链接过来的时候，referer的值是链接过来的页面的URL，正常。我刷新的时候referer的值没有变，但当我在地址栏中打回车（URL没有改变，只是打回车），referer值却变成NULL了。

1）：链接过来和在地址栏中直接输入URL，有没有什么区别？如果有，有什么区别？
2）：刷新的时候URL为什么不变，为什么还是前一个URL地址，为什么不变成当前的URL？
3）：直接输入为什么得不到 <%=request.getHeader("REFERER")的值？

如果是直接在浏览器里输入有referer的页面，返回是null，也就是说referer只有从别的页面点击连接来到这页的才会有内容。为NULL就是手工，非null就是连接过来的。刷新的时候，会检查服务端是否会有更新，没有的话，则使用本机的缓存，也就是说，你刷新时得到的响应依然是

<%@ page import="java.util.*" %>

  
     
     
  
  
     

HTTP Request Headers Received

     
      <%
         Enumeration eNames = request.getHeaderNames();
         while (eNames.hasMoreElements()) {
            String name = (String) eNames.nextElement();
            String value = normalize(request.getHeader(name));
      %>
        
      <%
         }
      %>
     

<%= name %>

<%= value %>

  

<%!
   private String normalize(String value)
   {
      StringBuffer sb = new StringBuffer();
      for (int i = 0; i < value.length(); i++) {
         char c = value.charAt(i);
         sb.append(c);
         if (c == ';')
            sb.append("
");
      }
      return sb.toString();
   }
%>

综合实例

index.jsp
 

   
       
   
 
   
       

Getting Header Data

       

           
       

   

 
basic.jsp
 

   
       
   

   
       

Reading Header Information

        Here are the request headers and their data:
       

        <% java.util.Enumeration names = request.getHeaderNames();
        while(names.hasMoreElements()){
            String name = (String) names.nextElement();
            out.println(name + ":
" + request.getHeader(name) + "

");
        }
        %>
   

通过方法可以知道访问者的request.getHeader("Referer");其他的方法下列
System.out.println("Protocol: " + request.getProtocol());
System.out.println("Scheme: " + request.getScheme());
System.out.println("Server Name: " + request.getServerName() );
System.out.println("Server Port: " + request.getServerPort());
System.out.println("Protocol: " + request.getProtocol());
System.out.println("Server Info: " + getServletConfig().getServletContext().getServerInfo());
System.out.println("Remote Addr: " + request.getRemoteAddr());
System.out.println("Remote Host: " + request.getRemoteHost());
System.out.println("Character Encoding: " + request.getCharacterEncoding());
System.out.println("Content Length: " + request.getContentLength());
System.out.println("Content Type: "+ request.getContentType());
System.out.println("Auth Type: " + request.getAuthType());
System.out.println("HTTP Method: " + request.getMethod());
System.out.println("Path Info: " + request.getPathInfo());
System.out.println("Path Trans: " + request.getPathTranslated());
System.out.println("Query String: " + request.getQueryString());
System.out.println("Remote User: " + request.getRemoteUser());
System.out.println("Session Id: " + request.getRequestedSessionId());
System.out.println("Request URI: " + request.getRequestURI());
System.out.println("Servlet Path: " + request.getServletPath());
System.out.println("Accept: " + request.getHeader("Accept"));
System.out.println("Host: " + request.getHeader("Host"));
System.out.println("Referer : " + request.getHeader("Referer"));
System.out.println("Accept-Language : " + request.getHeader("Accept-Language"));
System.out.println("Accept-Encoding : " + request.getHeader("Accept-Encoding"));
System.out.println("User-Agent : " + request.getHeader("User-Agent"));
System.out.println("Connection : " + request.getHeader("Connection"));
System.out.println("Cookie : " + request.getHeader("Cookie"));
System.out.println("Created : " + session.getCreationTime());
System.out.println("LastAccessed : " + session.getLastAccessedTime());