publicstaticvoidmain(String[] args) throwsSQLException {

    UserDao dao = newUserDao() ;

    List<User> ls = newArrayList<User>();

    ls = dao.query();

    for(inti=0; i<ls.size() ; i++){

        System.out.print("账号："+ls.get(i).getUsername()+" , ");

        System.out.println("密码："+ls.get(i).getPassword());

    }

}

以上代码我用JAVA运行能在控制台输出我数据库中的几个数据

publicvoiddoGet(HttpServletRequest request, HttpServletResponse response)

            throwsServletException, IOException {

    request.setCharacterEncoding("utf-8");

    UserDao dao = newUserDao() ;

    List<User> ls = newArrayList<User>();

    try{

        ls=dao.query();

    } catch(SQLException e) {

        // TODO Auto-generated catch block

        e.printStackTrace();

    }

    String name = request.getParameter("name");

    String password = request.getParameter("password");

    for(inti=0; i<ls.size() ; i++){

        if(ls.get(i).getUsername().equals(name) && ls.get(i).getPassword().equals(password)){

            request.getRequestDispatcher("/Success.jsp").forward(request,response);

        }  

        else{

            request.getRequestDispatcher("/Fail.jsp").forward(request,response);

        }

 

    }  

    

}

然后运行这个就报错了

我没用数据库的时候用if判断就能跳转页面

所以我感觉其他的代码应该没错 就把这部分粘出来了

String name = request.getParameter("name");

    String password = request.getParameter("password");

        if("a".equals(name) && "a".equals(password)){

            request.getRequestDispatcher("/Success.jsp").forward(request,response);

        }  

        else{

            request.getRequestDispatcher("/Fail.jsp").forward(request,response);

        }

}

上面代码是不用数据库就可以正常跳转 所以其他的代码应该没问题