3xx Redirection

This class of status code indicates the client must take additional action to complete the request. Many of these status codes are used in URL redirection.[20]

A user agent may carry out the additional action with no user interaction only if the method used in the second request is GET or HEAD. A user agent should not automatically redirect a request more than five times[citation needed], since such redirections usually indicate an infinite loop.[21]

300 Multiple Choices
Indicates multiple options for the resource that the client may follow. It, for instance, could be used to present different format options for video, list files with different extensions, or word sense disambiguation.[22]
301 Moved Permanently
This and all future requests should be directed to the given URI.[23]
302 Found
This is an example of industry practice contradicting the standard. The HTTP/1.0 specification (RFC 1945) required the client to perform a temporary redirect (the original describing phrase was "Moved Temporarily"),[24] but popular browsers implemented 302 with the functionality of a 303 See Other. Therefore, HTTP/1.1 added status codes 303 and 307 to distinguish between the two behaviours.[25] However, some Web applications and frameworks use the 302 status code as if it were the 303.[26]
303 See Other (since HTTP/1.1)
The response to the request can be found under another URI using a GET method. When received in response to a POST (or PUT/DELETE), it should be assumed that the server has received the data and the redirect should be issued with a separate GET message.[27]
304 Not Modified (RFC 7232)
Indicates that the resource has not been modified since the version specified by the request headers If-Modified-Since or If-None-Match. This means that there is no need to retransmit the resource, since the client still has a previously-downloaded copy.[28]
305 Use Proxy (since HTTP/1.1)
The requested resource is only available through a proxy, whose address is provided in the response. Many HTTP clients (such as Mozilla[29] and Internet Explorer) do not correctly handle responses with this status code, primarily for security reasons.[30]
306 Switch Proxy
No longer used. Originally meant "Subsequent requests should use the specified proxy."[31]
307 Temporary Redirect (since HTTP/1.1)
In this case, the request should be repeated with another URI; however, future requests should still use the original URI. In contrast to how 302 was historically implemented, the request method is not allowed to be changed when reissuing the original request. For instance, a POST request should be repeated using another POST request.[32]
308 Permanent Redirect (RFC 7538)
The request, and all future requests should be repeated using another URI. 307 and 308 parallel the behaviours of 302 and 301, but do not allow the HTTP method to change. So, for example, submitting a form to a permanently redirected resource may continue smoothly.

HTTP Error 302 - Moved temporarily

Introduction

Your Web server thinks that your URL has been temporarily redirected to another URL. The client system is expected to immediately retry the alternate URL.

Fixing 302 errors - general

The 302 response from the Web server should always include an alternative URL to which redirection should occur. If it does, a Web browser will immediately retry the alternative URL. So you never actually see a 302 error in a Web browser, unless perhaps you have a corrupt redirection chain e.g. URL A redirects to URL B which in turn redirects back to URL A. If your client is not a Web browser, it should behave in the same way as a Web browser i.e. immediately retry the alternative URL.

If the Web server does not return an alternative URL with the 302 response, then either the Web server sofware itself is defective or the Webmaster has not set up the URL redirection correctly.

Fixing 302 errors - CheckUpDown

Redirection of URLs may occur for low-level URLs (specific URLs within the Web site such as www.isp.com/products/index.html) when you reorganise the web site, but is relatively uncommon for the top-level URLs (such as www.isp.com) which most CheckUpDown users ask us to check. So this error should be fairly infrequent.

The 302 response from the Web server should always include an alternative URL to which redirection should occur. If it does, CheckUpDown automatically tries the alternative URL. This in turn may possibly lead to another redirection which CheckUpDown then tries. This continues for a maximum of 5 redirections. As soon as 5 redirections have occurred, CheckUpDown gives up and reports the 302 error for your account. So you should only ever see the 302 error if 1) the Web server gives no alternative URL on the 302 response or 2) the number of redirections exceeds 5. This second condition should be fairly unlikely - and may indicate a recursive pattern e.g. URL A redirects to URL B which in turn redirects back to URL A.

You first need to check that the IP name we use to check for your account is accurate. If you or your ISP have configured something so that any access using this name should now be redirected to another name, then you need to update your CheckUpDown account to start using the new name.

If you believe that the IP name we use is exact (should not be redirected), please try accessing the current URL using a Web browser. Note carefully which URL actually gets displayed, because your browser may silently switch to a substitute URL if it receives an 302 message from the Web server. If you see any evidence of a new URL, try accessing that directly from your browser. If this works (you see the Web site as expected), then this new URL is what you may need to update on your CheckUpDown account. If this is a temporary redirection, then you may also need to reinstate the original IP name at a later date when the redirection is no longer effective.

If none of the above help, we can analyse the underlying HTTP data streams we receive from the Web server. These can provide additional information about the new URL(s) which the Web server thinks we should be accessing. Before doing this, we prefer you to identify any deliberate changes on your side, liaising with your ISP if needs be.

302 errors should occur infrequently, because top-level URLs do not change often. If they do change, then this is typically because a redirection URL is being suggested. This pervasive change is unlikely to occur by accident, so most often we can resolve this error by updating our system records for your account following a deliberate change of URL on your part, whether this change is temporary or permanent.

 

302 errors in the HTTP cycle

Any client (e.g. your Web browser or our CheckUpDown robot) goes through the following cycle when it communicates with the Web server:

  1. Obtain an IP address from the IP name of the site (the site URL without the leading 'http://'). This lookup (conversion of IP name to IP address) is provided by domain name servers (DNSs).
  2. Open an IP socket connection to that IP address.
  3. Write an HTTP data stream through that socket.
  4. Receive an HTTP data stream back from the Web server in response. This data stream contains status codes whose values are determined by the HTTP protocol. Parse this data stream for status codes and other useful information.

This error occurs in the final step above when the client receives an HTTP status code that it recognises as '302'.

10.3 Redirection 3xx

This class of status code indicates that further action needs to be taken by the user agent in order to fulfill the request. The action required MAY be carried out by the user agent without interaction with the user if and only if the method used in the second request is GET or HEAD. A client SHOULD detect infinite redirection loops, since such loops generate network traffic for each redirection.

      Note: previous versions of this specification recommended a
      maximum of five redirections. Content developers should be aware
      that there might be clients that implement such a fixed
      limitation.

10.3.1 300 Multiple Choices

The requested resource corresponds to any one of a set of representations, each with its own specific location, and agent- driven negotiation information (section 12) is being provided so that the user (or user agent) can select a preferred representation and redirect its request to that location.

Unless it was a HEAD request, the response SHOULD include an entity containing a list of resource characteristics and location(s) from which the user or user agent can choose the one most appropriate. The entity format is specified by the media type given in the Content- Type header field. Depending upon the format and the capabilities of

the user agent, selection of the most appropriate choice MAY be performed automatically. However, this specification does not define any standard for such automatic selection.

If the server has a preferred choice of representation, it SHOULD include the specific URI for that representation in the Location field; user agents MAY use the Location field value for automatic redirection. This response is cacheable unless indicated otherwise.

10.3.2 301 Moved Permanently

The requested resource has been assigned a new permanent URI and any future references to this resource SHOULD use one of the returned URIs. Clients with link editing capabilities ought to automatically re-link references to the Request-URI to one or more of the new references returned by the server, where possible. This response is cacheable unless indicated otherwise.

The new permanent URI SHOULD be given by the Location field in the response. Unless the request method was HEAD, the entity of the response SHOULD contain a short hypertext note with a hyperlink to the new URI(s).

If the 301 status code is received in response to a request other than GET or HEAD, the user agent MUST NOT automatically redirect the request unless it can be confirmed by the user, since this might change the conditions under which the request was issued.

      Note: When automatically redirecting a POST request after
      receiving a 301 status code, some existing HTTP/1.0 user agents
      will erroneously change it into a GET request.

10.3.3 302 Found

The requested resource resides temporarily under a different URI. Since the redirection might be altered on occasion, the client SHOULD continue to use the Request-URI for future requests. This response is only cacheable if indicated by a Cache-Control or Expires header field.

The temporary URI SHOULD be given by the Location field in the response. Unless the request method was HEAD, the entity of the response SHOULD contain a short hypertext note with a hyperlink to the new URI(s).

If the 302 status code is received in response to a request other than GET or HEAD, the user agent MUST NOT automatically redirect the request unless it can be confirmed by the user, since this might change the conditions under which the request was issued.

      Note: RFC 1945 and RFC 2068 specify that the client is not allowed
      to change the method on the redirected request.  However, most
      existing user agent implementations treat 302 as if it were a 303
      response, performing a GET on the Location field-value regardless
      of the original request method. The status codes 303 and 307 have
      been added for servers that wish to make unambiguously clear which
      kind of reaction is expected of the client.

10.3.4 303 See Other

The response to the request can be found under a different URI and SHOULD be retrieved using a GET method on that resource. This method exists primarily to allow the output of a POST-activated script to redirect the user agent to a selected resource. The new URI is not a substitute reference for the originally requested resource. The 303 response MUST NOT be cached, but the response to the second (redirected) request might be cacheable.

The different URI SHOULD be given by the Location field in the response. Unless the request method was HEAD, the entity of the response SHOULD contain a short hypertext note with a hyperlink to the new URI(s).

      Note: Many pre-HTTP/1.1 user agents do not understand the 303
      status. When interoperability with such clients is a concern, the
      302 status code may be used instead, since most user agents react
      to a 302 response as described here for 303.

10.3.5 304 Not Modified

If the client has performed a conditional GET request and access is allowed, but the document has not been modified, the server SHOULD respond with this status code. The 304 response MUST NOT contain a message-body, and thus is always terminated by the first empty line after the header fields.

The response MUST include the following header fields:

      - Date, unless its omission is required by section 14.18.1

If a clockless origin server obeys these rules, and proxies and clients add their own Date to any response received without one (as already specified by [RFC 2068], section 14.19), caches will operate correctly.

      - ETag and/or Content-Location, if the header would have been sent
        in a 200 response to the same request
      - Expires, Cache-Control, and/or Vary, if the field-value might
        differ from that sent in any previous response for the same
        variant

If the conditional GET used a strong cache validator (see section 13.3.3), the response SHOULD NOT include other entity-headers. Otherwise (i.e., the conditional GET used a weak validator), the response MUST NOT include other entity-headers; this prevents inconsistencies between cached entity-bodies and updated headers.

If a 304 response indicates an entity not currently cached, then the cache MUST disregard the response and repeat the request without the conditional.

If a cache uses a received 304 response to update a cache entry, the cache MUST update the entry to reflect any new field values given in the response.

10.3.6 305 Use Proxy

The requested resource MUST be accessed through the proxy given by the Location field. The Location field gives the URI of the proxy. The recipient is expected to repeat this single request via the proxy. 305 responses MUST only be generated by origin servers.

      Note: RFC 2068 was not clear that 305 was intended to redirect a
      single request, and to be generated by origin servers only.  Not
      observing these limitations has significant security consequences.

10.3.7 306 (Unused)

The 306 status code was used in a previous version of the specification, is no longer used, and the code is reserved.

10.3.8 307 Temporary Redirect

The requested resource resides temporarily under a different URI. Since the redirection MAY be altered on occasion, the client SHOULD continue to use the Request-URI for future requests. This response is only cacheable if indicated by a Cache-Control or Expires header field.

The temporary URI SHOULD be given by the Location field in the response. Unless the request method was HEAD, the entity of the response SHOULD contain a short hypertext note with a hyperlink to the new URI(s) , since many pre-HTTP/1.1 user agents do not understand the 307 status. Therefore, the note SHOULD contain the information necessary for a user to repeat the original request on the new URI.

If the 307 status code is received in response to a request other than GET or HEAD, the user agent MUST NOT automatically redirect the request unless it can be confirmed by the user, since this might change the conditions under which the request was issued.

3xx Redirection的更多相关文章

  1. HTTP状态码(2xx,3xx,4xx,5xx)

    HTTP状态码负责表示客户端请求的返回结果,标记服务器的处理结果. HTTP常用状态码分为5种:   类别 原因短语 1xx Informational(信息状态码) 接受请求正在处理 2xx Suc ...

  2. 前端学HTTP之报文首部

    前面的话 首部和方法配合工作,共同决定了客户端和服务器能做什么事情.在请求和响应报文中都可以用首部来提供信息,有些首部是某种报文专用的,有些首部则更通用一些.本文将详细介绍HTTP报文中的首部 结构 ...

  3. 前端学HTTP之报文起始行

    前面的话 如果说HTTP是因特网的信使,那么HTTP报文就是它用来搬东西的包裹了.HTTP报文是在HTTP应用程序之间发送的简单的格式化数据块,每条报文都包含一条来自客户端的请求,或者一条来自服务器的 ...

  4. 常用的14种HTTP状态码速查手册

    分类 1xx \> Information(信息) // 接收的请求正在处理 2xx \> Success(成功) // 请求正常处理完毕 3xx \> Redirection(重定 ...

  5. HTTP状态码

    http状态码负责表示客户端HTTP请求的返回结果.标记服务器端的处理是否正常.通知出现的错误等工作. 状态码类别分组如下: 1. 1XX: informational(信息性状态码)  接收的请求正 ...

  6. 「理解HTTP」之常见的状态码segmentfault

    状态码的职责是当客户端向服务器端发送请求时,描述返回请求结果.借助状态码,用户可以知道服务器端是正常处理了请求,还是出现了什么错误. RFC2616定义的状态码,由3位数字和原因短信组成.数字中的第一 ...

  7. 16-1-27---图解HTTP(02)

    图解HTTP第四章 返回结果的HTTP状态码    HTTP状态码负责表示客户端HTTP请求的返回结果.标记服务器端的处理是否正常.通知出现错误等工作.4.1状态码告知从服务器端返回的请求结果     ...

  8. http-code 未译

    1xx Informational Request received, continuing process. This class of status code indicates a provis ...

  9. Http基础

    Http基础 这篇文章是讲Android网络请求的先导文章,主要讲Http工作流程,请求报文和响应报文的格式,以及GET和POST方法的具体含义. Http工作流程 HTTP是一个客户端和服务器端请求 ...

随机推荐

  1. 《高质量程序设计指南:C++/C语言》面试题整理

    本试题仅用于考查C++/C程序员的基本编程技能.内容限于C++/C常用 语法,不涉及 数据结构. 算法以及深奥的语法.考试成绩能反映出考生的编程质量以及对C++/C的理解程度,但不能反映考生的智力和软 ...

  2. c++,为什么要引入虚拟继承

      虚拟基类是为解决多重继承而出现的.   以下面的一个例子为例: #include <iostream.h> #include <memory.h> class CA { i ...

  3. Java基础08 继承

    作者:Vamei 出处:http://www.cnblogs.com/vamei 欢迎转载,也请保留这段声明.谢谢! 继承(inheritance)是面向对象的重要概念.继承是除组合(composit ...

  4. const对象默认是static的,而不是extern的

    const 和 static 变量,可以放在头文件中 const对象默认是static的,而不是extern的,所以即使放在头文件中声明和定义.多个cpp引用同一个头文件,互相也没有感知,所以不会导致 ...

  5. PHP $_SERVER

    $_SERVER 是一个包括了诸如头信息(header).路径(path).以及脚本位置(script locations)等等信息的数组.这个数组中的项目由 Web server创建.不能保证每一个 ...

  6. 【视频】零基础学Android开发:蓝牙聊天室APP(四)

    零基础学Android开发:蓝牙聊天室APP第四讲 4.1 ListView控件的使用 4.2 BaseAdapter具体解释 4.3 ListView分布与滚动事件 4.4 ListView事件监听 ...

  7. Winfrom 文本框回车进入下一个个单元格(TextBox)

    1.重写方法 OnShown protected override void OnShown(EventArgs e) { base.OnShown(e); foreach (Control ct i ...

  8. mfc修改应用程序外观

    1.在窗口创建前修改窗体外观 在BOOL CMainFrame::PreCreateWindow(CREATESTRUCT& cs)函数中修改,其中CREATESTRUCT结构中有诸如窗口大小 ...

  9. 树莓派的.bashrc和.bash_aliases文件

    在你的home文件夹中,你能够找到一个包括用户配置的隐藏文件.bashrc. 你能够依据自己的须要改动这个文件. 文件里为你提供了一些实用的调整设置.默认情况下当中一些设置是被凝视掉的. 比如,一些l ...

  10. JQuery Ajax实例总结

    jQuery确实是一个挺好的轻量级的JS框架,能帮助我们快速的开发JS应用,并在一定程度上改变了我们写JavaScript代码的习惯. 废话少说,直接进入正题,我们先来看一些简单的方法,这些方法都是对 ...