KOProject/ClientSessionThread.java

package com.collibra.server;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import java.net.SocketTimeoutException;
import java.util.UUID;

/**
 * Every time a new client connects to the server a new thread is created for the client's session.
 * The session stays active until the client times out or the client sends a disconnect message.
 * @version 1.0
 * @author Yordan Kirov
 * @since 21/11/2018
 */
class ClientSessionThread extends Thread {

    /** Socket used for communication between the server and the client.  */
    private final Socket clientSocket;

    /** The time when the client has connected.  */
    private long startTime;

    /** The name of the client that is retrieved after the initial communication.  */
    private String clientName = null;

    /**
     * Indicator whether the client session is still active or not.
     * When it is made inactive the client gets disconnected.
     */
    private boolean isSessionActive;

    /**  Universally unique identifier of the client session.    */
    private final String sessionId;

    /**
     * Constructor
     * Initializes the start time of the connection.
     * Sets the session to active.
     * Generates a universally unique identifier of the client session.
     * @param clientSocket the socket on which the client connects to the server.
     */
    public ClientSessionThread(Socket clientSocket) {
        System.out.println("Client connected.");
        this.clientSocket = clientSocket;
        this.startTime = System.currentTimeMillis();
        this.isSessionActive = true;
        this.sessionId = UUID.randomUUID().toString();
    }

    /**
     * Initializes the communication between the server and the client.
     * Sends a first message to the client.
     * Sets the client name if the client sends it properly or waits to receive it.
     * Takes all commands of the client and answers to them.
     * When an error occurs the connection with the client is closed.
     */
    public void run() {
        PrintWriter out = null;
        BufferedReader in = null;
        try {
            out = new PrintWriter(clientSocket.getOutputStream(), true);
            in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));

            SimpleProtocol.sendFirstMessage(out, sessionId);

            String inputLine;
            while (isSessionActive && (inputLine = in.readLine()) != null) {
                if (this.clientName == null) {
                    this.clientName = SimpleProtocol.retrieveClientName(out, inputLine);
                } else {
                    acceptMessage(inputLine, out);
                }
            }
        } catch (SocketTimeoutException se) {
            System.out.println(this.clientName + " TIMED OUT!!!");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            SimpleProtocol.sendGoodbyeMessage(out, this.clientName, startTime);

            disconnect();
        }
    }

    /**
     * Accepts client messages and executes the commands according to the SimpleProtocol.
     * @param clientMessage message coming from the client
     * @param out the PrintWriter with which the server sends messages to the client.
     */
    private void acceptMessage(String clientMessage, PrintWriter out) {
        if ("BYE MATE!".equals(clientMessage)) {
            this.isSessionActive = false;
            return;
        }

        String serverMessage;
        if (clientMessage.startsWith("ADD NODE ")) {
            serverMessage = SimpleProtocol.addNode(clientMessage);
        } else if (clientMessage.startsWith("ADD EDGE ")) {
            serverMessage = SimpleProtocol.addEdge(clientMessage);
        } else if (clientMessage.startsWith("REMOVE NODE ")) {
            serverMessage = SimpleProtocol.removeNode(clientMessage);
        } else if (clientMessage.startsWith("REMOVE EDGE ")) {
            serverMessage = SimpleProtocol.removeEdge(clientMessage);
        } else if (clientMessage.startsWith("SHORTEST PATH ")) {
            serverMessage = SimpleProtocol.getShortestPath(clientMessage);
        } else if (clientMessage.startsWith("CLOSER THAN ")) {
            serverMessage = SimpleProtocol.getCloserThan(clientMessage);
        } else {
            serverMessage = SimpleProtocol.unsupportedCommand();
        }

        debugToConsole(clientMessage, serverMessage);

        out.println(serverMessage);
    }

    private void debugToConsole(String clientMessage, String serverMessage) {
        if (Server.DEBUG) {
            System.out.println(">>>" + clientMessage);
            System.out.println(serverMessage);
        }
    }

    private void disconnect() {
        System.out.println("Closing the connection: " + this.clientName);

        try {
            if (clientSocket != null) {
                clientSocket.close();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}