title: SprintBoot Content-type as null
body: <p>I have a springboot application which implements a PUT method.
  The client side is send the PUT request to my application but the Header "Content-type" is null... in fact, the client is not sending the "Content-type", so  SpringBoot is actually rejecting this request because it cannot handle null content-type.</p>
  
  <pre><code>13:24:13.658 [http-nio-8080-exec-3] DEBUG vlet.mvc.method.annotation.ExceptionHandlerExceptionResolver - Resolving exception from handler [null]: org.springframework.web.HttpMediaTypeNotSupportedException: Content type 'null' not supported
  </code></pre>
  
  <p>Is there a way which I can make SpringBoot to accept a null Content-type and make it to assume some default content-type value?</p>
  
  <p>The controller looks like:</p>
  
  <pre><code>@RequestMapping(value="/xxxx", method = RequestMethod.PUT, produces = MediaType.APPLICATION_JSON_VALUE, consumes = MediaType.TEXT_PLAIN_VALUE)
  @ApiResponses(value = {@ApiResponse(code=200, message="OK", response=yyyyyyyy.class)})
  public ResponseEntity&lt;?&gt; xxxxxx(@RequestBody String s)
  </code></pre>
  
  <p>so the idea is to consume a plan text and produces as response a json object.</p>