这里的主要问题是路径 "/test.htm" 在检查值之前将首先使用内容协商Accept 标头.对于像 *.htm 这样的扩展，Spring 将使用 org.springframework.web.accept.ServletPathExtensionContentNegotiationStrategy 并解析返回的可接受媒体类型是 text/html 与 MappingJacksonHttpMessageConverter 产生的不匹配，即.application/json 因此返回 406.

The main issue here is that the path "/test.htm" is going to use content negotiation first before checking the value of an Accept header. With an extension like *.htm, Spring will use a org.springframework.web.accept.ServletPathExtensionContentNegotiationStrategy and resolve that the acceptable media type to return is text/html which does not match what MappingJacksonHttpMessageConverter produces, ie. application/json and therefore a 406 is returned.

简单的解决方案是将路径更改为类似 /test 的内容，其中基于路径的内容协商不会为响应解析任何内容类型.相反，基于标头的不同 ContentNegotiationStrategy 将解析 Accept 标头的值.

The simple solution is to change the path to something like /test, in which content negotiation based on the path won't resolve any content type for the response. Instead, a different ContentNegotiationStrategy based on headers will resolve the value of the Accept header.

复杂的解决方案是更改在处理您的 @ResponseBody 的 RequestResponseBodyMethodProcessor 中注册的 ContentNegotiationStrategy 对象的顺序.

The complicated solution is to change the order of the ContentNegotiationStrategy objects registered with the RequestResponseBodyMethodProcessor which handles your @ResponseBody.