Getting A File's Mime Type In Java

Question

I was just wondering how most people fetch a mime type from a file in Java? So far I've tried two utils: JMimeMagic & Mime-Util. The first gave me memory exceptions, the second doesn't close its streams off properly. I was just wondering if anyone else had a method/library that they used and worked correctly?

Answer 1

Getting A File’s Mime Type In Java

Answer 2

Thanks - I saw that article. It's where I got the links from both of the library's that I have tried. Trouble is both of them have got problems and the other methods mentioned are either too slow, too restrictive or overkill. I was hoping someone else might have found something newer.

Answer 3

Unfortunately,

mimeType = file.toURL().openConnection().getContentType();

does not work, since this use of URL leaves a file locked, so that, for example, it is undeletable.

However, you have this:

mimeType= URLConnection.guessContentTypeFromName(file.getName());

and also the following, which has the advantage of going beyond mere use of file extension, and takes a peek at content

InputStream is = new BufferedInputStream(new FileInputStream(file));
mimeType = URLConnection.guessContentTypeFromStream(is);
 //...close stream

However, as suggested by the comment above, the built-in table of mime-types is quite limited, not including, for example, MSWord and PDF. So, if you want to generalize, you'll need to go beyond the built-in libraries, using, e.g., Mime-Util (which is a great library, using both file extension and content).

Answer 4

The JAF API is part of JDK 6. Look at javax.activation package.

Most interesting classes are javax.activation.MimeType - an actual MIME type holder - and javax.activation.MimetypesFileTypeMap - class whose instance can resolve MIME type as String for a file:

String fileName = "/path/to/file";
MimetypesFileTypeMap mimeTypesMap = new MimetypesFileTypeMap();

// only by file name
String mimeType = mimeTypesMap.getContentType(fileName);

// or by actual File instance
File file = new File(fileName);
mimeType = mimeTypesMap.getContentType(file);