validation - 如何以良好的格式打印/显示错误？

Question

我目前正在 java eclipse IDE 上做一个项目。我有一个如下所示的具有密码更改功能的 servlet。如您所见，我已将其编程为根据用户输入返回各种错误，例如“密码不匹配”。但是，这始终打印在屏幕顶部。有什么方法可以将这些错误输出为实际的格式错误吗？也许以弹出框的形式或者至少将其放置在适当的位置？

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.sql.*;

public class NewPassword extends HttpServlet { 
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

                response.setContentType("text/html;charset=UTF-8");
                PrintWriter out = response.getWriter();

                String oldpassword = request.getParameter("oldpassword"); 
                String newpassword = request.getParameter("newpassword"); 
                String confirmpassword = request.getParameter("confirmpassword"); 

                int newpass = newpassword.length(); 

                HttpSession session = request.getSession(false);
                String employeeid = ""; 

                if(session != null) { 
                    employeeid = (String)session.getAttribute("employeeid"); 
                }

                boolean st = false; 
                try { 
                    Class.forName("com.mysql.jdbc.Driver").newInstance(); 
                    Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/payroll_system", "root", ""); 
                    PreparedStatement ps = con.prepareStatement("SELECT pwd FROM payroll_system.employee_login WHERE employeeID = ?");
                    ps.setString(1, employeeid);
                    ResultSet rs = ps.executeQuery(); 
                    st = rs.next(); 
                    String currentpassword = rs.getString("pwd"); 
                    if(st) { 

                        if((currentpassword.equals(oldpassword)) && newpassword.equals(confirmpassword) && newpass >= 8) { 
                            PreparedStatement pd = con.prepareStatement("UPDATE payroll_system.employee_login SET pwd = ? where employeeID = ?" ); 
                            pd.setString(1, newpassword);
                            pd.setString(2, employeeid);
                            int updated = pd.executeUpdate(); 
                            if(updated > 0){
                                out.println("Password Successfully Updated");
                                RequestDispatcher rd = request.getRequestDispatcher("changePassAdmin.html");
                                rd.include(request, response);
                            }
                        }

                        else if(oldpassword.equals("") || newpassword.equals("")  || confirmpassword.equals("") ) { 
                            out.println("Fields cannot be left blank.");
                            RequestDispatcher rd = request.getRequestDispatcher("changePassAdmin.html");
                            rd.include(request, response);
                        }
                        else if(!currentpassword.equals(oldpassword) && !newpassword.equals(confirmpassword)) { 
                            out.println("Old password is incorrect and passwords do not match, please try again.");
                            RequestDispatcher rd = request.getRequestDispatcher("changePassAdmin.html"); 
                            rd.include(request, response); 
                        }
                        else if(!currentpassword.equals(oldpassword)) { 
                            out.println("Old password entered incorrectly, please try again.");
                            RequestDispatcher rd = request.getRequestDispatcher("changePassAdmin.html");
                            rd.include(request, response);
                        }
                        else if(!newpassword.equals(confirmpassword)) { 
                            out.println("Passwords do not match, please try again.");
                            RequestDispatcher rd = request.getRequestDispatcher("changePassAdmin.html");
                            rd.include(request, response);
                        }
                        else if(newpass < 8 ) {
                            out.println("New Password must be atleast 8 characters in length.");
                            RequestDispatcher rd = request.getRequestDispatcher("changePassAdmin.html");
                            rd.include(request, response);
                        }



                    }
                }catch(Exception e)
                 {
                     e.printStackTrace();
                 }
               out.close();
       }
   }

Answer 1

您可以使用ajax和js来处理错误。使用ajax与服务器通信，当出现错误时，使用js函数显示对话框。这只是一个解决方案。您可以尝试一下。