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重定向Http status code 303 和 302

news 来源：原创 2024/5/9 1:32:32

http 302
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/

实验

首先，我们用一个Map来存储信息，key为username，value为随机数。
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：

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
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

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;
    }

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