URLConnections - Java Network Programming - page 197

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There was no Content-length header. Many servers don't bother to provide a Content-
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a binary file. Here's the HTTP header you get when you request the GIF image http://
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2294:
% java HeaderViewer http://oreilly.com/favicon.ico
Content-type: image/x-icon
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Retrieving Arbitrary Header Fields
The last six methods requested specific fields from the header, but there's no theoretical
limit to the number of header fields a message can contain. The next five methods inspect
arbitrary fields in a header. Indeed, the methods of the preceding section are just thin
wrappers over the methods discussed here; you can use these methods to get header
fields that Java's designers did not plan for. If the requested header is found, it is returned.
Otherwise, the method returns null .
public String getHeaderField(String name)
The getHeaderField() method returns the value of a named header field. The name
of the header is not case sensitive and does not include a closing colon. For example, to
get the value of the Content-type and Content-encoding header fields of a URLConnec
tion object uc , you could write:
String contentType = uc . getHeaderField ( "content-type" );
String contentEncoding = uc . getHeaderField ( "content-encoding" ));
To get the Date, Content-length, or Expires headers, you'd do the same:
String data = uc . getHeaderField ( "date" );
String expires = uc . getHeaderField ( "expires" );
String contentLength = uc . getHeaderField ( "Content-length" );
These methods all return String , not int or long as the getContentLength() , getEx
pirationDate() , getLastModified() , and getDate() methods that the preceding sec‐
tion did. If you're interested in a numeric value, convert the String to a long or an int .