完成登录功能，用session记住用户名

登录功能完成：

js:设置return
html:设置
1. form
2. input
3. ```
onclick="return fnLogin()"
```
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：

从`flask`中导入`session`
设置`SECRET_KEY`
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(50))


#db.create_all()

#增加数据
user=User(username = 'mis1234',password = '111111')
db.session.add(user)
db.session.commit()

#查询数据
user=User.query.filter(user.username == 'mis1234').first()
print(user.id,user.username,user.password)


#修改数据
user=User.query.filter(user.username == 'mis3333').first()
user.password = '0000'
db.session.commit()

#删除数据
user=User.query.filter(user.username == 'mis3333').first()
db.session.delete(user)
db.session.commit()

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

@app.route('/denglu/',methods=['GET','POST'])
def gg():
    if request.method == 'GET':
        return render_template('denglu.html') #跳转登录
    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
                session['user_id'] =user.id
                session.parmanent = True
                return redirect(url_for('shouye'))
            else:
                return u'password error'
        else:
            return u'username is not existed'

@app.route('/zhuche/', methods=['GET','POST'])
def login ():
    if request.method =='GET':
        return render_template('zhuce.html')#跳转注册
    else:
        usern = request.form.get('username')
        passw = request.form.get('password')
        nickn = request.form.get('nickname')
        user = User.query.filter(User.username == usern).first()
        if user:
            return u'username existed'
        else:
            user1 = User(username = usern,password = passw,nickname=nickn)
            db.session.add(user1)#数据库操作
            db.session.commit()
            return redirect(url_for('gg'))



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

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

{% extends 'base.html' %}

{% block denglutitle %}登录{% endblock %}

{% block dengluhead %}
    <link href="../static/css/denglu.css" rel="stylesheet" type="text/css">
    <script src="../static/js/denglu.js"></script>
{% endblock %}

{% block denglubody %}
    <div class="box">
        <h2>登录</h2>
        <form action="{{ url_for('gg') }}" method="post">
        <div class="input_box">
            username：<input type="text" id="uname" placeholder="请输入用户名" name="username">
        </div>
        <div class="input_box">
            password：<input type="password" id="upass" placeholder="请输入密码" name="password">
        </div>
        <div id="error_box"><br></div>
        <div class="input_box">
            <button onclick="fnLogin()">Enter</button>
        </div>
        </form>
    </div>
{% endblock %}

function fnLogin(){
    var oUname = document.getElementById("uname");
    var oUpass = document.getElementById("upass");
    var oError = document.getElementById("error_box");
    var isError=true;
    oError.innerHTML="<br>";
    //uname
    if (oUname.value.length>10 || oUname.value.length < 6){

        oError.innerHTML="用户名必须是6-10位！";
        isError=false;
        return isError;
    }else if((oUname.value.charCodeAt(0)>=48)&& (oUname.value.charCodeAt(0))<=57){
        oError.innerHTML="用户名首字母不能是数字！";
        isError=false;
        return isError;
    }else for(var i=0;i<oUname.value.length;i++){
        if((oUname.value.charCodeAt(i)<48 || oUname.value.charCodeAt(i)>57) && (oUname.value.charCodeAt(i)<97 || oUname.value.charCodeAt(i)>122)){
            oError.innerHTML="用户名只能为数字和字母";
            isError=false;
            return isError;
        }


    }
    //upass
    if(oUpass.value.length>10 || oUpass.value.length<6 ){
        oError.innerHTML="用户密码6-10位！";
        return;
    }
    window.alert("登录成功！")
}

config.py

#SQLALCHEMY_DATABASE_URI = 'mysql+pymysql://root:wk21640913@127.0.0.1:3306/mis_1test?charset=utf8'
import  os
SQLALCHEMY_DATABASE_URI = 'mysql+pymysql://root:@127.0.0.1:3306/mis_1?charset=utf8'
SQLALCHEMY_TRACK_MODIFICATIONS = False
SECRET_KEY = os.urandom(24)