anchor.diff:  ///
   responseStuSignUp(request) async{
     //todo
  -  request.readAsString().then(insertDataBaseStu);
  +  var responseDBText=await request.readAsString().then(insertDataBaseStu);
     //
  +  print(responseDBText);
     return (new Response.ok('success!',headers: _headers));
   }
   insertDataBaseStu(data) async{
     String username;
     String userClass;
     String password;
  +  String responseText;
     Map realdata=JSON.decode(data);
     username=realdata['Username'];
     userClass=realdata['Class'];
  
positive.code:   //todo 将数据存入数据库
    var pool=new ConnectionPool(host:'localhost',port:3306,user:'root',db:'vocabulary',max:5);
    var query=await pool.prepare('insert into userinfo(Username,Password,Class,Status) values(?,?,?,?)');
    var result=await query.execute([username,password,userClass,'stu']);
  }
  
  responseTeaSignUp(request) async{
    //todo 将教师的注册信息写入数据库
    request.readAsString().then(insertDataBaseTea);
    //
    return (new Response.ok('success!',headers: _headers));
  }
  
  
negative.code:   var pool=new ConnectionPool(host:'localhost',port:3306,user:'root',db:'vocabulary',max:5);
    var query=await pool.prepare('insert into userinfo(Username,Password,Class,Status) values(?,?,?,?)');
    var result=await query.execute([username,password,userClass,'tea']);
    print('${result.insertId}');//如果插入成功，这会是0，否则会报错
  }
  
  
  