Presents your 
JAVA E-NEWSLETTER for September 30, 2002

<------------------------------------------->

DISCOVER MIMETYPE

When returning content from a servlet or jsp page other than HTML, you
need to know the Multipart Internet Mail Extension (MIME) type. Often 
you
have to hard-code the information--but is there a better way?

Although it doesn't support all the types you're likely to need, Java
does provide automatic filename-to-MIME type mapping. The mapping is 
hidden
within an interface called FileNameMap, which you can find in the
java.net package. The map is obtained via the URLConnection class found 
in the
same package. Once the map is obtained, getContentTypeFor is the only
method available. By passing in a filename, the MIME type for that 
extension
can be determined.

Here's some simple example code:

import java.net.*;

public class FilenameMap {

    static public void main(String[] args) {
        FileNameMap map = URLConnection.getFileNameMap();
        System.err.println(""+map.getContentTypeFor("blah.exe"));
        System.err.println(""+map.getContentTypeFor("blah.gif"));
        System.err.println(""+map.getContentTypeFor("blah.png"));
        System.err.println(""+map.getContentTypeFor("blah.jpeg"));
        System.err.println(""+map.getContentTypeFor("blah.doc"));
        System.err.println(""+map.getContentTypeFor("blah.xml"));
        System.err.println(""+map.getContentTypeFor("blah.html"));
        System.err.println(""+map.getContentTypeFor("blah.jsp"));
        System.err.println(""+map.getContentTypeFor("blah.tiff"));
    }

}

The code above returns the following values. Note that not all file
extensions are known.

application/octet-stream
image/gif
image/png
image/jpeg
null
application/xml
text/html
null
image/tiff

----------------------------------------