Getting A File's Mime Type In Java
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?
在Java 7中，您现在可以使用Files.probeContentType(path) 。
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, eg, Mime-Util (which is a great library, using both file extension and content).
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);
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