二十六、完成登录功能，用session记住用户名

登录功能完成：

js:设置return

function fnLogin() {
    var oUname = document.getElementById("uname");
    var oUpass = document.getElementById("upass");
    var oError = document.getElementById("error_box");

    oError.innerHTML = "<br>"
    // uname
    if (oUname.value.length > 20 || oUname.value.length < 6) {
        oError.innerHTML = "亲，用户名至少6-20位哦";
        return false;
    } 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";
        return false;
    } 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 = "用户名只能为字母或数字";
            return false;
        }
    }

// upass
    if (oUpass.value.length > 20 || oUpass.value.length < 6) {
    oError.innerHTML = "亲，密码至少6-20位哦";
    return false;
    }
    window.alert("用户登录成功！")
}

html:设置

form
input

onclick="return fnLogin()"

{% extends 'index.html' %}
{% block title %}登录{% endblock %}

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

{% block main %}
<body class="bg">
<div id="container">
    <div class="box">
        <h2 id="denglu">登录</h2>

        <div class="input_box">
            <input type="text" id="uname" placeholder="请输入用户名">
        </div>
        <div class="input_box">
            <input type="password" id="upass" placeholder="请输入密码">
        </div>
        <div class="error" id="error_box"><br></div>
        <div class="input_box">
            <button id="login" type="submit" onclick="fnLogin()">登录</button>
            <button id="cancel" type="cancel" onclick="fnLogin()">取消</button>
        </div>

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

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,redirect,url_for,request,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))
# db.create_all()

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


@app.route('/regist/',methods=['GET','POST'])
def regist():
    if request.method == 'GET':
        return render_template("regist.html")
    else:
        username = request.form.get("username")
        password = request.form.get("password")
        user = User.query.filter(User.username == username).first()
        if user:
            return 'username existed.'
        else:
            user = User(username=username, password=password)
            db.session.add(user) #数据库，添加操作
            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('login'))
            else:
                return '密码错误'
        else:
            return '用户名不存在'


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

import os

SQLALCHEMY_DATABASE_URI = 'mysql+pymysql://root:@127.0.0.1:3306/mis1121?charset=utf8'
SQLALCHEMY_TRACK_MODIFICATIONS = False

SECRET_KEY = os.urandom(24)

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原文地址：https://www.cnblogs.com/Green-/p/7887173.html