Java 即使发送了属性，JSP代码也显示null
我没有主意了。我打印了我从Servlet发送的ArrayList书籍，它一直显示null。当我在Servlet中打印该数组时，它显示了正确的数据集。也许你能帮我： 这是Servlet：Java 即使发送了属性，JSP代码也显示null,java,jsp,servlets,requestdispatcher,Java,Jsp,Servlets,Requestdispatcher,我没有主意了。我打印了我从Servlet发送的ArrayList书籍，它一直显示null。当我在Servlet中打印该数组时，它显示了正确的数据集。也许你能帮我： 这是Servlet： private void listBookedPlaces(HttpServletRequest request, HttpServletResponse response) throws Exception { // get list of booked places from db
private void listBookedPlaces(HttpServletRequest request, HttpServletResponse response)
throws Exception {
// get list of booked places from db util
List<Book> books = bookDbUtil.getBooks();
// add booked places to the request
request.setAttribute("BOOKED_LIST", books); // set Attribute (-name "BOOKED_LIST", -value books);
// send to JSP page (view)
RequestDispatcher dispatcher = request.getRequestDispatcher("/list-book.jsp");
dispatcher.forward(request, response);
}
private void listBookedPlaces（HttpServletRequest请求，HttpServletResponse响应）
抛出异常{
//从db util获取预订位置列表
List books=bookDbUtil.getBooks（）；
//将预订的座位添加到请求中
request.setAttribute（“BOOKED_LIST”，books）；//set属性（-name“BOOKED_LIST”，value books）；
//发送到JSP页面（视图）
RequestDispatcher=request.getRequestDispatcher（“/list book.jsp”）；
转发（请求、响应）；
}
<%@ page contentType="text/html" pageEncoding="UTF-8"%>
<%@ page import="java.util.*, com.pbs.web.jdbc.*" %>
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>PSBS - Booked Parking Spaces Tracker</title>
</head>
<%
// "BOOKED-LIST" is attribiute name set in ControllerServlet
List<Book> theBooks =
(List<Book>) request.getAttribute("BOOKED_LIST");
%>
<body>
<%= theBooks %>
</body>
</html>
PSBS-预订停车位跟踪系统
有什么想法吗？根据此代码
List<Book> theBooks = (List<Book>) request.getAttribute("BOOKED_LIST");
List thebook=（List）request.getAttribute（“BOOKED_List”）；
<%
for (int i = 0; i < theBooks.size(); i++)
{
System.out.println(theBooks.get(i).toString());
}
%>
根据此代码
List<Book> theBooks = (List<Book>) request.getAttribute("BOOKED_LIST");
List thebook=（List）request.getAttribute（“BOOKED_List”）；
<%
for (int i = 0; i < theBooks.size(); i++)
{
System.out.println(theBooks.get(i).toString());
}
%>
您的项目是否使用mvc概念构建？如果是这样，那么我假设您有一个bean book类，也许这是其中之一：
public int getBookID() {
return bookID;
}
<%@ page contentType="text/html" pageEncoding="UTF-8"%>
<%@ page import="java.util.*, com.pbs.web.jdbc.*" %>
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>PSBS - Booked Parking Spaces Tracker</title>
</head>
<%
// "BOOKED-LIST" is attribiute name set in ControllerServlet
%>
<body>
<c:forEach var="bookBean" items="${BOOKED_LIST}">
<tr>
<td>${bookBean.getBookID()}</td>
</tr>
</c:forEach>
</body>
</html>
PSBS-预订停车位跟踪系统
${bookBean.getBookID（）}
public int getBookID() {
return bookID;
}
<%@ page contentType="text/html" pageEncoding="UTF-8"%>
<%@ page import="java.util.*, com.pbs.web.jdbc.*" %>
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>PSBS - Booked Parking Spaces Tracker</title>
</head>
<%
// "BOOKED-LIST" is attribiute name set in ControllerServlet
%>
<body>
<c:forEach var="bookBean" items="${BOOKED_LIST}">
<tr>
<td>${bookBean.getBookID()}</td>
</tr>
</c:forEach>
</body>
</html>
PSBS-预订停车位跟踪系统
${bookBean.getBookID（）}