Flask搭建api服务的实现步骤

2022-11-13 10:11:21 服务 搭建 步骤

flask是一个使用 python 编写的轻量级 WEB 应用框架,很适合个人开发,我们在此处做一个接口。

为方便调试,本文使用get接口方式。get接口十分简单,不需要上传任何数据,在路径后面添加一个get方法就可以用,返回的是字符串

本文只是Flask开发的接口的初步文档,从最简单的接口开发到稍微复杂一些的接口,后续如有时间,会逐步完善,包括token鉴权、跨域认证、蓝图应用、日志管理等等。

9f93e13632d9b5a77f3ea76746b87714.png

第一步,首先在configs中配置数据源

configs.py

HOST = '127.0.0.1'
PORT = '5432'
DATABASE = 'runoobdb'
USERNAME = 'postgres'
PASSWord = '*****'
# 配置主数据库
DB_URI = "postgresql+psycopg2://{username}:{password}@{host}:{port}/{db}".fORMat(username=USERNAME, password=PASSWORD,
                                                                                 host=HOST, port=PORT, db=DATABASE)
# sqlALCHEMY_DATABASE_URI = 'postgresql+psycopg2://postgres:*****@127.0.0.1:5432/runoobdb'
# 连接其他数据库
SQLALCHEMY_BINDS = {
    'xxxdb': 'postgresql+psycopg2://postgres:123456@localhost:5432/lincms3',
    'yyydb': 'postgresql+psycopg2://postgres:123456@localhost:5432/lincms4',
    'zzzdb': 'sqlite:///users.db'
}
SQLALCHEMY_DATABASE_URI = DB_URI
SQLALCHEMY_TRACK_MODIFICATioNS = False
SQLALCHEMY_ECHO = True

第二步,在exts中定义全局db

exts.py

from flask_sqlalchemy import SQLAlchemy
db = SQLAlchemy()

第三步,构造了一个flaskutils,在这里定义一些接口应用到的公共类,比如数据转码,将数据集转换为JSON,解析url逗号参数等等,后续将在此基础上拓展功能。

flaskutils.py

import decimal
 
import numpy as np
import json, datetime,configparser
 
 
class DataEncoder(json.JSONEncoder):
    """数据转码类    """
    def default(self, obj):
        """针对无法转json的数据类型进行转码
        目前支持的转码类型        1、将Numpy的intger,floating转为int和float
        2、将Numpy的ndarray转为list
        3、将np.datetime64转化为字符串前10位        4、将datetime.datetime转化为"%Y-%m-%d %H:%M:%S"
        5、将datetime.date转化为"%Y-%m-%d"
        6、将bytes转化为utf-8字符串
        入参:
            obj: 数据对象
        出参:
            转化后的数据
        异常:
            无        """
        if isinstance(obj, np.integer):
            return int(obj)
        elif isinstance(obj, np.floating):
            return float(obj)
        elif isinstance(obj, np.ndarray):
            return obj.tolist()
        elif isinstance(obj, np.datetime64):
            return str(obj)[:10]
        elif isinstance(obj, datetime.datetime):
            return obj.strftime("%Y-%m-%d %H:%M:%S")
        elif isinstance(obj, datetime.date):
            return obj.strftime("%Y-%m-%d")
        elif isinstance(obj, decimal.Decimal):
            return float(obj)
        elif isinstance(obj, bytes):
            return str(obj, encoding='utf-8')
        else:
            return json.JSONEncoder.default(self, obj)
 
 
def getsqlresultjson(db, sql,params={}):
    """根据db和sql语句,将结果集转换为json格式
    根据db和sql语句,将结果集转换为json格式
    第一步:根据cursor获取元数据,生成键值列表
    第二步:遍历结果集,将键值列表和结果集组装成字典,加入列表
    第三步:将列表通过DataEncoder进行转码
    入参:
        db: 数据库实例.
        sql: 待运行的SQL语句
    出参:
        Json格式:
        举例:        {'Serak': ('Rigel VII', 'Preparer'),
          'Zim': ('Irk', 'Invader'),
         'Lrrr': ('Omicron Persei 8', 'Emperor')}
    异常:
        无    """
    resultdict = []
 
    cursor = db.session.execute(sql,params=params).cursor
    resultproxy = db.session.execute(sql,params=params).fetchall()
 
    # 获取元数据
    colname = [i[0] for i in cursor.description]
    # 获取结果集,组成字典,加入列表
    for rowproxy in resultproxy:
        rowresult = dict(zip(colname, rowproxy))
        resultdict.append(rowresult)
 
    # 生成json格式
    jsonstr = json.dumps(resultdict, cls=DataEncoder)
    return jsonstr
 
 
def parasecommaparamtolist(param):
    '''
    处理in传递参数,in传递参数可适用于两种传递方式,逗号传递参数或参数传递
    此处主要是处理,逗号传递参数,返回为list
    # Http://127.0.0.1:5000/getresultbysqlgetparaminbylist?sqlid=sql10&begindate=2018&enddate=2020&kpicode=03010101
    # http://127.0.0.1:5000/getresultbysqlgetparaminbylist?sqlid=sql10&begindate=2018&enddate=2020&kpicode=03010101&kpicode=031111111
    # http://127.0.0.1:5000/getresultbysqlgetparaminbylist?sqlid=sql10&begindate=2018&enddate=2020
    # http://127.0.0.1:5000/getresultbysqlgetparaminbylist?sqlid=sql10&begindate=2018&enddate=2020&kpicode=03010101,222222222
    # http://127.0.0.1:5000/getresultbysqlgetparaminbylist?sqlid=sql10&begindate=2018&enddate=2020&kpicode=03010101&kpicode=03010101
    :param param:
    :return:
        字符串列表    '''
    result = []
    for val in param.split(','):
        if val:
            result.append(val)
    return result

第四步,在app文件构建初始版本

app.py

import configs
from exts import db
from flask import Flask
from flaskutils import *
from flask import request,jsonify
 
app = Flask(__name__)
 
# 加载配置文件
app.config.from_object(configs)
app.debug = True
 
db.init_app(app)
 
if __name__ == '__main__':
    print(app.url_map)
    app.run(host='0.0.0.0', port=8080)

第五步,在app文件中配置sql语句,原本想尝试一下mybis类型的配置文件,后来决定简化;主要包括三条sql,第一条不需要传参,第二条传递常规参数,第三条传递in参数,尤其是in参数,基本上网上找到的方法都不可靠,本文算是原创吧。

sqldict={}
sqldict['sql1'] = """select a.*
from kpi_value a
where a.kpicode in ('01010101','02010101','03010101')
and a.datelevel='01'
and a.regionlevel='02'
"""
sqldict['sql2'] = """select a.*
from kpi_value a
where a.kpicode in ('01010101','02010101','03010101')
and a.datelevel='01'
and a.regionlevel='02'
and a.datecode>=:begindate and a.datecode<=:enddate
"""
sqldict['sql3'] = """select a.*
from kpi_value a
and a.datelevel='01'
and a.regionlevel='02'
and a.datecode>=:begindate and a.datecode<=:enddate
and a.kpicode in :kpicode
"""

1、构造第一个最简单sql返回接口,不需要传递sql参数,但需要传递sqlid参数

@app.route('/getresultbysql', methods=['GET', 'POST'])
def index1():
    sqlid = request.args.get('sqlid')
    sqltext=sqldict[sqlid]
    jsonstr = getsqlresultjson(db,sqltext)
    return jsonstr, 200, {"Content-Type": "application/json"}

2、构造一个sql内部传参的接口,通过字典参数方式

@app.route('/getresultbysqlparam', methods=['GET', 'POST'])
def index2():
    sqlid = request.args.get('sqlid')
    sqltext=sqldict[sqlid]
    params = {"begindate": '2017',"enddate":'2019'}
    jsonstr = getsqlresultjson(db,sqltext,params)
    return jsonstr, 200, {"Content-Type": "application/json"}

3、通过url进行sql参数的传递。

@app.route('/getresultbysqlgetparam', methods=['GET', 'POST'])
def index3():
    sqlid = request.args.get('sqlid')
    begindate = request.args.get('begindate')
    enddate = request.args.get('enddate')
    sqltext=sqldict[sqlid]
    params = {"begindate": begindate,"enddate":enddate}
    jsonstr = getsqlresultjson(db,sqltext,params)
    return jsonstr, 200, {"Content-Type": "application/json"}

4、通过url进行sql参数的传递,不过不传递in参数,而是在路由函数汇总内部指定in参数

@app.route('/getresultbysqlgetparamin', methods=['GET', 'POST'])
def index4():
    sqlid = request.args.get('sqlid')
    sqlid='sql3'
    begindate = request.args.get('begindate')
    enddate = request.args.get('enddate')
    sqltext=sqldict[sqlid]
    incond = ['01010101',  '03010101']
    params = {"begindate": begindate,"enddate":enddate,'kpicode':tuple(incond)}
    jsonstr = getsqlresultjson(db,sqltext,params)
    return jsonstr, 200, {"Content-Type": "application/json"}

5、通过url进行in参数和普通参数的传递,这里可以支持两种方式,一种是&aa=xxx&aa=yyy,一种是aa=xxx,yyy。

@app.route('/getresultbysqlgetparaminbylist', methods=['GET', 'POST'])
def index5():
    sqlid = request.args.get('sqlid')
    sqlid='sql3'
    begindate = request.args.get('begindate')
    enddate = request.args.get('enddate')
    incond=request.args.getlist('kpicode')
 
    if len(incond) == 1 and ',' in incond[0]:
        incond = parasecommaparamtolist(incond[0])
 
    sqltext=sqldict[sqlid]
    params = {"begindate": begindate,"enddate":enddate,'kpicode':tuple(incond)}
    jsonstr = getsqlresultjson(db,sqltext,params)
 
    return jsonstr, 200, {"Content-Type": "application/json"}

6、标准化接口响应返回结果。

@app.route('/getresultbysqlgetparaminbylistresponse', methods=['GET', 'POST'])
def index6():
 
    retinfo={}
    errorflag=False
    retinfo['returncode'] = 200
    retinfo['returndata'] = ''
    retinfo['returninfo'] = '处理成果'
    sqlid = request.args.get('sqlid')
    begindate = request.args.get('begindate')
    enddate = request.args.get('enddate')
    incond = request.args.getlist('kpicode')
 
    if len(incond) == 1 and ',' in incond[0]:
        incond = parasecommaparamtolist(incond[0])
    if not incond:
        retinfo['returninfo']=retinfo['returninfo'] +'未传入KPI编码'
        errorflag=True
    if not begindate:
        retinfo['returninfo'] = retinfo['returninfo'] + '未传入开始时间'
        errorflag=True
    if not enddate:
        retinfo['returninfo'] = retinfo['returninfo'] + '未传入结束时间'
        errorflag=True
    if begindate>enddate:
        retinfo['returninfo'] = retinfo['returninfo'] + '开始时间大于结束时间'
        errorflag=True
    if errorflag==True:
        retinfo['returncode'] = 400
        response = jsonify(retinfo)
        response.status_code = 400
        return response
 
    sqltext = sqldict[sqlid]
    params = {"begindate": begindate, "enddate": enddate, 'kpicode': tuple(incond)}
    jsonstr = getsqlresultjson(db, sqltext, params)
    retinfo['returndata']  = jsonstr
    response = jsonify(retinfo)
    response.status_code = 200
    return response

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