title: problem with protected method in spring using MappingMediaTypeFileExtensionResolver
body: <p>I'm having a doubt using this class in SpringBoot application <strong>MappingMediaTypeFileExtensionResolver</strong>,
  i want get the mediatype form file extension but the only method that i need is protected (
  <strong>lookupMediaType(String extension)</strong> )
  I can implement the method directly but Im looking for a better solution.</p>
  
  <pre><code>Map&lt;String, MediaType&gt; mapping =  new HashMap&lt;String, MediaType&gt;();
  mapping.put("PDF", MediaType.APPLICATION_PDF);
  mapping.put("TEXT", MediaType.TEXT_PLAIN);
  MappingMediaTypeFileExtensionResolver resolver = new MappingMediaTypeFileExtensionResolver(mapping);
  
  
  this.fileType = resolver.lookupMediaType("JSON"); 
  </code></pre>
  
  <p>how can i access it if Im in another package?</p>