CS 580 Assignment 2.1 Client-Server Programming Code Analysis - Prof. R. E. Whitney, Assignments of Computer Science

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CS 580 Client-Server Programming

Spring Semester, 2007

Comments on Assignment 2.

Feb 20, 2007

Hard Coded Server

public void sendMessage(String message) { String host = "bismarck.sdsu.edu"; int port = 8009;

Is this better

private String send(String text) { try { // creates a stream socket and connects it to the server Socket connection = new Socket(strServer, iPort); //getOutputStream will return an output stream for this socket OutputStream rawOut = connection.getOutputStream(); //OutputStream is super class to BufferedOutputStream. PrintStream creates a new // print stream. //BufferedOutputStream creates a new buffered output stream to write data to the // specified output stream PrintStream out = new PrintStream(new BufferedOutputStream(rawOut)); //getInputStream returns an inputstream for this socket InputStream rawIn = connection.getInputStream(); //BufferedReader creates a buffering character-input stream tht uses a default input // buffer //InputStreamReader creates an InputStreamReader that uses the default-size input // buffer BufferedReader in = new BufferedReader(new InputStreamReader(rawIn)); out.print(text); //flush() will flush the stream out.flush();

What do we lose without the Comments?

private String send(String text) { try { Socket connection = new Socket(strServer, iPort); OutputStream rawOut = connection.getOutputStream(); PrintStream out = new PrintStream(new BufferedOutputStream(rawOut)); InputStream rawIn = connection.getInputStream(); BufferedReader in = new BufferedReader(new InputStreamReader(rawIn)); out.print(text); out.flush();

Does this need comments?

public class Client { public Client(String serverAddress, int portNumber) { Improved names reduce the need for the given comments

How about this comment?

public class Client { /*

• @param serverAddress as DNS name ie "rohan.sdsu.edu" */ public Client(String serverAddress, int serverPort) {

Mixing UI with Domain Code

public class Client { public String add() { System.out.print("Type name to add to server"); String name = Console.readLine(); Socket connection = new Socket(strServer, iPort); OutputStream rawOut = connection.getOutputStream(); PrintStream out = new PrintStream(new BufferedOutputStream(rawOut)); InputStream rawIn = connection.getInputStream(); BufferedReader in = new BufferedReader(new InputStreamReader(rawIn)); out.print("add " + name + ';'); out.flush(); etc. Just Say No

Mixing UI with Domain Code

UI & Domain Code Perform different tasks Change at different rates No need to tie doman code to particular UI Put UI code in separate layer Keep Domain code ignorant of UI code

The Text UI Menu System

pubic class ClientTUI { private Client voter; private static ENDLINE = System.getProperty("line.separator"); string mainMenu() { return "Select one of the following options:" + ENDLINE + "1) add" + ENDLINE + "2) list" + ENDLINE + "3) vote" + ENDLINE + "4) result" + ENDLINE + "5) quit"; } void add() { name = Console.readLine ("Enter a name to add"); String result = voter.add( name); Console.println(" The result: " + result); } public void run() { while (true) { int method = Console.readInt( mainMenu()); switch (method) { case: 1: add(); break; case: 2: list(); break; etc.

Why Is Text UI done from Scratch Each Time?

Build some structure that can be reused

readLine()

Avoid readline (what is a line?) Does not work with protocol on server

Whtswthllthabrnsthyrhrdtrd

Flag Names

private String serverResponse(Reader fromServer) { StringBuffer response = new StringBuffer(); boolean hasMoreChars = true; int next = 0; while (hasMoreChars) { next = fromServer.read(); if (-1 == next) hasMoreChars = false; else if(';' ==(char) next) hasMoreChars = false; else response.append((char) currentChar); } return response.toString(); } What role does the flag play

Do we need the flag?

private String serverResponse(Reader fromServer) { StringBuffer response = new StringBuffer(); int next = 0; while (true) { next = fromServer.read(); if (isEOF(next)) return response.toString(); else if (isEndOfMessage(next)) return response.toString(); else response.append((char) next); } }