Servlets，JPA，JSP - Servlet无法正常工作

我不知道为什么我的servlet无法正常工作。我的代码波纹管：Servlets，JPA，JSP - Servlet无法正常工作

userOrdersServlet.java

@WebServlet("/userOrders") 
public class userOrdersServlet extends HttpServlet { 
    private static final long serialVersionUID = 1L; 
protected void doPost(HttpServletRequest request, HttpServletResponse response) 
      throws ServletException, IOException { 
     HttpSession session = request.getSession(); 
     int userId = (int) session.getAttribute("userId"); 
     UserDAO daoUser = (UserDAO) request.getAttribute("userDao"); 
     User user = daoUser.getUser(userId); 
     List<Books> booksOrderedByUser = user.getBooks(); 
     request.setAttribute("booksOrderedByUser", booksOrderedByUser); 
     request.getRequestDispatcher("/userOrders.jsp").forward(request, response); 

    } 

}

userDAO.java

public User getUser(int id) { 
     this.em.clear(); 
     return this.em.find(User.class, id); 
    }

userOrders.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1" 
pageEncoding="ISO-8859-1"%> 
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%> 
<!DOCTYPE html> 
<html> 
<head> 
<link href="style.css" rel="stylesheet" type="text/css" /> 
<title>Library Online</title> 
</head> 
<body> 
<div id="container"> 
    <%@include file="templateTop.jsp" %> 
<div class="main"><table border="1"> 
    <h2>Your orders</h2> 
      <tr> 
       <td>Title</td> 
       <td>Author</td> 
       <td>Description</td> 
       <td>Category</td> 
       <td>Year</td> 
      </tr> 
      <c:forEach var="booksOrdered" items="${booksOrderedByUser}"> 
       <tr> 
        <td>${booksOrdered.title}</td> 
        <td>${booksOrdered.author}</td> 
        <td>${booksOrdered.description}</td> 
        <td>${booksOrdered.category}</td> 
        <td>${booksOrdered.year}</td> 
        </tr> 
      </c:forEach> 
      </table> 
    </div> 
        </div> 
      <div style="clear:both"></div> 

    <br> 


</body> 
</html>

的web.xml

<?xml version="1.0" encoding="UTF-8"?> 
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0"> 
<display-name>RegisterLoginJPA</display-name> 
<welcome-file-list> 
<welcome-file>/index.jsp</welcome-file> 
</welcome-file-list> 
<filter> 
<filter-name>sessionFilter</filter-name> 
<filter-class>filters.sessionFilter</filter-class> 
</filter> 
<filter-mapping> 
<filter-name>sessionFilter</filter-name> 
<url-pattern>/loginSuccess.jsp</url-pattern> 
<dispatcher>REQUEST</dispatcher> 
</filter-mapping> 
</web-app>

因此，我使用userOrdersServlet.java中的代码，并使用foreach循环显示数据，并在另一个servlet中显示System.out.println()，它工作正常。但是当我去userOrders.jsp它不显示任何数据，我做错了什么？

来源

2015-12-07 Valery

安置自己的web.xml和你userOrder.jsp的休息吧。你还面临什么错误？ – Perdomoff

我没有注意到任何错误，每个其他的servlet运行良好，我把简单的重定向到doGet方法在这个servlet中，仍然无法正常工作。 – Valery

你想完成什么？你的预期产出是多少？ – Perdomoff

要访问JSP中的请求参数，您需要在参数名称前加上“param”。所以

<c:forEach var="booksOrdered" items="${booksOrderedByUser}">

应该是：

<c:forEach var="booksOrdered" items="${param.booksOrderedByUser}">

见：JSP Expression Language get parameter

来源

2015-12-07 20:59:12 mmulholl

Servlets，JPA，JSP - Servlet无法正常工作

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