错误提交后以表单保存数据（JSP/Java）

如何防止jsp表单重置？我有一个将数据传递给servlet的jsp表单。如果用户在未填写所有字段的情况下按“提交”，则会显示一条错误消息，邀请用户填写表单的所有字段。问题在于，当出现错误消息时，用户在表单中输入的数据将被清除。如何确保保存此数据，并且用户不必再次重写所有内容

我的意思是，它必须是一种允许我保持表单填写的方法，因为它必须工作，即使，例如，所有字段都已填写，并且电子邮件字段没有@符号

这是我的jsp：

新康塔托酒店

Id:

名称：

Cognome:

安妮：

Sesso:

英迪里佐：

电话号码：

电子邮件：



错误
注意！这是一张100美元的邮票




错误
注意！我想我应该在这里
在数据库中演示。谢丽尔没有这样做




错误
注意！valore与“sesso”puòessere solo“m”组合，
“M”、“f”、“f”




错误
注意！电视台的数字是一个人的数字




错误
注意！L'email deve contenre il simbolo'@'




错误
注意！从德沃诺-埃塞尔编译而来的课程




阿吉恩托·努沃·康塔托！

身份证件：

Nome：

Cognome：

等等：

Sesso：

英迪里佐：
电话号码：

电子邮件：

这是我的servlet：

/**
 * @see HttpServlet#HttpServlet()
 */
public AggiungiPersona() {
    super();
    // TODO Auto-generated constructor stub
}

/**
 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
 *      response)
 */
protected void doPost(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    
    
    // verifica se esiste una sessione già creata
            // se no: reindirizzo l'utente in login.html
            HttpSession session = request.getSession(false);
            
            if(session == null || session.getAttribute("loggedIn")==null || !session.getAttribute("loggedIn").equals(true)) {
               response.sendRedirect("login.jsp");
               
                return;
            }
            
            

    // prendo tutte le persone dal db e le metto in arrayList per poterci ciclare
    // sopra e controllare se l'id inserito esiste gia nella collezione

    ArrayList<Persona> listaPersone = null;
    listaPersone = PersonaQuery.getPersone();

    boolean found = false;

    if (request.getParameter("id") == "" || request.getParameter("nome") == ""
            || request.getParameter("cognome") == "" || request.getParameter("anni") == ""
            || request.getParameter("sesso") == "" || request.getParameter("indirizzo") == ""
            || request.getParameter("numTel") == "" || request.getParameter("email") == ""

    ) {
        request.setAttribute("error6", true);

        RequestDispatcher view = request.getRequestDispatcher("aggiungiPersona.jsp");
        view.forward(request, response);

    } else if ((Integer.parseInt(request.getParameter("anni")) < 0)
            || (Integer.parseInt(request.getParameter("anni")) > 100)) {
        request.setAttribute("error", true);

        RequestDispatcher view = request.getRequestDispatcher("aggiungiPersona.jsp");
        view.forward(request, response);

    } else if ((request.getParameter("sesso").charAt(0) != 'm') && (request.getParameter("sesso").charAt(0) != 'M')
            && (request.getParameter("sesso").charAt(0) != 'f')
            && (request.getParameter("sesso").charAt(0) != 'F')) {
        request.setAttribute("error3", true);
        RequestDispatcher view = request.getRequestDispatcher("aggiungiPersona.jsp");
        view.forward(request, response);
    } else if (Pattern.matches("^[0-9]*$", request.getParameter("numTel")) == false) {
        request.setAttribute("error4", true);
        RequestDispatcher view = request.getRequestDispatcher("aggiungiPersona.jsp");
        view.forward(request, response);
    } else if (!request.getParameter("email").contains("@")) {
        request.setAttribute("error5", true);
        RequestDispatcher view = request.getRequestDispatcher("aggiungiPersona.jsp");
        view.forward(request, response);

    } else {
        for (Persona persona : listaPersone) {

            if (Integer.parseInt(request.getParameter("id")) == persona.getId()) {

                found = true;

                request.setAttribute("error2", true);
                RequestDispatcher view = request.getRequestDispatcher("aggiungiPersona.jsp");
                view.forward(request, response);

            }
        }
        if (!found) {
            try {
                PersonaQuery.aggiungiPersona(Integer.parseInt(request.getParameter("id")),
                        request.getParameter("nome"), request.getParameter("cognome"),
                        Integer.parseInt(request.getParameter("anni")), request.getParameter("sesso"),
                        request.getParameter("indirizzo"), request.getParameter("numTel"),
                        request.getParameter("email"));

            } catch (Exception e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            request.setAttribute("successo", true);
            RequestDispatcher view = request.getRequestDispatcher("aggiungiPersona.jsp");
            view.forward(request, response);
        }

    }

}

/**
*@参见HttpServlet#HttpServlet（）
*/
公共aggiungiperona（）{
超级（）；
//TODO自动生成的构造函数存根
}
/**
*@参见HttpServlet#doPost（HttpServletRequest，HttpServletResponse
*（答复）
*/
受保护的void doPost（HttpServletRequest请求、HttpServletResponse响应）
抛出ServletException、IOException{
//验证您是否可以创建一个会话
//se编号：login.html中的reindirizzo l'utente
HttpSession session=request.getSession（false）；
如果（session==null | | | session.getAttribute（“loggedIn”）==null | | |！session.getAttribute（“loggedIn”）.equals（true））{
sendRedirect（“login.jsp”）；
返回；
}
//根据poterci ciclare的arrayList中的个人资料
//女高音和女低音控制音
ArrayList listaPersone=null；
listaPersone=personalquery.getPersone（）；
布尔值=false；
if（request.getParameter（“id”）=“”| | request.getParameter（“nome”）=“”
||request.getParameter（“cognome”）==“| | request.getParameter（“anni”）==”“
||request.getParameter（“sesso”）=“request.getParameter（“indirizzo”）=”“”
||request.getParameter（“numTel”）==“|| request.getParameter（“email”）==”
) {
setAttribute（“error6”，true）；
RequestDispatcher视图=request.getRequestDispatcher（“aggiungiperona.jsp”）；
视图。转发（请求、响应）；
}else if（（Integer.parseInt（request.getParameter（“anni”））<0）
||（Integer.parseInt（request.getParameter（“anni”））>100））{
setAttribute（“错误”，true）；
RequestDispatcher视图=request.getRequestDispatcher（“aggiungiperona.jsp”）；
视图。转发（请求、响应）；
}else if（（request.getParameter（“sesso”）.charAt（0）！='m'）&（request.getParameter（“sesso”）.charAt（0）！='m'））
&&（request.getParameter（“sesso”）.charAt（0）！=“f”）
&&（request.getParameter（“sesso”）.charAt（0）！='F'））{
setAttribute（“error3”，true）；
RequestDispatcher视图=request.getRequestDispatcher（“aggiungiperona.jsp”）；
视图。转发（请求、响应）；
}else if（Pattern.matches（“^[0-9]*$”，request.getParameter（“numTel”））==false）{
setAttribute（“error4”，true）；
RequestDispatcher视图=request.getRequestDispatcher（“aggiungiperona.jsp”）；
视图。转发（请求、响应）；
}如果（！request.getParameter（“电子邮件”）包含（“@”），则为else{
setAttribute（“error5”，true）；
RequestDispatcher视图=request.getRequestDispatcher（“aggiungiperona.jsp”）；
视图。转发（请求、响应）；
}否则{
for（Persona Persona:listaPersone）{
if（Integer.parseInt（request.getParameter（“id”））==persona.getId（））{
发现=真；
setAttribute（“error2”，true）；
RequestDispatcher视图=request.getRequestDispatcher（“aggiungiperona.jsp”）；
视图。转发（请求、响应）；
}
}
如果（！找到）{
试一试{
PersonaQuery.aggiungiPersona（Integer.parseInt（request.getParameter（“id”）），
request.getParameter（“nome”）、request.getParameter（“cognome”），
Integer.parseInt（request.getParameter（“anni”）），request.getParameter（“sesso”），
request.getParameter（“indirizzo”）、request.getParameter（“numTel”），
request.getParameter（“电子邮件”）；
}捕获（例外e）{
//TODO自动生成的捕捉块
/**
 * @see HttpServlet#HttpServlet()
 */
public AggiungiPersona() {
    super();
    // TODO Auto-generated constructor stub
}

/**
 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
 *      response)
 */
protected void doPost(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    
    
    // verifica se esiste una sessione già creata
            // se no: reindirizzo l'utente in login.html
            HttpSession session = request.getSession(false);
            
            if(session == null || session.getAttribute("loggedIn")==null || !session.getAttribute("loggedIn").equals(true)) {
               response.sendRedirect("login.jsp");
               
                return;
            }
            
            

    // prendo tutte le persone dal db e le metto in arrayList per poterci ciclare
    // sopra e controllare se l'id inserito esiste gia nella collezione

    ArrayList<Persona> listaPersone = null;
    listaPersone = PersonaQuery.getPersone();

    boolean found = false;

    if (request.getParameter("id") == "" || request.getParameter("nome") == ""
            || request.getParameter("cognome") == "" || request.getParameter("anni") == ""
            || request.getParameter("sesso") == "" || request.getParameter("indirizzo") == ""
            || request.getParameter("numTel") == "" || request.getParameter("email") == ""

    ) {
        request.setAttribute("error6", true);

        RequestDispatcher view = request.getRequestDispatcher("aggiungiPersona.jsp");
        view.forward(request, response);

    } else if ((Integer.parseInt(request.getParameter("anni")) < 0)
            || (Integer.parseInt(request.getParameter("anni")) > 100)) {
        request.setAttribute("error", true);

        RequestDispatcher view = request.getRequestDispatcher("aggiungiPersona.jsp");
        view.forward(request, response);

    } else if ((request.getParameter("sesso").charAt(0) != 'm') && (request.getParameter("sesso").charAt(0) != 'M')
            && (request.getParameter("sesso").charAt(0) != 'f')
            && (request.getParameter("sesso").charAt(0) != 'F')) {
        request.setAttribute("error3", true);
        RequestDispatcher view = request.getRequestDispatcher("aggiungiPersona.jsp");
        view.forward(request, response);
    } else if (Pattern.matches("^[0-9]*$", request.getParameter("numTel")) == false) {
        request.setAttribute("error4", true);
        RequestDispatcher view = request.getRequestDispatcher("aggiungiPersona.jsp");
        view.forward(request, response);
    } else if (!request.getParameter("email").contains("@")) {
        request.setAttribute("error5", true);
        RequestDispatcher view = request.getRequestDispatcher("aggiungiPersona.jsp");
        view.forward(request, response);

    } else {
        for (Persona persona : listaPersone) {

            if (Integer.parseInt(request.getParameter("id")) == persona.getId()) {

                found = true;

                request.setAttribute("error2", true);
                RequestDispatcher view = request.getRequestDispatcher("aggiungiPersona.jsp");
                view.forward(request, response);

            }
        }
        if (!found) {
            try {
                PersonaQuery.aggiungiPersona(Integer.parseInt(request.getParameter("id")),
                        request.getParameter("nome"), request.getParameter("cognome"),
                        Integer.parseInt(request.getParameter("anni")), request.getParameter("sesso"),
                        request.getParameter("indirizzo"), request.getParameter("numTel"),
                        request.getParameter("email"));

            } catch (Exception e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            request.setAttribute("successo", true);
            RequestDispatcher view = request.getRequestDispatcher("aggiungiPersona.jsp");
            view.forward(request, response);
        }

    }

}