Java Network Programming, Second Edition

The ContentHandlerFactory Interface

A ContentHandlerFactory defines the rules for where ContentHandler classes are stored. Create a class that implements ContentHandlerFactory, and give this class a createContentHandler( ) method that knows how to instantiate your ContentHandler. The createContentHandler( ) method should return null if it can’t find a ContentHandler appropriate for a MIME type; null signals Java to look for ContentHandler classes in the default locations. When your application starts, call the URLConnection’s setContentHandlerFactory( ) method to set the ContentHandlerFactory. This method may be called only once in the lifetime of an application.

The createContentHandler( ) Method

Just as the createURLStreamHandler( ) method of the URLStreamHandlerFactory interface was responsible for finding and loading the appropriate protocol handler, so too the createContentHandler( ) method of the ContentHandlerFactory interface is responsible for finding and loading the appropriate ContentHandler given a MIME type:

public abstract ContentHandler createContentHandler(String mimeType)

This method should be called only by the getContent( ) method of a URLConnection object. For instance, Example 17.7 is a ContentHandlerFactory that knows how to find the right handler for the text/tab-separated-values content handler of Example 17.1:

Example 17-7. TabFactory

package com.macfaq.net.www.content; import java.net.*; public class TabFactory implements ContentHandlerFactory { public ContentHandler ...