完成登录功能，用session记住用户名

登录功能完成：

1. js:设置return
2. html:设置
   1. form
   2. input

   3. onclick="return fnLogin()"

3. py:
   1. @app.route设置methods
   2. GET
   3. POST
      1. 读取表单数据
      2. 查询数据库
         1. 用户名密码对：
            1. 记住用户名
            2. 跳转到首页
         2. 用户名密码不对：
            1. 提示相应错误。

session：

1. 从`flask`中导入`session`
2. 设置`SECRET_KEY`
3. 操作字典一样操作`session`：增加用户名`session['username']=`username

from flask import Flask,render_template,request,redirect,url_for,session
from flask_sqlalchemy import SQLAlchemy
import config

app = Flask(__name__)
app.config.from_object(config)
db=SQLAlchemy(app)

class User(db.Model):
    __tablename__= 'User'
    id = db.Column(db.Integer,primary_key=True,autoincrement=True)
    username = db.Column(db.String(20),nullable=False)
    password = db.Column(db.String(20), nullable=False)
    nickname = db.Column(db.String(20), nullable=True)

db.create_all()

@app.route('/')
def shouye():
    return render_template('shouye.html')

@app.route('/zhuce/',methods=['GET','POST'])
def zhuce():
    if request.method=='GET':
        return render_template('zhuce.html')
    else:
        usern=request.form.get('username')
        passw=request.form.get('password')
        user=User.query.filter(User.username==usern).first()
        if user:
            return u'用户已存在'
        else:
            user1=User(username=usern,password=passw)
            db.session.add(user1)
            db.session.commit()
            return  redirect(url_for('denglu'))

@app.route('/denglu/',methods=['GET','POST'])
def denglu():
    if request.method=='GET':
        return render_template('denglu.html')
    else:
        usern=request.form.get('username')
        passw=request.form.get('password')
        user=User.query.filter(User.username==usern).first()
        if user:
            if user.password==passw:
                session['user']=usern
                return redirect(url_for('shouye'))
            else:
                return u'密码错误！'
        else:
            return u'用户不存在！'

@app.route('/wenda/')
def wenda():
    return render_template('wenda.html')

if __name__ == '__main__':
    app.run(debug=True)

import os

SQLALCHEMY_DATABASE_URI = 'mysql+pymysql://root:@localhost:3306/mis?charset=utf8'
SQLALCHEMY_TRACK_MODIFICATIONS = False

SECRET_KEY=os.urandom(24)

登录html

{% extends'shouye.html' %}

{% block title %}
用户登录
{% endblock %}

{% block js %}
 <script src="{{ url_for('static',filename='js/kk.js') }}">
 </script>
{% endblock %}

{% block jiemian %}
<div  id="container" style="width:500px;margin: 0 auto " >
    <form  action="{{ url_for("denglu") }}" method="post">
        <div id="header" style="background-color:mediumaquamarine;height: 40px"><h2 align="center" style="margin-bottom:0;font-size: 33px;font-family: 楷体" >用户登录</h2></div>
        <div id="content" style="background-color:#EEEEEE;height: 250px;width:500px;float:left;text-align:center;font-size: 22px">
            <div class="input-box">
                <br>用户名<input id="un" type="text" name="username" placeholder="请输入用户账号"style="height: 20px">
            </div>
            <div class="input-box">
                <br>密码<input id="pw" type="password" name="password"style="height: 20px"><br>
            </div>
               <br><input type="radio">普通用户
                <input type="radio">VIP用户
            <div class="input-box">
{#               <br><input  type="submit" value="登录" onclick="myLogin()" style="width:65px;height:25px;font-size:15px">#}
{#              <input type="button"value="注册"onclick="youLogin()" style="width:65px;height:25px;font-size:15px"><br>#}
                <br><button onclick="myLogin()"style="width:65px;height:25px;font-size:15px">登录</button>
             <div id="error_box" style="font-size: 25px"><br></div>
            </div>
        </div>
        <div id="footer" style="background-color:mediumaquamarine;clear:both;text-align:center;height: 40px;font-size: 31px;font-family: 楷体">版权*GZCC</div>
    </form>
</div>
{% endblock %}