Getting the correct MIME type of a file in Java

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I read that Files.probeContentType(path) can be used to get the file type of a file without relying on file extensions. However in my case, if I remove the file type, the function returns the file type "null". If I attach the correct extension, then I get the type as "image/jpeg". Can anyone what is going on here or is my understanding of probeContentType not correct? I'm expecting it to return "image/jpeg" irrespective of the fact that it has file extension or not.

This is the case where I deliberately removed the extension from the file "Nature.jpg":

enter image description here

Update Using org.apache.tika (v2.4)

Tika tika = new Tika();
String myType = tika.detect(filePath);

If the file extension is not present I get the filetype as "application/octet-stream". The image is originally jpeg so I was expecting it to detect it as an image.

mime-types java
1 Answers

While it might not rely on the file extension in all implementations, it might use it in others. According to Oracle - "The implementation of this method is highly platform specific and is not infallible."

"The means by which a file type detector determines the file type is highly implementation specific. A simple implementation might examine the file extension (a convention used in some platforms) and map it to a file type. In other cases, the file type may be stored as a file attribute or the bytes in a file may be examined to guess its file type." - https://docs.oracle.com/javase/8/docs/api/java/nio/file/spi/FileTypeDetector.html

You can try Apache Tika as an alternative, I've had good experiences with it - https://tika.apache.org/

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