完成登录功能，用session记住用户名

                

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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

login.html

{% extends'base.html' %}
    {% block title %}
    登录
    {% endblock %}
{% block head %}

    <link rel="stylesheet"type="text/css"href="{{ url_for('static',filename='css/login.css') }}">
    <script src="{{ url_for('static',filename='js/login.js') }}"></script>
{% endblock %}
{% block main %}
<div class="Outbox">
      <div class="box">
          <h2>欢迎来到博客园，代码改变世界！</h2>
          <h3>登录页面</h3>
        <form action="{{ url_for('login')}}" method="post">
        <div class="input_box">
           账号：<input id="umane"type="text"placeholder="请输入账号">
        </div>
        <div class="input_box">
           密码：<input id="upass"type="password"placeholder="请输入密码">
        </div>
          <div id="error_box"><br></div>
          <div class="input_box">
              <button onclick="myLogin()">登录</button>
               <button onclick=window.alert("请重新输入")>取消</button></div>

          </div>
</div>
{% endblock %}

 login.js

function myLogin() {
            var oUname = document.getElementById("umane");
            var oError = document.getElementById("error_box");
             var oUpass = document.getElementById("upass");
            oError.innerHTML = "<br>"
     //oUname
        if (oUname.value.length>12 || oUname.value.length<6){
            oError.innerHTML = "用户名必须为6到12位数";
            isError=false;
            return isError;
         } else if((oUname.value.charCodeAt(0)>=48) && oUname.value.charCodeAt(0)<=57){

            oError.innerHTML = "首字母不能为数字";
             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 = "用户名只能包含字母和数字";
                    isError=false;
                    return isError;
                }
            }


            if(upass.value.length>12 || upass.value.length<6){
                oError.innerHTML="密码为6到12位数";
                isError=false;
                return isError;
            }
            return isError;
            window.alert("已成功登陆")

        }

py

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):
    __table__name = '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()

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

@app.route('/zhuce/',methods=['GET','POST'])
def zhuce():
    if request.method =='GET':
        return  render_template('zhuce.html')
    else:
        usern = request.form.get('name')
        teln = request.form.get('password')
        passw = request.form.get('password1')
        user = User.query.filter(User.username==usern).first()
        if user:
            return 'username existed'
        else:
            user= User(username=usern,tel=teln,password=passw)
            db.session.add(user)
            db.session.commit()
            return redirect(url_for('login'))

@app.route('/login/', methods=['GET','POST'])
def login():
    if request.method == 'GET':
        return render_template('login.html')
    else:
        username = request.form.get('username')
        password = request.form.get('password')
        user = User.query.filter(User.username == username).first()
        if user:
            if user.password ==password:
                session['user'] = username
                return redirect(url_for('index'))
            else:
                return u'password error'
        else:
            return u'username is not existed'


@app.route('/question/',methods=['GET','POST'])
def question():
    return render_template('question.html')

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

 config.py

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