不允许部分PUT背后的理由是什么？ [英] What's the justification behind disallowing partial PUT?

问题描述

为什么HTTP PUT请求必须包含整体状态的表示而不能仅仅是部分？

Why does an HTTP PUT request have to contain a representation of a 'whole' state and can't just be a partial?

我知道这是PUT的现有定义 - 这个问题是关于为什么这样定义的原因。

I understand that this is the existing definition of PUT - this question is about the reason(s) why it would be defined that way.

ie：

通过阻止部分PUT获得了什么？

What is gained by preventing partial PUTs?

为什么阻止幂等部分更新被视为可接受的损失？

Why was preventing idempotent partial updates considered an acceptable loss?

推荐答案

PUT表示HTTP规范定义的含义。客户端和服务器无法改变这种含义。如果客户端或服务器以与其定义相矛盾的方式使用PUT，则至少可能发生以下情况：

PUT means what the HTTP spec defines it to mean. Clients and servers cannot change that meaning. If clients or servers use PUT in a way that contradicts its definition, at least the following thing might happen:

根据定义，Put是幂等的。这意味着客户端（或中间人！）可以重复任何次数的PUT，并确保效果相同。假设中间设备从客户端接收PUT请求。当它将请求转发到服务器时，存在网络问题。中间人根据定义知道它可以重试PUT直到它成功。如果服务器以非幂等方式使用PUT，则这些潜在的多个调用将产生不良影响。

Put is by definition idempotent. That means a client (or intermediary!) can repeat a PUT any number of times and be sure that the effect will be the same. Suppose an intermediary receives a PUT request from a client. When it forwards the request to the server, there is a network problem. The intermediary knows by definition that it can retry the PUT until it succeeds. If the server uses PUT in a non idempotent way these potential multiple calls will have an undesired effect.

如果要进行部分更新，请使用PATCH或使用POST一个子资源并返回303参见其他'主'资源，例如

If you want to do a partial update, use PATCH or use POST on a sub-resource and return 303 See Other to the 'main' resource, e.g.

POST /account/445/owner/address
Content-Type: application/x-www-form-urlencoded

street=MyWay&zip=22222&city=Manchaster


303 See Other
Location: /account/445

编辑：关于一般问题为什么部分更新不能是幂等的：

On the general question why partial updates cannot be idempotent:

部分更新通常不能是幂等的，因为幂等性取决于媒体类型语义。 IOW，您可能能够指定允许幂等补丁的格式，但不能保证PATCH在每种情况下都是幂等的。由于方法的语义不能是媒体类型的函数（出于正交原因），PATCH需要被定义为非幂等的。并且PUT（被定义为幂等）不能用于部分更新。

A partial update cannot be idempotent in general because the idempotency depends on the media type semantics. IOW, you might be able to specify a format that allows for idempotent patches, but PATCH cannot be guaranteed to be idempotent for every case. Since the semantics of a method cannot be a function of the media type (for orthogonality reasons) PATCH needs to be defined as non-idempotent. And PUT (being defined as idempotent) cannot be used for partial updates.

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