Java Servlet 将数组列表作为请求属性发送到 JSP
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Servlet send arraylist to JSP as request attribute
提问by Nathaniel Wendt
I am attempting to send an ArrayList from a servlet to a JSP page. In the Servlet:
我正在尝试将 ArrayList 从 servlet 发送到 JSP 页面。在 Servlet 中：
List<ItemObj> myList = new ArrayList<ItemObj>();
req.setAttribute("list", myList);
req.getRequestDispatcher("page.jsp").forward(req,resp);
In the JSP:
在 JSP 中：
<% List<ItemObj> myList = (ArrayList<ItemObj>) request.getParameter("list"); %>
However, I keep getting an error: Cannot cast from String to List. I have found sources that indicate that I can cast as such:
但是，我不断收到错误消息：无法从字符串转换为列表。我找到了表明我可以这样投射的来源：
how to send ArrayList from jsp to servlet
Send array of objects from servlet to JSP
What am I doing wrong? Thank you!
我究竟做错了什么？谢谢！
采纳答案by Keerthivasan
You are setting listas request attribute and getting it back as request parameter
您正在设置list为请求属性并将其作为请求参数取回
Use <% List<ItemObj> myList = (ArrayList<ItemObj>) request.getAttribute("list"); %>
用 <% List<ItemObj> myList = (ArrayList<ItemObj>) request.getAttribute("list"); %>
回答by Santino 'Sonny' Corleone
Instead of request.getParameteruse
而不是request.getParameter使用
<% List<ItemObj> myList = (ArrayList<ItemObj>) request.getAttribute("list"); %>
<% List<ItemObj> myList = (ArrayList<ItemObj>) request.getAttribute("list"); %>
request.getParameteris used to retrieve form parameters.
request.getParameter用于检索表单参数。
回答by Kode Charlie
Sotirious is spot-on. You need to call getAttribute.
Sotiirious 恰到好处。您需要调用 getAttribute。
But beyond that, you should be privy to the scope of your attribute: is it scoped to (i) page, (ii) request, (iii) session, or (iv) application?
但除此之外，您应该了解属性的范围：它的范围是 (i) 页面、(ii) 请求、(iii) 会话还是 (iv) 应用程序？
I don't know the default scope off-hand, but you might want to look into that.
我不知道现成的默认范围，但您可能想研究一下。
回答by Sagar Sane
You need request.getAttribute()instead of request.getParameter()
你需要request.getAttribute()而不是request.getParameter()
