The only reason that I can think of is if you have a directory that contains files of some type (lets say pdf) which are directly server to the browser, then the container will automatically set the content type of the response for the files (example application/pdf for pdf files)...
Does it mean that for a particular type of the file (ex.PDF) the type of the response is changed by the container if it is set in <mime-mapping> tag for that extension.
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