大二期末 java web.用到数据库，jdbc.myeclipse实现用户的注册，登陆



并且不能出现500错误，用户不能重复注册。当用户任意点击时也不能出现500错误(At the end of sophomore year, Java web. is used in database, jdbc.myeclipse realizes user registration and landing.



And there is no 500 error. Users can't repeat registration. There is no 500 error when the user is clicking at random)