SQLAlchemy是Python中比较优秀的orm框架，在SQLAlchemy中定义了多种数据库表的对应关系，
其中一对多是一种比较常见的关系。利用flask sqlalchemy实现一对多的关系如下：
1. 建立数据库的模型
在本次试验中建立三个表： user, phone ,atttr。user 和phone, phone 和atttr均为一对多的关系。实现如下：
#!/usr/bin/env python
# -*- coding: utf-8 -*- from flask import Flask
from flask.ext.sqlalchemy import SQLAlchemy app = Flask(__name__) # 配置数据库
app.config[
'SQLALCHEMY_DATABASE_URI'] = \
"mysql://root: root@127.0.0.1/test?charset=utf8"
db = SQLAlchemy(app) # 建立user表
class Usr(db.Model):
__tablename__ = 'usr'
id = db.Column(db.Integer, primary_key=True)
usrname = db.Column(db.String(80), unique=True)
email = db.Column(db.String(120), unique=True)
phone = db.relationship('Phone', backref='user', lazy='dynamic') def __init__(self, username, email):
self.usrname = username
self.email = email class Phone(db.Model):
id = db.Column(db.Integer, primary_key=True)
name = db.Column(db.String(20))
factory = db.Column(db.String(20))
userId = db.Column(db.Integer, db.ForeignKey('usr.id'))
attr = db.relationship(
'Atttr', backref='phone', lazy='dynamic') def __init__(self, name, factory, userId):
self.name = name
self.factory = factory
self.userId = userId class Atttr(db.Model):
id = db .Column(db.Integer, primary_key=True)
color = db.Column(db.String(20))
price = db.Column(db.String(20))
macId = db.Column(db.Integer, db.ForeignKey('phone.id')) def __init__(self, color, price, macId):
self.color = color
self.price = price
self.macId = macId db.create_all()
user表和phone表的一对多的关系通过下面语句确定：
phone = db.relationship('Phone', backref='user', lazy='dynamic')
其中rrealtionship描述了user和phone的关系。在此文中，第一个参数为对应参照的类"Phone";
第二个参数backref为类Phone申明新属性的方法；第三个参数lazy决定了什么时候SQLALchemy从
数据库中加载数据。
2. 构造api获取数据资源
注意：在获取资源之前，先向数据库中写入测试数据
#!usr/bin/env pyhton
# -*- coding: utf-8 -*- from flask import Flask
from flask.ext.restful import reqparse, Api, Resource
from model import * app = Flask(__name__)
api = Api(app) def to_json(model):
""" Returns a JSON representation of an SQLAlchemy-backed object. """
json = {}
# json['fields'] = {}
# json['pk'] = getattr(model, 'id')
for col in model._sa_class_manager.mapper.mapped_table.columns:
# json['fields'][col.name] = getattr(model, col.name)
json[col.name] = getattr(model, col.name)
# return dumps([json])
return json def to_json_list(model_list):
json_list = []
for model in model_list:
json_list.append(to_json(model))
return json_list def message(record):
if record:
return to_json(record), 200
return {"message": "not exit"}, 400 class userResource(Resource): def get(self, id):
record = Usr.query.filter_by(id=id).first()
return to_json_list(record.phone.first().phone) def put(self, id):
parser = reqparse.RequestParser()
parser.add_argument('username', type=str)
args = parser.parse_args(strict=True)
record = Usr.query.filter_by(id=id).first()
if record:
record.username = args['username']
db.session.commit()
return {"status": "updated"}, 201
return {"message": "not exit"}, 400 def delete(self, id):
record = Usr.query.filter_by(id=id).first()
if record:
db.session.delete(record)
db.session.commit()
return {"status": "deleted"}, 204
return {"message": "not exit"}, 400
class AtrrResource(Resource):
def get(self, id):
record = Atttr.query.filter_by(id=id).first()
return message(record.phone.user)
api.add_resource(userResource, '/v1.0/user/<id>')
api.add_resource(usrList, '/v1.0/user', '/v1.0/user/')
api.add_resource(AtrrResource, '/v1.0/atrr/<id>')
if '__name__' == '__main__' :
app.run(DEBUG=True)
通过在浏览器中输入url: 127.0.0.1:5000/v1.0/user/1可以获得某用户的某种类型手机的所有属性。
主要为get函数，其通过三层访问，即可得到相关的信息。当然还可以通过查询某一手机的颜色获取其
用户的信息，如Atttr get所示。
参考资料：
[1] http://docs.jinkan.org/docs/flask-sqlalchemy/models.html#id3