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
更有可能是400个坏请求
[* * 6.5.1。400错误请求**][1]
400(坏请求)状态代码表示服务器不能或 将不会处理请求由于某些东西被认为是 客户端错误(例如，格式错误的请求语法，无效的请求 消息框架，或欺骗性请求路由)。
由于请求包含重复的值(已经存在的值)，因此可以将其视为客户机错误。需要在下次尝试之前更改请求。 通过考虑这些事实，我们可以得出HTTP STATUS 400错误请求的结论。
其他回答
根据RFC 7231，如果POST处理的结果等同于 现有资源的表示。
I think for REST, you just have to make a decision on the behavior for that particular system in which case, I think the "right" answer would be one of a couple answers given here. If you want the request to stop and behave as if the client made a mistake that it needs to fix before continuing, then use 409. If the conflict really isn't that important and want to keep the request going, then respond by redirecting the client to the entity that was found. I think proper REST APIs should be redirecting (or at least providing the location header) to the GET endpoint for that resource following a POST anyway, so this behavior would give a consistent experience.
EDIT: It's also worth noting that you should consider a PUT since you're providing the ID. Then the behavior is simple: "I don't care what's there right now, put this thing there." Meaning, if nothing is there, it'll be created; if something is there it'll be replaced. I think a POST is more appropriate when the server manages that ID. Separating the two concepts basically tells you how to deal with it (i.e. PUT is idempotent so it should always work so long as the payload validates, POST always creates, so if there is a collision of IDs, then a 409 would describe that conflict).
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。
错误402，需要付款
例如，这个资源已经存在，但如果你给我足够的钱，我会删除当前的一个，给你:D
.．.但是看看mozilla在https://developer.mozilla.org/en-US/docs/Web/HTTP/Status#client_error_responses上对状态码的定义
作为一个更严肃的答案，这里没有人提供，那451呢:由于法律原因无法使用。你不能“合法地(通过你自己制定的条款和条件)”让多人访问相同的帐户信息
422也是一个很好的选择，它是不可处理的实体 请求格式良好，但由于语义错误而无法执行。由于它是一个完全有效的请求，但由于它在语义上与另一个条目相等，所以不能遵循它。
在检查重复记录的正确代码时偶然发现了这个问题。
请原谅我的无知，但我不明白为什么每个人都忽略了代码“300”，它清楚地表示“多项选择”或“模棱两可”
在我看来，这将是构建非标准或特定系统供自己使用的完美代码。我也可能是错的!
https://www.rfc-editor.org/rfc/rfc7231#section-6.4.1
