Networking - Java Examples in a Nutshell - page 108

Example 5•9: Server.java (continued)
* constructor to create a thread to handle the connection. Connection
* objects are created by Listener threads. These threads are part of
* the server's ThreadGroup, so all Connection threads are part of that
* group, too.
**/
public Connection(Socket client, Service service) {
super("Server.Connection:" +
client.getInetAddress().getHostAddress() +
":" + client.getPort());
this.client = client;
this.service = service;
}
/**
* This is the body of each and every Connection thread.
* All it does is pass the client input and output streams to the
* serve() method of the specified Service object. That method is
* responsible for reading from and writing to those streams to
* provide the actual service. Recall that the Service object has
* been passed from the Server.addService() method to a Listener
* object to the addConnection() method to this Connection object, and
* is now finally being used to provide the service. Note that just
* before this thread exits it always calls the endConnection() method
* to remove itself from the set of connections
**/
public void run() {
try {
InputStream in = client.getInputStream();
OutputStream out = client.getOutputStream();
service.serve(in, out);
}
catch (IOException e) {log(e);}
finally { endConnection(this); }
}
}
/**
* Here is the Service interface that we have seen so much of. It defines
* only a single method which is invoked to provide the service. serve()
* will be passed an input stream and an output stream to the client. It
* should do whatever it wants with them, and should close them before
* returning.
*
* All connections through the same port to this service share a single
* Service object. Thus, any state local to an individual connection must
* be stored in local variables within the serve() method. State that
* should be global to all connections on the same port should be stored
* in instance variables of the Service class. If the same Service is
* running on more than one port, there will typically be different
* Service instances for each port. Data that should be global to all
* connections on any port should be stored in static variables.
*
* Note that implementations of this interface must have a no-argument
* constructor if they are to be dynamically instantiated by the main()
* method of the Server class.
**/
public interface Service {
public void serve(InputStream in, OutputStream out) throws IOException;