closed_date': self.closed_date,
            'description': self.description,
            'contact': self.contact
        }


class Area(Base):

    __tablename__ = 'area'
    id = Column(Integer, primary_key=True)
    name = Column(String(30), nullable=False)
    test_id = Column(Integer, ForeignKey('test.id'))
    test = relationship(Test, backref='areas')

    @property
    def serialize(self):
        # Returns object data in easily serializable format
        return{
            'name': self.name,
            'id': self.id
        }


class Issue(Base):

    __tablename__ = 'issue'
    name = Column(String(80), nullable=False)
    id = Column(Integer, primary_key=True)
    reference_number = Column(String(20), nullable=True)
    status = Column(String(30), nullable=False)
    area_id = Column(Integer, ForeignKey('area.id'))
    area = relationship(Area, backref='issues')

    @property
    def serialize(self):
        # Returns object data in easily serializable format
        return{
            'name': self.name,
            'id': self.id,
            'reference_number': self.price,
            'status': self.status
        }


engine = create_engine('sqlite:///appsecurity.db?check_same_thread=False')
Base.metadata.create_all(engine)

我想为一个查询的结果返回一个 JSON，它将带回一个包含所有区域的测试以及每个区域内的所有问题：

这是 SQLAlchemy 查询：

def getTestWithAreasAndIssues(id):
    test = (session.query(Test, Area, Issue)
            .join(Area)
            .join(Issue)
            .options(
                joinedload(Test.areas).
                joinedload(Area.issues)
            )
            .filter(Test.id == id)
            .filter(Test.id == Area.test_id)
            .filter(Area.id == Issue.area_id)
            ).all()
    return test

在我看来这是正确的，相当于这个 sqlite3 查询：

sqlite> select * from test, area, issue where area.test_id=test.id and issue.area_id=area.id and test.id=4;

4|Web|Test 11111|Open|2018-07-23 01:59:11.932234|2018-07-23 01:59:11|Second Test With Issues Third Attemp|david@no.us|12|Encryption|4|Weak Encryption|1|701|12|N
4|Web|Test 11111|Open|2018-07-23 01:59:11.932234|2018-07-23 01:59:11|Second Test With Issues Third Attemp|david@no.us|12|Encryption|4|ATS not in used|2|702|12|N
4|Web|Test 11111|Open|2018-07-23 01:59:11.932234|2018-07-23 01:59:11|Second Test With Issues Third Attemp|david@no.us|13|Authentication|4|Basic Authentication|3|701|13|N
4|Web|Test 11111|Open|2018-07-23 01:59:11.932234|2018-07-23 01:59:11|Second Test With Issues Third Attemp|david@no.us|20|Information|4|Sensitive Information on disk|4|103|20|N
4|Web|Test 11111|Open|2018-07-23 01:59:11.932234|2018-07-23 01:59:11|Second Test With Issues Third Attemp|david@no.us|20|Information|4|Password stored in cookies |5|104|20|N
4|Web|Test 11111|Open|2018-07-23 01:59:11.932234|2018-07-23 01:59:11|Second Test With Issues Third Attemp|david@no.us|20|Information|4|Not rate limited in API resources|6|701|20|N
sqlite>

为了进一步澄清，这里是 sqlalchemy 的结果：

这是 SQLALchemy 的回复

[(<model.Test object at 0x7f15322e8190>, <model.Area object at 0x7f15322e8210>, <model.Issue object at 0x7f15322e8450>), 
(<model.Test object at 0x7f15322e8190>, <model.Area object at 0x7f15322e8210>, <model.Issue object at 0x7f15322e8710>), 
(<model.Test object at 0x7f15322e8190>, <model.Area object at 0x7f15322e82d0>, <model.Issue object at 0x7f15322e83d0>), 
(<model.Test object at 0x7f15322e8190>, <model.Area object at 0x7f15322e8650>, <model.Issue object at 0x7f15322e8950>), 
(<model.Test object at 0x7f15322e8190>, <model.Area object at 0x7f15322e8650>, <model.Issue object at 0x7f15322e88d0>), 
(<model.Test object at 0x7f15322e8190>, <model.Area object at 0x7f15322e8650>, <model.Issue object at 0x7f15322e8850>)]

有人可以帮我找到某种方法来从中返回 JSON 对象吗？

标签： pythonjsonpython-2.7flaskflask-sqlalchemy

解决方案

这个文件没有问题我有问题并且调用了错误的函数，但是文件本身没问题，我可以正确调用 json.dumps(result) 并将正确的 JSON 返回给用户，如下所示 from flask

response = make_response(json.dumps(result,cls=MyEncoder1), 200) response.headers['Content-Type'] = 'application/json' 返回响应

我使用 cls 参数解决了编码日期时间的问题，因为 json.dumps 在解码日期时间参数时失败

在此处查看编码器的代码

    #!/usr/bin/env python3
from datetime import datetime
import json

class MyEncoder1(json.JSONEncoder):
    def default(self, obj):
        """
        default method is used if there is an unexpected object type.
        datetime will be converted to string
        """
        if isinstance(obj, datetime):
            obj = str(obj)
        else:
            obj = super(MyEncoder1, self).default(obj)
        print obj
        return obj

谢谢，我希望这篇文章能帮助任何在使用 Flask 和 SQLAlchemy 进行 JSON 操作的人。

我希望看到对本准则的改进 哪些方面可以做得不同，哪些方面可以做得更好

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