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 import Flask
   from flask_sqlalchemy import SQLAlchemy
   import config
   
   app = Flask(__name__)
   #app.config['SECRET_KEY'] = '1234567'
   app.config.from_object(config)
   db = SQLAlchemy(app)
   
   class User(db.Model):
       __tablename__ = 'user_test'
       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))
       tel = db.Column(db.String(20))
   
   #db.create_all()
   
   #2.在表中插入一条记录
   #user = User(username = 'mis1',password = '124', nickname='wk')
   #db.session.add(user)
   #db.session.commit()
   
   
   #3.去表中查询用户名对应的密码和接下来用户输入的密码是否相匹配
   #user = User.query.filter(User.username == 'mis1234').first()
   #print(user)
   #print(user.id,user.username)#输出查找到的用户名的id,密码等.
   
   #修改查询到的用户名的密码等
   #user = User.query.filter(User.username == 'mis1234').first()
   #user.password = '123'
   #db.session.commit()
   
   #再次插入一条记录
   #user = User(username = 'wkkkkkk',password = '123456', nickname='kk')
   #db.session.add(user)
   #db.session.commit()
   
   #删除一条记录
   #user = User.query.filter(User.username == 'mis1234').first()
   #db.session.delete(user)
   #db.session.commit()
   
   
   
   
   @app.route('/')
   def index():
       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('uname')
           passw = request.form.get('upass')
           user = User.query.filter(User.username==usern).first()
           if user:
               if user.password == passw:
                   session['user'] = usern;
                   return redirect(url_for('index'))
               else:
                   return 'password error!'
           else:
               return 'username is not exister!'
   
   
   
   @app.route('/register/',methods=['GET','POST'])
   def register():
       if request.method =='GET':
           return  render_template('register.html')
       else:
           usern = request.form.get('uname')
           teln = request.form.get('number')
           passw = request.form.get('upass')
           user = User.query.filter(User.username==usern).first()
           if user:
               return 'username existed'
           else:
               user1= User(username=usern,tel=teln,password=passw)
               db.session.add(user1)
               db.session.commit()
               return redirect(url_for('login'))
   
   
   @app.route('/question/',methods=['GET','POST'])
   def question():
       return render_template('question.html')
   
   if __name__ == '__main__':
       app.run(debug=True)

   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！";
           isError = false;
           return isError;
       }
       //window.alert("登录成功！")
       return isError;
   }

   #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)

   {% extends 'base.html' %}
       {% block title %}
           登录
       {% endblock %}
   {% block head %}
       <!--<title>login</title>-->
       <!--<link href="../static/css/login.css" rel="stylesheet" type="text/css">
       <script src="../static/js/login.js"></script>-->
        <link rel="stylesheet" type="text/css" href="{{ url_for('static',filename='css/login.css')}}">
       <script src="{{ url_for('static',filename='js/login.js') }}" type="text/javascript"></script>
   
   
   {%  endblock %}
   
   {% block main %}
         <div class="box">
             <h2>登录</h2>
             <form method="post" action="{{ url_for('login') }}">
             <div class="input_box">
                 username:<input id="uname" type="text" placeholder="请输入用户名" name="uname">
             </div>
             <div class="input_box">
                 password:<input id="upass" type="password" placeholder="请输入密码"  name="upass">
             </div>
             <div id="error_box" ><br></div>
             <div class="input_box">
                 <button id="button" onclick=" return fnLogin()">登录</button>&nbsp&nbsp&nbsp&nbsp&nbsp
                 <button id="button" onclick="window.location.replace({{ url_for("register") }})">注册</button>
             </div>
         </form>
         </div>
   {% endblock %}