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

py文件

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)
    Telphone = db.Column(db.String(20), nullable=True)


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


@app.route('/login/', methods=['GET', 'POST'])
def login():
    if request.method == 'GET':
        return render_template('login.html')
    else:
        usern = request.form.get('Username')
        passn = request.form.get('Password')
        user = User.query.filter(User.Username == usern).first()
        if user:
            if user.Password == passn:
                session['user'] = usern
                return redirect(url_for('base'))
            else:
                return '密码错误'
                # return window.alert("密码错误")
        else:
            # return window.alert("用户名不存在")
            return '用户名不存在'



@app.route('/register/', methods=['GET', 'POST'])
def register():
    if request.method == 'GET':
        return render_template('register.html')
    else:
        usern = request.form.get('Username')
        passn = request.form.get('Password')
        teln = request.form.get('Telphone')
        user = User.query.filter(User.Username == usern).first()
        if user:
            return '用户名已经存在'
        else:
            user1 = User(Username=usern, Password=passn, Telphone=teln)
            db.session.add(user1)
            db.session.commit()
            return redirect(url_for('login'))


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


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

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

js文件

function myLogin() {
    var oUname = document.getElementById("uname");
    var oError = document.getElementById("error_box");
    var oUpass = document.getElementById("upass");
    var isError = true;
    oError.innerHTML = "<br>"
    if ((oUname.value.length < 6) || (oUname.value.length > 20)) {
        oError.innerHTML = "用户名必须为6-20位"
        isError = false;
        return isError;

    }
    else if ((oUname.value.charCodeAt(0) >= 48) && (oUname.value.charCodeAt(0) <= 57)) {
        oError.innerHTML = "用户名首位必须为字母"
        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 = "用户名必须为字母或数字"
                isError = false;
                return isError;
            }
        }
    if ((oUpass.value.length < 6) || (oUpass.value.length > 20)) {
        oError.innerHTML = "密码必须6-20位"
        isError = false;
        return isError;
    }
    return isError;
    //return window.alert("登录成功")
}

html文件

{% extends 'base.html' %}
{% block title %}登录界面{% endblock %}
{% block head %}
    <script type="text/javascript" src="{{ url_for('static',filename='js/login-register.js') }}"></script>
    <link rel="stylesheet" type="text/css" href="{{ url_for('static',filename='css/login-register.css') }}">
{% endblock %}
{% block main %}
    <form action="{{ url_for('login') }}" method="post">
    <div class="container">
        <div class="box">
            <a href="{{ url_for ('login') }}" class="active">登录</a>
            <a>*</a>
            <a href="{{ url_for ('register') }}" class="active">注册</a></div>
        <div class="input_box"><br><br>
            Username:<input id="uname" type="text" placeholder="请输入用户名" name="Username"><br><br><br><br>
            Password:<input id="upass" type="password" placeholder="请输入密码" name="Password"><br><br></div>
        <div class="check_box">
            <input type="checkbox" checked="checked">记住我
        </div>


        <div id="error_box"></div>
        <div>
            <button id="login" type="submit" onclick=" return myLogin()">登录</button>
        </div>
    </div>
{% endblock %}

截图：