Java Network programming Question:

Each connection is handled by the run( ) method of the RequestProcessor class shown in Example. This method waits until it can get a Socket out of the pool. Once it does that, it gets input and output streams from the socket and chains them to a reader and a writer. The reader reads the first line of the client request to determine the version of HTTP that the client supports--we want to send a MIME header only if this is HTTP 1.0 or later--and what file is requested. Assuming the method is GET, the file that is requested is converted to a filename on the local filesystem. If the file requested was a directory (i.e., its name ended with a slash), we add the name of an index file. We use the canonical path to make sure that the requested file doesn't come from outside the document root directory. Otherwise, a sneaky client could walk all over the local filesystem by including .. in URLs to walk up the directory hierarchy. This is all we'll need from the client, though a more advanced web server, especially one that logged hits, would read the rest of the MIME header the client sends.

Next the requested file is opened and its contents are read into a byte array. If the HTTP version is 1.0 or later, we write the appropriate MIME headers on the output stream. To figure out the content type, we call the guessContentTypeFromName( ) method to map file extensions such as .html onto MIME types such as text/html. The byte array containing the file's contents is written onto the output stream, and the connection is closed. Exceptions may be thrown at various places if, for example, the file cannot be found or opened. If an exception occurs, we send an appropriate HTTP error message to the client instead of the file's contents