我在我的jsp中使用jstl，并且我的jsp的所有元素都在显示，除了JSTL forEach标记之外，放在此循环中的所有内容都将消失。
这是我的jsp：
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%@ taglib prefix="fn" uri="http://java.sun.com/jsp/jstl/functions" %>
<!DOCTYPE html>
<html lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<meta charset="UTF-8">
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>Details</title>
<base href="${pageContext.request.contextPath}/">
<link href="https://fonts.googleapis.com/css?family=Arvo" rel="stylesheet">
<meta name="description"
content="A free shopping cart system. OpenCart is an open source">
<link href="Resources/bootstrap.css" rel="stylesheet">
<link href="Resources/stylesheet.css" rel="stylesheet">
<link href="Resources/font-awesome.min.css" rel="stylesheet">
<link href="Resources/bootstrap-datetimepicker.min.css" type="text/css" rel="stylesheet" media="screen">
<script type="text/javascript" async="" src="Resources/analytics.js.download"></script>
<script src="Resources/jquery-1.12.2.min.js.download"></script>
<script src="Resources/bootstrap.min.js.download"></script>
<script src="Resources/moment.js.download" type="text/javascript"></script>
<script src="Resources/bootstrap-datetimepicker.min.js.download" type="text/javascript"></script>
<script src="Resources/common.js.download"></script>
<script async="" src="Resources/js"></script>
<script>
window.dataLayer = window.dataLayer || [];
function gtag() {
dataLayer.push(arguments);
}
gtag('js', new Date());
gtag('config', 'UA-1988725-1');
</script>
</head>
<body>
<header>
<jsp:include page="header.jsp"/>
</header>
<div id="common-home">
<div id="hero">
<div class="container" style="height: 150px;">
<div class="row">
<jsp:include page="searchbar.html"/>
</div>
<div class="hidden-md hidden-lg"><img src="Resources/hero-image.png"
alt="The best FREE and open-source eCommerce platform"
title="The best FREE and open-source eCommerce platform"
class="img-responsive"></div>
</div>
<div class="device hidden-xs hidden-sm"><img src="Resources/hero-image.png"
alt="The best FREE and open-source eCommerce platform"
title="The best FREE and open-source eCommerce platform"
class="hidden"></div>
</div>
<div id="support" class="container text-center" style="padding-top: 30px">
<div class="row">
<div class="col-sm-6" style="margin-left:300px">
<c:forEach items="${best}" var="item" >
<div style="text-align: center"><h2 style="display: inline-block; white-space: nowrap">${item.name}</h2></div>
<img src="Resources/images/${item.imageUrl}" alt="Dedicated Support"
title="Dedicated Support">
<p style="margin-bottom: 0px">Author: ${item.author}</p>
<p>Price : ${item.price}</p>
</c:forEach>
<p>
<a href="https://dedicated.opencart.com/" target="_blank" class="btn btn-primary btn-lg hidden-xs">Add To Cart</a>
<a href="https://dedicated.opencart.com/" target="_blank"
class="btn btn-primary btn-lg btn-block visible-xs">Add To Cart</a>
</p>
</div>
</div>
</div>
</div>
<jsp:include page="footer.html"/>
<script type="text/javascript"><!--
if (typeof (Zenbox) !== "undefined") {
Zenbox.init({
dropboxID: "20269606",
url: "https://opencart.zendesk.com",
tabTooltip: "Support",
tabImageURL: "https://assets.zendesk.com/external/zenbox/images/tab_support.png",
tabColor: "black",
tabPosition: "Left"
});
}
//--></script>
</body>
</html>
这是我的Servlet文件：
package servlets;
import entities.CategoryClass;
import entities.ItemClass;
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import javax.persistence.Query;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.List;
@WebServlet(name = "CategoryServlet",urlPatterns = "/foo/*")
public class CategoryServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
EntityManagerFactory entityManagerFactory = Persistence.createEntityManagerFactory("NewPersistenceUnit");
EntityManager entityManager = entityManagerFactory.createEntityManager();
Query query = entityManager.createQuery("SELECT c FROM CategoryClass c");
List<CategoryClass> categories = query.getResultList();
request.setAttribute("categories",categories);
String url = "/shopindex.jsp" ;
String action = request.getParameter("action");
if(action != null){
// age action null nis ,
if (action.equals("search")){
String keyword = request.getParameter("searchedword");
Query query1 = entityManager.createQuery("from ItemClass where name like '%" + keyword + " %'" );
List<ItemClass> items = query1.getResultList();
request.setAttribute("items",items);
url = "/search.jsp" ;
}
if (action.equals("itemDetails")){
String productId = request.getParameter("id");
Query query2 = entityManager.createQuery("from ItemClass where id="+productId);
List<ItemClass> itemThatWeWantedTheirDetails = query2.getResultList();
request.setAttribute("itemThatWeWantedTheirDetails",itemThatWeWantedTheirDetails);
url = "/itemDetails.jsp";
}
if (action.equals("best")){
Query query3 = entityManager.createQuery("select i.name from ItemClass i where i.bought = (select max(ii.bought) from ItemClass ii )");
List<ItemClass> best = query3.getResultList();
request.setAttribute("best",best);
int size = best.size();
request.setAttribute("size1",size);
url = "/besty.jsp";
}
}
request.getServletContext().getRequestDispatcher(url).forward(request,response);
entityManager.close();
entityManagerFactory.close();
}
}
我在另一个jsp中具有完全相同的条件，并且可以正常工作，但是我不明白为什么会有问题。
感谢您的帮助。
答案 0 :(得分：1)
您需要检查您的网址是否包含查询字符串yoururl?action=best
需要检查List<ItemClass> best = query3.getResultList();中的最佳值是否为空或为空
如果满足两个条件，则必须显示最佳状态。