重定向Http status code 303 和 302

╰半夏微凉° 2022-07-16 07:44 204阅读 0赞

1.  http 302
2.  http 303

# Http 302 #

302是一个普通的重定向代码。直观的看来是，请求者（浏览器或者模拟http请求）发起一个请求，然后服务端重定向到另一个地址。而事实上，服务端仅仅是增加一条属性到header，location=重定向地址。而一般的，浏览器会自动的再去请求这个location，重新获取资源。也就是说，这个会使得浏览器发起两次请求。

**Example**

Client request:

> GET /index.html HTTP/1.1  
> Host: www.example.com

Server response:

> HTTP/1.1 302 Found  
> Location: [http://www.iana.org/domains/example/][http_www.iana.org_domains_example]

## 实验 ##

1.  首先，我们用一个Map来存储信息，key为username，value为随机数。
2.  当我请求list的时候，跳转到users，来获取所有的用户。

Map<String, Double> users = new HashMap<>(); @RequestMapping(value = "/list", method = RequestMethod.GET) public String index(){ return "redirect:/users"; } @ResponseBody @RequestMapping(value = "/users", method = RequestMethod.GET) public ResponseEntity getUsers(){ ResponseEntity responseEntity = new ResponseEntity(users, HttpStatus.OK); return responseEntity; }

当时用浏览器访问的时候，会明显的看到浏览器地址变了，也就是说我明明请求的是list，结果你给我变成了users。然而，由于浏览器帮我们做了跳转的工作，我们感觉不出来，但从地址栏还是可以看到的。

**查看**  
通过拦截请求可以看出来，访问了两次：  
![686418-20160908223534363-1357573526.png][]

并且list是302，而users是200.也就是说list进行了重定向。再来看list的response：

Request URL:https://localhost:8443/list
    Request Method:GET
    Status Code:302 
    Remote Address:127.0.0.1:8888
    
    Response Headers
    view source
    Cache-Control:no-cache, no-store, max-age=0, must-revalidate
    Content-Language:zh-CN
    Content-Length:0
    Date:Thu, 08 Sep 2016 14:31:33 GMT
    Expires:0
    Location:https://localhost:8443/users
    Pragma:no-cache
    Strict-Transport-Security:max-age=31536000 ; includeSubDomains
    X-Application-Context:application:dev:8443
    X-Content-Type-Options:nosniff
    X-Frame-Options:DENY
    X-XSS-Protection:1; mode=block
    
    Request Headers
    view source
    Accept:text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
    Accept-Encoding:gzip, deflate, sdch, br
    Accept-Language:zh-CN,zh;q=0.8
    Authorization:Basic YWRtaW46dGVzdA==
    Connection:keep-alive
    Host:localhost:8443
    Upgrade-Insecure-Requests:1
    User-Agent:Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/52.0.2743.82 Safari/537.36

最关键的就是location：

> Location:[https://localhost:8443/users][https_localhost_8443_users]  
> 浏览器获取到这个资源定位后就GET访问获取。所以users的请求是这样的：

Request URL:https://localhost:8443/users
    Request Method:GET
    Status Code:200 
    Remote Address:127.0.0.1:8888
    
    **Response Headers**
    view source
    Cache-Control:no-cache, no-store, max-age=0, must-revalidate
    Content-Type:application/json;charset=UTF-8
    Date:Thu, 08 Sep 2016 14:31:33 GMT
    Expires:0
    Pragma:no-cache
    Strict-Transport-Security:max-age=31536000 ; includeSubDomains
    Transfer-Encoding:chunked
    X-Application-Context:application:dev:8443
    X-Content-Type-Options:nosniff
    X-Frame-Options:DENY
    X-XSS-Protection:1; mode=block
    
    **Request Headers**
    view source
    Accept:text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
    Accept-Encoding:gzip, deflate, sdch, br
    Accept-Language:zh-CN,zh;q=0.8
    Authorization:Basic YWRtaW46dGVzdA==
    Connection:keep-alive
    Host:localhost:8443
    Upgrade-Insecure-Requests:1
    User-Agent:Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/52.0.2743.82 Safari/537.36

redirect的另一个作用是原请求的内容将会被舍弃，即如果是post请求，redirect的时候默认是不带参数的。与之相对应的forward的请求是转发，只有一次请求，并且带body转发过去。

--------------------

# Http 303 #

303 See Other。通常是指所请求的资源在别的地方，并且同302一样，会在header中的location标明资源的位置。在我的一个是使用过程中，我想要创建一个user，当关于这个user的key已经存在的时候，server将返回303，并且告之这个user的获取位置。

**Example**  
Client request:

> POST / HTTP/1.1  
> Host: www.example.com

Server response:

> HTTP/1.1 303 See Other  
> Location: [http://example.org/other][http_example.org_other]

## 实验 ##

我将要发送post请求创建user，如果user已经存在则返回303

Map<String, Double> users = new HashMap<>(); @ResponseBody @RequestMapping(value = "/users", method = RequestMethod.POST) public ResponseEntity createUser(String username){ Double luckNum = users.get(username); if (luckNum ==null){ double random = Math.random(); users.put(username, random); return new ResponseEntity(random,HttpStatus.OK); }else{ MultiValueMap<String,String> headers = new HttpHeaders(); headers.add("Location", "/users/"+username); return new ResponseEntity(luckNum, headers, HttpStatus.SEE_OTHER); } } @ResponseBody @RequestMapping(value = "/users/{username}", method = RequestMethod.GET) public ResponseEntity getUser(@PathVariable("username") String username){ ResponseEntity responseEntity = new ResponseEntity("I'm user, My name is "+ username+ " And my luck num is "+users.get(username), HttpStatus.OK); return responseEntity; }

**发送**  
![686418-20160908230930207-909758310.png][]

**查看拦截**  
![686418-20160908230935926-1218749076.png][]

可以看到，post的时候返回303，并且在返回的response的header中添加了：

> Location: /users/test

所以see other的意思就是去别的地方看看。值得注意的是，如果返回303，但是没有添加location,那么只会查看一条请求303.而在httpclient的默认处理中，这时候会抛出exception：location not found。

### 参考 ###

*  [维基百科 http 302][http 302]
 *  [维基百科 http 303][http 303]

[http_www.iana.org_domains_example]: http://www.iana.org/domains/example/
[686418-20160908223534363-1357573526.png]: /images/20220716/0ed8179be25f43c394d317fabfcec3b8.png
[https_localhost_8443_users]: https://localhost:8443/users
[http_example.org_other]: http://example.org/other
[686418-20160908230930207-909758310.png]: /images/20220716/bbcd23726e274481a4b2095111bc373c.png
[686418-20160908230935926-1218749076.png]: /images/20220716/e632a051b41e4ab0b3094a5c48fa625d.png
[http 302]: https://en.wikipedia.org/wiki/HTTP_302
[http 303]: https://en.wikipedia.org/wiki/HTTP_303