根據Servlet的請求轉發相同的URL，因此再次重復操作

Question

我一直在嘗試使我的項目更加結構化，因此我一直在遵循https://netbeans.org/kb/docs/javaee/ecommerce/page-views-controller.html#controller中的netbeans電子商務示例項目中的示例。 我根據示例更改了控制器。 現在，我無法進入在數據庫中顯示值的頁面。

我的Servlet如下。

protected void processRequest(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    response.setContentType("text/html;charset=UTF-8");
    Op_Stock ops = new Op_Stock();
    String userPath = request.getServletPath();
    String param = null;
    Map<String, String> prdMap = new LinkedHashMap<String, String>();
    Map<String, String> lvlMap = new LinkedHashMap<String, String>();
    ArrayList<HashMap<String, String>> stkList = new ArrayList<>();
    switch (userPath) {
        case "/ViewStock":
            stkList = ops.getAllStockDetails();
            request.setAttribute("stkList", stkList);
            userPath = "Stock.jsp";
            param = "type=m&page=stk";
            break;
        case "/AddStockForm":
            prdMap = ops.getAllProducts();
            lvlMap = ops.getAllLevels();
            request.setAttribute("prdMap", prdMap);
            request.setAttribute("lvlMap", lvlMap);
            userPath = "Insertstk.jsp";
            param = "type=m&page=stk";
            break;
        case "/AddStock":
            System.out.println("prdId: " + request.getParameter("prdId"));
            int iprdId = Integer.parseInt(request.getParameter("prdId"));
            int istkIn = Integer.parseInt(request.getParameter("stkIn"));
            int istkthld = Integer.parseInt(request.getParameter("stkthld"));
            int ilvlId = Integer.parseInt(request.getParameter("lvlId"));
            int stkIn = ops.insertStockDetails(iprdId, istkIn, istkthld, ilvlId);
            stkList = ops.getAllStockDetails();
            request.setAttribute("stkList", stkList);
            if (stkIn > 0) {
                userPath = "/Stock.jsp";
                param = "message=Stock Details Created!&pg=stk&type=m";
            } else {
                prdMap = ops.getAllProducts();
                lvlMap = ops.getAllLevels();
                request.setAttribute("prdMap", prdMap);
                request.setAttribute("lvlMap", lvlMap);
                userPath = "/Insertstk.jsp";
                param = "message=Could not create!&pg=stk&type=m";
            }
            break;
        case "/DeleteStock":
            int delStk = ops.deleteStockDetails(request.getParameter("stkId"));
            if (delStk > 0) {
                userPath = "Stock.jsp";
                param = "message=Stock Details Deleted!&pg=stk&type=m";
                stkList = ops.getAllStockDetails();
                request.setAttribute("stkList", stkList);
            } else {
                userPath = "Stock.jsp";
                stkList = ops.getAllStockDetails();
                request.setAttribute("stkList", stkList);
                param = "message=Could not delete!&pg=stk&type=m";
            }
            break;
    }

    // use RequestDispatcher to forward request internally
    String url = userPath + "?" + param;
    request.getRequestDispatcher(url).forward(request, response);
    //response.sendRedirect(url);

}

在servlet中，我將屬性設置為存儲數據庫內容的請求。

假設我正在執行一個插入操作，該操作在切換用例“ / AddStock”中執行此操作之后，該請求被轉發到顯示該表的頁面，因為我正在使用它，因此它將轉到顯示頁面，但URL地址欄中的會與插入表單中的所有請求參數保持不變，因此，當我刷新頁面時，插入操作將再次發生。 如果我使用response.sendRedirect（url），則將無法使用請求屬性，因此將無法顯示數據庫值。

我的插入表格如下。

<div class="col-md-10">
                    <form method="POST" action="AddStock" class="form-horizontal">
                        <div class="form-group">
                            <label class="col-sm-2 control-label">Product</label>
                            <div class="col-sm-4">                                    
                                <select id="s_prdname" class="form-control" name="prdId" required>
                                    <option>Select</option>
                                    <c:forEach items="${prdList}" var="mapItem">
                                        <option value="${mapItem.key}">${mapItem.value}</option>
                                    </c:forEach> 
                                </select>
                            </div>
                        </div>
                        <div class="form-group">
                            <label class="col-sm-2 control-label">Level</label>
                            <div class="col-sm-4">                                    
                                <select id="s_lvlname" class="form-control" name="lvlId" required>
                                    <option>Select</option>
                                    <c:forEach items="${lvlList}" var="mapItem">
                                        <option value="${mapItem.key}">${mapItem.value}</option>
                                    </c:forEach> 
                                </select>
                            </div>
                        </div>
                        <div class="form-group">
                            <label class="col-sm-2 control-label">In-Stock</label>
                            <div class="col-sm-2">
                                <input type="number" name="stkIn" class="form-control" id="stkIn"/>
                            </div>
                        </div>
                        <div class="form-group">
                            <label class="col-sm-2 control-label">Threshold</label>
                            <div class="col-sm-2">
                                <input type="number" name="stkthld" class="form-control" id="stkthld"/>
                            </div>
                        </div>
                        <div class="form-group">
                            <div class="col-sm-offset-2 col-sm-10">
                                <button type="submit" class="btn btn-default btn-primary"><strong>Submit</strong></button>
                            </div>
                        </div>
                    </form>
                </div> 

我的顯示頁面如下。

<div class="table-responsive">
                    <table class="table table-bordered table-striped table-hover">
                        <thead>
                        <th><strong>Product Name</strong></th>
                        <th><strong>Level</strong></th>
                        <th><strong>In Stock</strong></th>
                        <th><strong>Threshold</strong></th>
                        <th><strong>Expiry</strong></th>
                        <th><strong>Operations</strong></th>
                        </thead>                            
                        <tbody>
                            <jsp:useBean id="lvl" scope="request" class="Level.Level"/>
                            <jsp:useBean id="prd" scope="request" class="Product.Product"/>
                            <c:forEach items="${stkList}" var="row">
                                <tr>
                                    <td><jsp:setProperty name="prd" property="prdId" value="${row.prdStk}"/><jsp:getProperty name="prd" property="prdName"/></td>
                                    <td><jsp:setProperty name="lvl" property="lvlId" value="${row.lvlStk}"/><jsp:getProperty name="lvl" property="lvlName"/></td>
                                    <td>${row.inStk}</td>
                                    <td>${row.thldStk}</td>
                                    <td>${row.expStk}</td>
                                    <td>
                                        <button type="button" class="btn btn-default btn-sm btn-danger" onclick="deletedata('${row.idStk}');">
                                            <span class="glyphicon glyphicon-trash"></span>
                                        </button>                                            
                                        <button class="btn btn-info btn-sm" data-toggle="modal" data-target="#myModal">
                                            <span class="glyphicon glyphicon-eye-open"></span>
                                        </button>                                    
                                    </td>
                                </tr>
                            </c:forEach>
                        </tbody>
                        <tfoot>
                        <td></td>
                        <td></td>
                        <td></td>
                        <td></td>
                        <td></td>
                        <td></td>
                        </tfoot>
                    </table>
                </div>

請幫助我解決此問題，如果我使用的方法錯誤，請提出正確的建議。

Answer 1

為了解決這個問題，我用了。

response.sendRedirect(url);

代替

request.getRequestDispatcher(url).forward(request, response);

而且，我沒有通過在request中設置屬性來在DB中顯示值，而是使用了如下所示的訪問類中的方法的方法。

<jsp:useBean id="stk" scope="request" class="Stock.Op_Stock"/>
<c:forEach items="${stk.allStockDetails}" var="row">
    // Values in the map displayed here
</c:forEach>