java - Servlet 在刷新时取消发布请求

Question

我有以下内容:

• JSP 页面向 Servlet 提交添加新客户的请求
• Servlet 使用一些 Action 类
• 重定向到其他一些 Jsp 页面

这是源代码。

new_customer.jsp:

<form action="/NewCustomerServlet" method="post">

  <input type="test" name="company_name" />
  <input type="submit" name="save_button" value="Save"/>

</form>

NewCustomerServlet:

@Override
protected void doPost(HttpServletRequest request, response) throws ServletException, IOException {
if(request.getParameter("save_button") != null){
    Customer customer;
    try {
        customer = action.createCustomer(request, response);
        request.setAttribute(Const.CUSTOMER, customer);
        RequestDispatcher dispatcher = request.getRequestDispatcher("index.jsp?v=v_cst");
        dispatcher.forward(request, response);
        return;
    } catch (InstantiationException | IllegalAccessException
                    | ClassNotFoundException | SQLException e) {
        e.printStackTrace();

        request.setAttribute(Const.ERR_MSG_ATTR_NAME, "Failed to insert new customer: " +
                             e.getMessage());
        RequestDispatcher dispatcher = request.getRequestDispatcher("CRM/index.jsp?v=n_cst");
        dispatcher.forward(request, response);
        return;
    }    
}

index.jsp:

<%
    if(request.getParameter("v").equals("v_cst")) {%>
        <jsp:include page="customer/view_customer.jsp"></jsp:include>
<%} %>

view_customer.jsp:

<%
    Customer customer = (Customer)request.getAttribute(Const.CUSTOMER);

    String customerId = "";
    String name = "";
    String phone = "";
    String website = "";
    String address = "";

    if(customer != null){

        customerId = customer.getCustomerId();
        name = customer.getName();
        phone = customer.getPhone();
        website = customer.getWebsite();
        address = customer.getAddress();
    }
%>
<table>
    <tr>
        <td>
            <label>Customer ID</label>
        </td>
        <td>
            <input type="text" name="customer_id" value="<%=customerId %>" />
        </td>
        <td>
            <input type="button" value="Search" onclick="javascript:searchCustomer"/>
        </td>
        <td>
            <label name="search_customer_err_msg" value="" style="color: red;"></label>
        </td>
    </tr>

    <tr>
        <td>
            <label>Customer Name</label>
        </td>
        <td>
            <input type="text" name="customer_name"  value="<%= name%>"/>
        </td>
    </tr>
    <tr>
        <td>
            <label>Customer website</label>
        </td>
        <td>
            <input type="text" name="customer_website" value="<%= website%>" />
        </td>
    </tr>

    <tr>
        <td>
            <label>Customer phone</label>
        </td>
        <td>
            <input type="text" name="customer_phone" value="<%= phone%>"/>
        </td>
    </tr>
    <tr>
        <td>
            <label>Customer Address</label>
        </td>
        <td>
            <input type="text" name="customer_address" value="<%= address%>"/>
        </td>
    </tr>
</table>

从页面 new_customer.jsp 添加新客户并在浏览器中查看页面 view_customer.jsp 后，如果我刷新页面(从我看到 view_customer.jsp 的页面)它将再次提交数据到servlet 并添加一个新客户，我将看到具有新客户 ID 的相同数据。

也许我还应该提一下，我在浏览器地址栏中看到的是 NewCustomerServlet 的 URL，而不是索引页面的 URL。

任何人都知道我在这里错过了什么以在刷新时再次取消帖子？

** 也许我忘了提到 new_customer.jsp 也包含在 index.jsp 页面中，也许这可能是这种行为的原因？

Answer 1

您不会重定向到 View ，您只是转发到相应的 JSP 服务器端，因此浏览器不会收到新 URL 的通知。

您必须构建重定向 URL 并执行 HttpServletResponse.sendRedirect，而不是使用 RequestDispatcher .这样，您的 servlet 会将 HTTP 重定向发送回客户端，客户端将调用相应的 URL 并相应地更改地址栏。

您可能不想重定向到 JSP 本身，而是重定向到另一个 Controller :

在 NewCustomerServlet 中:

@Override
protected void doPost(HttpServletRequest request, response) 
        throws ServletException, IOException {
    ...
    customer = action.createCustomer(request, response);
    response.sendRedirect("ShowCustomer?customerId=" + customer.getCustomerId());
    ...

ShowCustomerServlet 可能如下所示:

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

    // get customer by HTTP Request Parameter 'customerId'
    customer = action.getCustomer(request, response);

    // set attribute and forward to JSP
    request.setAttribute(Const.CUSTOMER, customer);
    RequestDispatcher dispatcher = request.getRequestDispatcher("showCustomer.jsp");
    dispatcher.forward(request, response);
    ...