有条件地使用 RequestDispatcher 跨多个 JSP 页面发送同一个 Java 对象

Question

请多多包涵，因为我对 JSP 很陌生。我提前感谢您的帮助；非常感谢。

背景

我正在尝试构建一个 Web 应用程序，它可以在整个用户的登录会话中“记住”某些 java 对象。目前，我有一个 servlet，它使用 RequestDispatcher 通过其 doPost 方法将对象发送到 JSP 页面。

这里是 servlet 的 doPost：

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

    String strBook = "Test Book";

    // Send strBook to the next jsp page for rendering
    request.setAttribute("book", strBook);
    RequestDispatcher dispatcher = request.getRequestDispatcher("sample.jsp");
    dispatcher.include(request, response);

}

sample.jsp 获取 strBook 对象，并对其进行处理。 sample.jsp 的主体如下所示：

<body>

<% 
    // Obtain strBook for rendering on current page
    String strBook = (String) request.getAttribute("book"); 

    /*
      // TODO: A way to conditionally call code below, when form is submitted 
      // in order for sample2.jsp to have strBook object.

      RequestDispatcher dispatcher = request.getRequestDispatcher("sample2.jsp");
      dispatcher.include(request, response);
    */

%>


<h1> Book: </h1>
<p> <%=strBook%> </p>

<form action="sample2.jsp"  method="post">
    <input type="submit" id="buttonSubmit" name="buttonSubmit" value="Buy"/>
</form>

</body>

问题

如何从 sample.jsp 中获取 strBook 对象，并将其发送到 sample2.jsp当点击提交按钮时（这样 strBook 对象可以在 sample2.jsp 中使用）？

目前sample2.jsp的body是这样的，里面的strBook为null：

<body>

<% 
    // Obtain strBook for rendering on current page
    String strBook = (String) request.getAttribute("book"); 
%>


<h1> Book: </h1>
<p> <%="SAMPLE 2 RESULT " + strBook%> </p>

</body>

Answer 1

你可以把它作为参数传递给下一个jsp。

Sample1.jsp

<form action="sample2.jsp"  method="post">
   <input type="submit" id="buttonSubmit" name="buttonSubmit" value="Buy"/>
   <input type="hidden" name="book" value="<%=strBook%>"/>
</form>

Sample2.jsp

 <% 
// Obtain strBook for rendering on current page
String strBook = (String) request.getParameter("book"); 
 %>


<h1> Book: </h1>
<p> <%="SAMPLE 2 RESULT " + strBook%> </p>