Redirect or Forward

本文探讨了在Java Web应用中使用过滤器(Filter)时遇到的问题,特别是在设置错误信息并试图通过重定向显示这些信息时发生的异常。文章详细解释了如何正确地使用请求转发(request forwarding)来避免这些问题,并确保能在错误页面正确显示错误信息。

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如果页面/bb/a.jsp
假设我们有一个Filter的配置为:/bb/*,其中有一段代码为
if( need condition)
   request.setAttribute("errormessage","The Error info.");
   response.sendRedirect(ERROR_FOR_SOME_)
/if
在出错的页面不会看到预期的错误提示,
error_page.jsp
  <c:out value="${errormessage}"></c:out>
Of course we cannot see any error info here,because of using the "sendRedirect"!!!
注意:redirect!!!修改为:
  request.getRequestDispatcher(ERROR_FOR_SOME_).forward(request,response);
问题可解决
如果又在/bb/a.jsp页面中使用了:
<jsp:forward page="/some.jsp"/>
Error:Cannot forward after response has been committed
ping 114.114.114.114 PING 114.114.114.114 (114.114.114.114) 56(84) bytes of data. From 10.101.10.57 icmp_seq=1 Redirect Network(New nexthop: 10.101.255.254) From 10.101.10.57: icmp_seq=1 Redirect Network(New nexthop: 10.101.255.254) From 10.101.10.57 icmp_seq=1 Redirect Network(New nexthop: 10.101.255.254) From 10.101.10.57: icmp_seq=1 Redirect Network(New nexthop: 10.101.255.254) From 10.101.10.57 icmp_seq=2 Redirect Network(New nexthop: 10.101.255.254) From 10.101.10.57: icmp_seq=2 Redirect Network(New nexthop: 10.101.255.254) From 10.101.10.57 icmp_seq=2 Redirect Network(New nexthop: 10.101.255.254) From 10.101.10.57: icmp_seq=2 Redirect Network(New nexthop: 10.101.255.254) From 10.101.10.57 icmp_seq=3 Redirect Network(New nexthop: 10.101.255.254) From 10.101.10.57: icmp_seq=3 Redirect Network(New nexthop: 10.101.255.254) From 10.101.10.57 icmp_seq=3 Redirect Network(New nexthop: 10.101.255.254) From 10.101.10.57: icmp_seq=3 Redirect Network(New nexthop: 10.101.255.254) ^C --- 114.114.114.114 ping statistics --- 3 packets transmitted, 0 received, +6 errors, 100% packet loss, time 2003ms [magician@localhost ~]$ sudo systemctl stop firewalld [sudo] magician 的密码: [magician@localhost ~]$ iptables -L -n modprobe: ERROR: could not insert 'ip_tables': Operation not permitted iptables v1.4.21: can't initialize iptables table `filter': Table does not exist (do you need to insmod?) Perhaps iptables or your kernel needs to be upgraded. [magician@localhost ~]$ sudo iptables -L -n Chain INPUT (policy ACCEPT) target prot opt source destination Chain FORWARD (policy ACCEPT) target prot opt source destination Chain OUTPUT (policy ACCEPT) target prot opt source destination [magician@localhost ~]$ cat /etc/resolv.conf # Generated by NetworkManager nameserver 114.114.114.114 [magician@localhost ~]$
03-11
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