Android Open Source - CipherChat User Database

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License

The source code is released under:

MIT License

Java Source Code

package com.desperate;
/* w  w w .  j  a  v  a  2 s .co  m*/
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.net.InetAddress;
import java.util.HashMap;
import java.util.LinkedList;

/**
 * A thread-safe database that saves information of registered users.
 * <p>
 * The users are accessed through their user names, which are unique. It's possible to get a list of all the users that are online at the moment. The
 * whole database can be serialized to a file using the method {@link #save()}.
 * 
 * @author SIRS group 10 - First Semester 2013
 * 
 */
public class UserDatabase implements Serializable {

  private static final long serialVersionUID = 1L;

  private static final String databaseFileName = "users.udb";

  /**
   * Stores user data. Key is the user's username.
   */
  private HashMap<String, User> users;

  public UserDatabase() {

    this.users = new HashMap<String, User>();
  }

  /**
   * Adds a new user to the database. If a user with the same name already exists, this function fails and returns false.
   * 
   * @param user
   *            user to be added
   * @return true if the user was added. false otherwise
   */
  public synchronized boolean addUser(User user) {

    if (users.containsKey(user.userName)) {
      return false;
    } else {
      users.put(user.userName, user);
      return true;
    }
  }

  /**
   * Gets the username data, given a username.
   * 
   * @param userName
   *            Name the user used to register
   * @return data of the user
   * @throws Exception
   */
  public synchronized User getUser(String userName) throws Exception {

    User user = users.get(userName);

    if (user == null) {
      throw new Exception("User does not exists.");
    }

    return user;

  }

  public static synchronized void save(UserDatabase database) {

    try {
      FileOutputStream fileOut = new FileOutputStream(databaseFileName);
      ObjectOutputStream out = new ObjectOutputStream(fileOut);
      out.writeObject(database);
      out.close();
      fileOut.close();
      System.out.println("Serialized data is saved in " + databaseFileName);
    } catch (IOException e) {
      e.printStackTrace();
    }
  }

  /**
   * Loads a database from disk. File name is {@value #databaseFileName}.
   * 
   * @return database loaded from file
   */
  public static UserDatabase load() {

    UserDatabase database = new UserDatabase();

    try {
      FileInputStream fileIn = new FileInputStream(databaseFileName);
      ObjectInputStream in = new ObjectInputStream(fileIn);

      database = (UserDatabase) in.readObject();

      in.close();
      fileIn.close();
      System.out.println("Serialized data is loaded from " + databaseFileName);

    } catch (IOException e) {
      System.err.println("No database found. New database created");
      e.printStackTrace();
    } catch (ClassNotFoundException e) {
      System.err.println("Database was created with an older version of server. New database created.");
      e.printStackTrace();
    }

    return database;
  }

  /**
   * Gets the IP address of a user.
   * 
   * @param userName
   * @return
   */
  public synchronized InetAddress getIP(String userName) {

    User user = users.get(userName);

    if (user != null)
      return users.get(userName).ip;
    else
      return null;
  }

  /**
   * Prints info of all the users to standard output.
   */
  public synchronized void printUserList() {

    System.out.printf("%-10s\t%s\n", "      Name", "    Address", " State");

    for (User u : users.values()) {
      System.out.printf("%-16s    %9s    %18s\n", u.userName, u.ip, u.getOnlineStatus() ? "online" : "offline");
    }
  }

  public synchronized void save() {

    UserDatabase.save(this);
  }

  /**
   * Gets an array of Strings containing the names of all online users, except the requesting client itself.
   * 
   * @param requester
   *            User that issued the list request.
   * @return usernames of all currenly online users, except the <b>requester</b>
   */
  public synchronized String[] getOnlineUserList(User requester) {

    LinkedList<String> onlineUsers = new LinkedList<String>();

    for (User u : users.values()) {
      if (u.getOnlineStatus() == true && !u.equals(requester)) {
        onlineUsers.add(u.userName);
      }
    }

    String[] onlineUserNames = new String[onlineUsers.size()];

    for (int i = 0; i < onlineUserNames.length; i++) {
      onlineUserNames[i] = onlineUsers.get(i);
      System.out.println("Online user: " + onlineUserNames[i]);
    }

    return onlineUserNames;
  }
}

Java Source Code List

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