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Detecting MIME types of a file

 
Greenhorn
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How can the MIME type of a file be known on the basis of its contents?
I don't want the detection to be based on file's extension as new extensions evolve everyday.
 
Bartender
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I don't think there is a reliable way. Some files, like JPG images, have a header one could read. Others, like plain text files, do not.
The only programmatic way I know of is ServletContext.getMimeType, but that relies on the container configuration, which in turn relies on web.xml, which contains a map of file extensions to mime types.
 
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