在删除请求中使用主体的一个原因是为了进行乐观并发控制。

你读了唱片的第一个版本。

GET /some-resource/1
200 OK { id:1, status:"unimportant", version:1 }

你的同事读了记录的第一个版本。

GET /some-resource/1
200 OK { id:1, status:"unimportant", version:1 }

你的同事更改了记录并更新了数据库，数据库将版本更新为2:

PUT /some-resource/1 { id:1, status:"important", version:1 }
200 OK { id:1, status:"important", version:2 }

你试着删除记录:

DELETE /some-resource/1 { id:1, version:1 }
409 Conflict

您应该得到一个乐观锁异常。重新阅读记录，确认它的重要性，也许不要删除它。

使用它的另一个原因是一次删除多条记录(例如，具有行选择复选框的网格)。

DELETE /messages
[{id:1, version:2},
{id:99, version:3}]
204 No Content

注意，每个消息都有自己的版本。也许您可以使用多个头文件指定多个版本，但对于George来说，这更简单、更方便。

这适用于Tomcat(7.0.52)和Spring MVC(4.05)，可能也适用于更早的版本:

@RestController
public class TestController {

    @RequestMapping(value="/echo-delete", method = RequestMethod.DELETE)
    SomeBean echoDelete(@RequestBody SomeBean someBean) {
        return someBean;
    }
}

2014年更新的HTTP 1.1规范(RFC 7231)明确地允许在DELETE请求中使用实体:

DELETE请求消息中的有效负载没有定义的语义;在DELETE请求上发送有效负载主体可能会导致某些现有实现拒绝该请求。

有些版本的Tomcat和Jetty似乎会忽略存在的实体体。如果你想要收到它，那就麻烦了。

Roy Fielding在HTTP邮件列表上澄清了HTTP邮件列表https://lists.w3.org/Archives/Public/ietf-http-wg/2020JanMar/0123.html并说:

GET/DELETE主体绝对禁止产生任何影响 对请求的处理或解释

这意味着主体不能修改服务器的行为。 然后他补充道:

除了 为了维护，必须读取和丢弃接收到的字节 信息框架。

最后是不禁止尸体的原因

我们不禁止派人去的唯一原因是 因为这将导致懒惰的实现，假设没有人会这样做 被发送。

因此，当客户端可以发送有效负载主体时，服务器应该丢弃它 和api不应该为这些请求的有效载荷体定义语义。

在我看来，RFC 2616并没有规定这一点。

从第4.3节开始:

The presence of a message-body in a request is signaled by the inclusion of a Content-Length or Transfer-Encoding header field in the request's message-headers. A message-body MUST NOT be included in a request if the specification of the request method (section 5.1.1) does not allow sending an entity-body in requests. A server SHOULD read and forward a message-body on any request; if the request method does not include defined semantics for an entity-body, then the message-body SHOULD be ignored when handling the request.

9.7节:

The DELETE method requests that the origin server delete the resource identified by the Request-URI. This method MAY be overridden by human intervention (or other means) on the origin server. The client cannot be guaranteed that the operation has been carried out, even if the status code returned from the origin server indicates that the action has been completed successfully. However, the server SHOULD NOT indicate success unless, at the time the response is given, it intends to delete the resource or move it to an inaccessible location. A successful response SHOULD be 200 (OK) if the response includes an entity describing the status, 202 (Accepted) if the action has not yet been enacted, or 204 (No Content) if the action has been enacted but the response does not include an entity. If the request passes through a cache and the Request-URI identifies one or more currently cached entities, those entries SHOULD be treated as stale. Responses to this method are not cacheable.c

因此，它没有显式地允许或禁止，并且代理可能会删除消息体(尽管它应该读取并转发它)。

只是一个提示，如果你在你的DELETE请求中提供了一个主体，并且使用了谷歌云HTTPS负载均衡器，它将拒绝你的请求，错误为400。我的头撞到墙上，然后发现谷歌，不管出于什么原因，认为一个带有主体的DELETE请求是一个畸形的请求。