Question

I am writing a server like below

public class Server<T extends RequestHandler> {

    public void start() {

        try{
            this.serverSocket = new ServerSocket(this.port, this.backLog);
        } catch (IOException e) {
            LOGGER.error("Could not listen on port " + this.port, e);
            System.exit(-1);
        }

        while (!stopTheServer) {
            socket = null;
            try {
                socket = serverSocket.accept();
                handleNewConnectionRequest(socket);
            } catch (IOException e) {
                LOGGER.warn("Accept failed at: " + this.port, e);
                e.printStackTrace();
            }
        }

    }

    protected void handleNewConnectionRequest(Socket socket) {
        try {
            executorService.submit(new T(socket));
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

But in the handleNewConnectionRequest(...) method, I can’t create an instance of T as it is actually not a class. Also I can’t use the method mentioned here as I want to pass the socket instance so that the request handler can get OutputStream and InputStream on the socket.

---

Can’t I make a generic server like above and have different protocol handlers e.g

public class HttpRequestHandler extends RequestHandler {
    ...
}

public class FtpRequestHandler extends RequestHandler {
    ...
}

public class SmtpRequestHandler extends RequestHandler {
    ...
}

and then use them like below

Server<HttpRequestHandler> httpServer = new Server<HttpRequestHandler>();
Server<FtpRequestHandler> ftpServer = new Server<FtpRequestHandler >();
Server<SmtpRequestHandler> smtpServer = new Server<SmtpRequestHandler >();

Answer 1

Maybe make different Server subclasses befitting various handler types. One example:

public class HttpServer extends Server<HttpRequestHandler> {

    protected HttpRequestHandler wrapSocket(Socket socket) {
        return new HttpRequestHandler(socket);
    }

}

And adapt Server like so:

public abstract class Server<T extends RequestHandler> {

    protected abstract T wrapSocket(Socket socket);

    protected void handleNewConnectionRequest(Socket socket) {
        try {
            executorService.submit(wrapSocket(socket));
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

}

Just a thought…