Java Network Programming, Second Edition

The ContentHandler Class

A subclass of ContentHandler overrides the getContent( ) method to return an object that’s the Java equivalent of the content. This method can be quite simple or quite complex, depending almost entirely on the complexity of the content type you’re trying to parse. A text/plain content handler is quite simple; a text/rtf content handler would be very complex.

The ContentHandler class has only a simple noargs constructor:

public ContentHandler(  )

Since ContentHandler is an abstract class, you never call its constructor directly, only from inside the constructors of subclasses.

The primary method of the class, albeit an abstract one, is getContent( ) :

public abstract Object getContent(URLConnection uc) throws IOException

This method is normally called only from inside the getContent( ) method of a URLConnection object. It is overridden in a subclass that is specific to the type of content being handled. getContent( ) should use the URLConnection’s InputStream to create an object. There are no rules about what type of object a content handler should return. In general, this depends on what the application requesting the content expects. Content handlers for text-like content bundled with the JDK return some subclass of InputStream. Content handlers for images return ImageProducer objects.

The getContent( ) method of a content handler does not get the full InputStream that the URLConnection has access to. The InputStream that a content handler sees should include ...