一、应用背景

JSP取得Servlet中放入request的List，将List中的数据拼装成XML。以下代码在Eclipse的内置浏览器中显示为xml，没有问题。

[java] 
/**
 * 新闻Servlet
 * @author 徐越
 *
 */ 
public class ListServlet extends HttpServlet 
{ 
 private static final long serialVersionUID = 1L; 
 private VideoNewsService vs = new VideoNewsServiceImpl(); 
 
 protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException 
 { 
  doPost(request, response); 
 } 
 
 protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException 
 { 
  List<VideoNews> news = vs.readNews(); 
  request.setAttribute("lstnews", news); 
  request.getRequestDispatcher("/WEB-INF/pages/news.jsp").forward(request, response); 
 } 
} 

/**
 * 新闻Servlet
 * @author 徐越
 *
 */
public class ListServlet extends HttpServlet
{
 private static final long serialVersionUID = 1L;
 private VideoNewsService vs = new VideoNewsServiceImpl();

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

 protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
 {
  List<VideoNews> news = vs.readNews();
  request.setAttribute("lstnews", news);
  request.getRequestDispatcher("/WEB-INF/pages/news.jsp").forward(request, response);
 }
}
[html]
<%@ page language="java" contentType="text/xml; charset=utf-8" pageEncoding="utf-8"%> 
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %> 
<?xml version="1.0" encoding="UTF-8"?> 
<videoNews> 
 <c:forEach items="${lstnews}" var="n"> 
  <news id="${n.id }"> 
   <title>${n.title }</title> 
   <length>${n.timeLength }</length> 
  </news> 
 </c:forEach> 
</videoNews> 

<%@ page language="java" contentType="text/xml; charset=utf-8" pageEncoding="utf-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<?xml version="1.0" encoding="UTF-8"?>
<videoNews>
 <c:forEach items="${lstnews}" var="n">
  <news id="${n.id }">
   <title>${n.title }</title>
   <length>${n.timeLength }</length>
  </news>
 </c:forEach>
</videoNews>

二、发现问题

火狐中报错：XML解析错误：XML 或文本声明不在实体的开头

chrome报错：XML declaration allowed only at the start of the document

根据错误信息，可以知道XML声明<?xml version="1.0" encoding="UTF-8"?>必须在文档的开头。

三、解决问题

将page、taglib、xml同时放在第一行即可，一个接一个的后面。虽然不好看，但是解决问题哦