我正在构建一个允许客户端存储对象的服务器。这些对象是在客户端完全构造的，对象id在对象的整个生命周期内都是永久的。
我已经定义了API，以便客户端可以使用PUT创建或修改对象:
PUT /objects/{id} HTTP/1.1
...
{json representation of the object}
{id}是对象id，所以它是Request-URI的一部分。
现在，我也在考虑允许客户端使用POST创建对象:
POST /objects/ HTTP/1.1
...
{json representation of the object, including ID}
由于POST意味着“追加”操作，我不确定在对象已经存在的情况下该做什么。我应该把请求作为修改请求，还是应该返回一些错误代码(哪个)?
当前回答
我会选择422不可处理实体，当请求无效时使用，但问题不在于语法或身份验证。
作为反对其他答案的论据，使用任何非4xx错误代码将暗示它不是客户端错误，而它显然是。使用非4xx错误代码来表示客户端错误完全没有意义。
It seems that 409 Conflict is the most common answer here, but, according to the spec, that implies that the resource already exists and the new data you are applying to it is incompatible with its current state. If you are sending a POST request, with, for example, a username that is already taken, it's not actually conflicting with the target resource, as the target resource (the resource you're trying to create) has not yet been posted. It's an error specifically for version control, when there is a conflict between the version of the resource stored and the version of the resource requested. It's very useful for that purpose, for example when the client has cached an old version of the resource and sends a request based on that incorrect version which would no longer be conditionally valid. "In this case, the response representation would likely contain information useful for merging the differences based on the revision history." The request to create another user with that username is just unprocessable, having nothing to do with any version conflict.
为了记录，422也是GitHub使用的状态码，当您尝试按已使用的名称创建存储库时。
其他回答
也许是在游戏后期，但我在尝试创建REST API时偶然发现了这个语义问题。
为了稍微扩展一下wrkken的回答，我认为您可以根据情况使用409 Conflict或403 Forbidden -简而言之，当用户完全无法解决冲突并完成请求时使用403错误(例如，他们不能发送DELETE请求来显式删除资源)，或者如果可能做一些事情，则使用409。
10.4.4禁止403 服务器理解请求，但拒绝执行。 授权没有帮助，请求不应该重复。如果 请求方法不是HEAD，服务器希望公开 为什么要求没有被满足，它应该描述原因 对于实体中的拒绝。如果服务器不希望做出 此信息可用于客户端，状态代码404(不是 Found)可以代替。
现在，有人说“403”，就会想到权限或身份验证问题，但规范说，这基本上是服务器告诉客户端它不会这样做，不要再问了，这就是客户端不应该这样做的原因。
至于PUT vs. POST…当用户没有办法或不应该为资源创建标识符时，POST应该用于创建资源的新实例。当资源的标识已知时，使用PUT。
9.6 PUT ... The fundamental difference between the POST and PUT requests is reflected in the different meaning of the Request-URI. The URI in a POST request identifies the resource that will handle the enclosed entity. That resource might be a data-accepting process, a gateway to some other protocol, or a separate entity that accepts annotations. In contrast, the URI in a PUT request identifies the entity enclosed with the request -- the user agent knows what URI is intended and the server MUST NOT attempt to apply the request to some other resource. If the server desires that the request be applied to a different URI, it MUST send a 301 (Moved Permanently) response; the user agent MAY then make its own decision regarding whether or not to redirect the request.
另一个潜在的治疗方法是使用PATCH。PATCH被定义为改变内部状态的东西，不局限于追加。
PATCH将通过允许您更新已经存在的项目来解决这个问题。参见:RFC 5789: PATCH
我会选择422不可处理实体，当请求无效时使用，但问题不在于语法或身份验证。
作为反对其他答案的论据，使用任何非4xx错误代码将暗示它不是客户端错误，而它显然是。使用非4xx错误代码来表示客户端错误完全没有意义。
It seems that 409 Conflict is the most common answer here, but, according to the spec, that implies that the resource already exists and the new data you are applying to it is incompatible with its current state. If you are sending a POST request, with, for example, a username that is already taken, it's not actually conflicting with the target resource, as the target resource (the resource you're trying to create) has not yet been posted. It's an error specifically for version control, when there is a conflict between the version of the resource stored and the version of the resource requested. It's very useful for that purpose, for example when the client has cached an old version of the resource and sends a request based on that incorrect version which would no longer be conditionally valid. "In this case, the response representation would likely contain information useful for merging the differences based on the revision history." The request to create another user with that username is just unprocessable, having nothing to do with any version conflict.
为了记录，422也是GitHub使用的状态码，当您尝试按已使用的名称创建存储库时。
我的感觉是409冲突是最合适的，但是，在野外当然很少见到:
The request could not be completed due to a conflict with the current state of the resource. This code is only allowed in situations where it is expected that the user might be able to resolve the conflict and resubmit the request. The response body SHOULD include enough information for the user to recognize the source of the conflict. Ideally, the response entity would include enough information for the user or user agent to fix the problem; however, that might not be possible and is not required. Conflicts are most likely to occur in response to a PUT request. For example, if versioning were being used and the entity being PUT included changes to a resource which conflict with those made by an earlier (third-party) request, the server might use the 409 response to indicate that it can't complete the request. In this case, the response entity would likely contain a list of the differences between the two versions in a format defined by the response Content-Type.
在您的情况下，您可以使用409冲突
如果你想检查另一个HTTPs状态码从下面的列表
1××信息
100 Continue
101 Switching Protocols
102 Processing
2××成功
200 OK
201 Created
202 Accepted
203 Non-authoritative Information
204 No Content
205 Reset Content
206 Partial Content
207 Multi-Status
208 Already Reported
226 IM Used
3××重定向
300 Multiple Choices
301 Moved Permanently
302 Found
303 See Other
304 Not Modified
305 Use Proxy
307 Temporary Redirect
308 Permanent Redirect
4××客户端错误
400 Bad Request
401 Unauthorized
402 Payment Required
403 Forbidden
404 Not Found
405 Method Not Allowed
406 Not Acceptable
407 Proxy Authentication Required
408 Request Timeout
409 Conflict
410 Gone
411 Length Required
412 Precondition Failed
413 Payload Too Large
414 Request-URI Too Long
415 Unsupported Media Type
416 Requested Range Not Satisfiable
417 Expectation Failed
418 I’m a teapot
421 Misdirected Request
422 Unprocessable Entity
423 Locked
424 Failed Dependency
426 Upgrade Required
428 Precondition Required
429 Too Many Requests
431 Request Header Fields Too Large
444 Connection Closed Without Response
451 Unavailable For Legal Reasons
499 Client Closed Request
5××服务器错误
500 Internal Server Error
501 Not Implemented
502 Bad Gateway
503 Service Unavailable
504 Gateway Timeout
505 HTTP Version Not Supported
506 Variant Also Negotiates
507 Insufficient Storage
508 Loop Detected
510 Not Extended
511 Network Authentication Required
599 Network Connect Timeout Error
