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

This is the simplest way I found for doing this:

byte[] byteArray = ...
InputStream is = new BufferedInputStream(new ByteArrayInputStream(byteArray));
String mimeType = URLConnection.guessContentTypeFromStream(is);

Answer 2

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);

Answer 3

If you are stuck with java 5-6 then this utility class from servoy open source product.

You only need this function

public static String getContentType(byte[] data, String name)

It probes the first bytes of the content and returns the content types based on that content and not by file extension.

Answer 4

In Java 7 you can now just use Files.probeContentType(path).

Answer 5

I tried several ways to do it, including the first ones said by @Joshua Fox. But some don't recognize frequent mimetypes like for PDF files, and other could not be trustable with fake files (I tried with a RAR file with extension changed to TIF). The solution I found, as also is said by @Joshua Fox in a superficial way, is to use MimeUtil2, like this:

MimeUtil2 mimeUtil = new MimeUtil2();
mimeUtil.registerMimeDetector("eu.medsea.mimeutil.detector.MagicMimeMimeDetector");
String mimeType = MimeUtil2.getMostSpecificMimeType(mimeUtil.getMimeTypes(file)).toString();

Answer 6

With Apache Tika you need only three lines of code:

File file = new File("/path/to/file");
Tika tika = new Tika();
System.out.println(tika.detect(file));

If you have a groovy console, just paste and run this code to play with it:

@Grab('org.apache.tika:tika-core:1.14')
import org.apache.tika.Tika;

def tika = new Tika()
def file = new File("/path/to/file")
println tika.detect(file)

Keep in mind that its APIs are rich, it can parse "anything". As of tika-core 1.14, you have:

String  detect(byte[] prefix)
String  detect(byte[] prefix, String name)
String  detect(File file)
String  detect(InputStream stream)
String  detect(InputStream stream, Metadata metadata)
String  detect(InputStream stream, String name)
String  detect(Path path)
String  detect(String name)
String  detect(URL url)

See the apidocs for more information.