Javaservlet切换执行顺序

我在使用servlet中的两个开关时遇到了一些问题。我试图从jsp上的这些开关加载数据，但它基本上只在第一个开关上加载，第二个开关没有执行。我尝试只创建一个开关，但它会给我一些错误，如提交响应后无法转发等。你们知道解决这个问题的正确方法吗？ 谢谢

代码如下：

public class UserControllerServlet extends HttpServlet {

    private static final long serialVersionUID = 1L;

    private UserDao userDao;
    private ReservationDao reservationDao;
    private DBConnection dbConnection;


    @Override
    public void init() throws ServletException {
        super.init();

        try {
            userDao = new UserDao(dbConnection);
            reservationDao = new ReservationDao(dbConnection);
        }catch(Exception e) {
            throw new ServletException(e);
        }
    }




    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException 
    {

        try {
            // read the "command" parameter
            String theCommand = request.getParameter("command");
            String theCommand2 = request.getParameter("command2");
            if(theCommand == null) {
                theCommand = "LIST";
            }

            if(theCommand2 == null) {
                theCommand2 = "LIST";
            }

            switch(theCommand2) {
            case "LIST":
                listReservations(request, response);
                return;

            case "ADD":
                addReservation(request, response);
                return;


            case "LOAD":
                loadReservation(request, response);
                return;


            case "UPDATE":
                updateReservation(request, response);
                return;



            case "DELETE":
                deleteReservation(request, response);
                return;


            default:
                listReservations(request, response);
        }

            //route to the appropriate method
            switch(theCommand) {
                case "LIST":
                    listUsers(request, response);
                    break;

                case "ADD":
                    addUser(request, response);
                    break;


                case "LOAD":
                    loadUser(request, response);
                    break;


                case "UPDATE":
                    updateUser(request, response);
                    break;



                case "DELETE":
                    deleteUser(request, response);
                    break;


                default:
                    listUsers(request, response);
            }

        }catch(Exception e) {
            throw new ServletException(e);
        }

    }

    private void deleteUser(HttpServletRequest request, HttpServletResponse response) 
    throws Exception {
        String theUserId = request.getParameter("userId");

        userDao.deleteUser(theUserId);

        listUsers(request, response);
    }

    private void updateUser(HttpServletRequest request, HttpServletResponse response) 
            throws Exception {

        int id = Integer.parseInt(request.getParameter("userId"));
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        String role = request.getParameter("role");
        String nume = request.getParameter("nume");
        String prenume = request.getParameter("prenume");
        String email = request.getParameter("email");
        String adresa = request.getParameter("adresa");
        UserBean theUser = new UserBean(id, username, password, role,nume,prenume,email,adresa);
        userDao.updateUser(theUser);
        listUsers(request, response);
    }

    private void loadUser(HttpServletRequest request, HttpServletResponse response) throws Exception {
        String theUserId = request.getParameter("userId");
        UserBean theUser = userDao.getUser(theUserId);
        request.setAttribute("THE_USER", theUser);
        RequestDispatcher dispatcher = 
                request.getRequestDispatcher("/update-user-form.jsp");
        dispatcher.forward(request, response);
        return;
    }

    private void addUser(HttpServletRequest request, HttpServletResponse response) throws Exception {

        String username = request.getParameter("username");
        String password = request.getParameter("password");
        String role = request.getParameter("role");
        String nume = request.getParameter("nume");
        String prenume = request.getParameter("prenume");
        String email = request.getParameter("email");
        String adresa = request.getParameter("adresa");
        UserBean theUser = new UserBean(username, password, role,nume,prenume,email,adresa);
        userDao.addUser(theUser);
        listUsers(request, response);

    }

    private void listUsers(HttpServletRequest request, HttpServletResponse response) 
    throws Exception {
        List<UserBean> users = userDao.getUsers();
        request.setAttribute("USER_LIST", users);
        RequestDispatcher dispatcher = request.getRequestDispatcher("/list-users.jsp");
        dispatcher.forward(request, response);
        return;
    }


    //Reservations Methods

    private void deleteReservation(HttpServletRequest request, HttpServletResponse response) 
            throws Exception {
                String theReservationId = request.getParameter("reservationId");
                reservationDao.deleteReservation(theReservationId);
                listReservations(request, response);
            }

            private void updateReservation(HttpServletRequest request, HttpServletResponse response) 
                    throws Exception {

                int idReservation = Integer.parseInt(request.getParameter("reservationId"));
                int idUser = Integer.parseInt(request.getParameter("userId"));
                String dataCheckin = request.getParameter("dataCheckin");
                String dataCheckout = request.getParameter("dataCheckout");
                int nrPersoane = Integer.parseInt(request.getParameter("nrPersoane"));
                int nrCamere = Integer.parseInt(request.getParameter("nrCamere"));
                ReservationBean theReservation = new ReservationBean(idReservation, idUser, dataCheckin, dataCheckout,nrPersoane,nrCamere);
                reservationDao.updateReservation(theReservation);
                listReservations(request, response);
            }

            private void loadReservation(HttpServletRequest request, HttpServletResponse response) throws Exception {
                String theReservationId = request.getParameter("reservationId");
                ReservationBean theReservation = reservationDao.getReservation(theReservationId);
                request.setAttribute("THE_RESERVATION", theReservation);
                RequestDispatcher dispatcher = 
                        request.getRequestDispatcher("/update-reservation-form.jsp");
                dispatcher.forward(request, response);
                return;
            }

            private void addReservation(HttpServletRequest request, HttpServletResponse response) throws Exception {

                int userId = Integer.parseInt(request.getParameter("userId"));
                String dataCheckin = request.getParameter("dataCheckin");
                String dataCheckout = request.getParameter("dataCheckout");
                int nrPersoane = Integer.parseInt(request.getParameter("nrPersoane"));
                int nrCamere = Integer.parseInt(request.getParameter("nrCamere"));
                ReservationBean theReservation = new ReservationBean(userId, dataCheckin, dataCheckout,nrPersoane,nrCamere);
                reservationDao.addReservation(theReservation);
                listReservations(request, response);

            }

            private void listReservations(HttpServletRequest request, HttpServletResponse response) 
                throws Exception {
                    List<ReservationBean> reservations = reservationDao.getReservations();
                    request.setAttribute("RESERVATION_LIST", reservations);
                     request.getRequestDispatcher("/list-users.jsp").forward(request, response);
                    return;
                }


    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

}

公共类UserControllerServlet扩展了HttpServlet{
私有静态最终长serialVersionUID=1L；
私有UserDao UserDao；
私人预订道预订道；
专用数据库连接数据库连接；
@凌驾
public void init（）引发ServletException{
super.init（）；
试一试{
userDao=新的userDao（dbConnection）；
reservationDao=新的reservationDao（dbConnection）；
}捕获（例外e）{
抛出新的ServletException（e）；
}
}
受保护的void doGet（HttpServletRequest请求，HttpServletResponse响应）抛出ServletException，IOException
{
试一试{
//读取“command”参数
字符串theCommand=request.getParameter（“命令”）；
字符串command2=request.getParameter（“command2”）；
if（命令==null）{
命令=“列表”；
}
if（命令2==null）{
命令2=“列表”；
}
开关（命令2）{
案例“列表”：
列表保留（请求、响应）；
返回；
案例“添加”：
添加预订（请求、响应）；
返回；
案例“荷载”：
loadReservation（请求、响应）；
返回；
案例“更新”：
更新服务（请求、响应）；
返回；
案例“删除”：
删除保留（请求、响应）；
返回；
违约：
列表保留（请求、响应）；
}
//路由到适当的方法
开关（命令）{
案例“列表”：
列表用户（请求、响应）；
打破
案例“添加”：
addUser（请求、响应）；
打破
案例“荷载”：
loadUser（请求、响应）；
打破
案例“更新”：
updateUser（请求、响应）；
打破
案例“删除”：
删除用户（请求、响应）；
打破
违约：
列表用户（请求、响应）；
}
}捕获（例外e）{
抛出新的ServletException（e）；
}
}
私有void deleteUser（HttpServletRequest请求，HttpServletResponse响应）
抛出异常{
字符串theUserId=request.getParameter（“userId”）；
userDao.deleteUser（userid）；
列表用户（请求、响应）；
}
私有void updateUser（HttpServletRequest请求，HttpServletResponse响应）
抛出异常{
intid=Integer.parseInt（request.getParameter（“userId”）；
字符串username=request.getParameter（“用户名”）；
字符串密码=request.getParameter（“密码”）；
字符串角色=request.getParameter（“角色”）；
字符串nume=request.getParameter（“nume”）；
字符串prenume=request.getParameter（“prenume”）；
字符串email=request.getParameter（“email”）；
字符串adresa=request.getParameter（“adresa”）；
UserBean theUser=newuserbean（id、用户名、密码、角色、nume、prenume、电子邮件、地址）；
userDao.updateUser（用户）；
列表用户（请求、响应）；
}
私有void loadUser（HttpServletRequest请求、HttpServletResponse响应）引发异常{
字符串theUserId=request.getParameter（“userId”）；
UserBean theUser=userDao.getUser（theUserId）；
setAttribute（“用户”，theUser）；
RequestDispatcher=
getRequestDispatcher（“/update user form.jsp”）；
转发（请求、响应）；
返回；
}
私有void addUser（HttpServletRequest请求、HttpServletResponse响应）引发异常{
字符串username=request.getParameter（“用户名”）；
字符串密码=request.getParameter（“密码”）；
字符串角色=request.getParameter（“角色”）；
字符串nume=request.getParameter（“nume”）；
字符串prenume=request.getParameter（“prenume”）；
字符串email=request.getParameter（“email”）；
字符串adresa=request.getParameter（“adresa”）；
UserBean theUser=newuserbean（用户名、密码、角色、nume、prenume、电子邮件、地址）；
userDao.addUser（theUser）；
列表用户（请求、响应）；
}
私有void列表用户（HttpServletRequest请求、HttpServletResponse响应）
抛出异常{
List users=userDao.getUsers（）；
setAttribute（“用户列表”，用户）；
RequestDispatcher=request.getRequestDispatcher（“/list users.jsp”）；
转发（请求、响应）；
返回；
}
//保留方法
私有void deleteReservation（HttpServletRequest请求、HttpServletResponse响应）
抛出异常{
字符串theReservationId=request.getParameter（“reservationId”）；
reservationDao.deleteReservation（theReservationId）；
列表保留（请求、响应）；
}
私有void updateReservation（HttpServletRequest请求，HttpServletResponse响应）
抛出异常{
int idReservation=Integer.parseInt（request.getParameter（“reservationId”）；
switch(theCommand2) {
case "LIST":
    listReservations(request, response);
    break; // not return.
case "ADD":
    addReservation(request, response);
    break; // not return..
// ...