java - 无法让我的 HashMap 在 jSTL 中工作

Question

我在 servlet 中有一个 Map

Map<String, Boolean> seatsModelComplete = new LinkedHashMap<>();

string 表示座位号，Boolean 表示座位是否已预订。

我在请求中设置属性如下:

request.setAttribute("seats", seatsModelComplete);

但我无法让它在 JSP 中工作。具体来说， map 不会被以下 foreach 循环

迭代

<c:forEach items="${requestScope.seats}" var="seats">
...
</c:forEach>

这是我的 Servlet:

@WebServlet(name = "SeatsServlet", urlPatterns = "/seats")

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

List<MovieDTO> movieDTOList = (List<MovieDTO>) request.getSession().getAttribute("movieDTOList");


int movie_id = Integer.parseInt(request.getParameter("movie_id"));

int hall_id = Integer.parseInt(request.getParameter("hall_id"));

int showtime_id = Integer.parseInt(request.getParameter("showtime_id"));

        MovieDTO selected_movie = null;

        Hall selected_hall = null;

        Showtime selected_showtime = null;
        for (MovieDTO m : movieDTOList) {
            if (m.getId() == movie_id) {
                selected_movie = m;
                break;
            }
        }
        if (selected_movie != null) {
            request.setAttribute("movie_title", selected_movie.getTitle());
        }

        for (Hall h : selected_movie.getHallList()) {
            if (h.getId() == hall_id) {
                selected_hall = h;
                break;
            }
        }
        if (selected_hall != null) {
            request.setAttribute("hall_id", selected_hall.getId());
        }

        for (Showtime s : selected_hall.getShowtimes()) {
            if (s.getId() == showtime_id) {
                selected_showtime = s;
                break;
            }
        }
        if (selected_showtime != null) {
            request.setAttribute("showtime_time", selected_showtime.getTime());
        }
        List<Seat> seats = selected_showtime.getSeats();


        int maxRows = (PropertyHolder.getInstance().getMaxRowsCount().toLowerCase().toCharArray()[0] - 'a') + 1;
        int maxNumbers = Integer.parseInt(PropertyHolder.getInstance().getMaxNumberCount());

        String aSeat;
        boolean isReserved;
        Map<String, Boolean> seatsModelComplete = new LinkedHashMap<>();
        for (int i = 0; i < maxRows; i++) {
            for (int j = 0; j < maxNumbers; j++) {
                aSeat = (((char)('A' + i)) + "").concat((j + 1) + "") ;
                isReserved = false;
                for (Seat seat : seats) {
                    if (seat.getRow().concat(seat.getNumber() + "").equals(aSeat)){
                        isReserved = true;
                    }
                }
                seatsModelComplete.put(aSeat, isReserved);
            }
        }
        request.setAttribute("seats", seatsModelComplete);
     // request.getSession().setAttribute("seats", seatsModelComplete); map gets passed only here, not in request scope

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

    }

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

Answer 1

你确定你初始化了吗？愚蠢的问题，但是呃...另外，你可以尝试类似的东西

<c:forEach items="${seats}" var="seat">
  <option value="${seat.key}">${seat.taken}</option
</c:forEach>

编辑:您可能将 jsp 搞砸了，您可以随时测试您的集合是否已正确初始化和/或是否可以在适当的范围内找到:

<c:choose>
    <c:when test="${empty seats}">
        Seats are empty or null.
    </c:when>
    <c:otherwise>
        Seats are not empty or null
    </c:otherwise>
</c:choose>