Property Manager : Properties « Development Class « Java

Property Manager

//package abc.util;

import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.util.ArrayList;
import java.util.Hashtable;
import java.util.Properties;

public final class PropertyManager {

  private final static String DEFAULT_PROPERTIES_FILE = "ressources" + File.separator + "";
  private final static String APP_PROPERTIES_FILE = "ressources" + File.separator + "";

  private Properties defaultProps = new Properties();
  private Properties appProps = null;

  private Hashtable listeners = null;

  private static Object lock = new Object();
  private static PropertyManager instance  = null;

  private PropertyManager() {

  public static PropertyManager getInstance() throws IOException {
  if (instance == null) {
    synchronized (lock) {
      if (instance == null) {
        instance = new PropertyManager();
  return (instance);


  private void loadProperties()  throws IOException {

    // create and load default properties
    FileInputStream in = new FileInputStream(DEFAULT_PROPERTIES_FILE);

    // create application properties with default
    appProps = new Properties(defaultProps);

    try {
    // user/application properties
      in = new FileInputStream(APP_PROPERTIES_FILE);
    } catch (Throwable th) {
    // TODO: log something


  public void storeProperties() throws IOException {

    FileOutputStream out = new FileOutputStream(DEFAULT_PROPERTIES_FILE);, "---Default properties---");

    out = new FileOutputStream(APP_PROPERTIES_FILE);, "---App/User properties---");


  public String getProperty(String key) {
  String val = null;
  if (key != null) {
    if (appProps != null)
      val = (String)appProps.getProperty(key);
    if (val == null) {
      val = defaultProps.getProperty(key);
  return (val);


   * Sets Application/User String properties; default property values cannot be set.
  public void setProperty(String key, String val) {

  ArrayList list  = null;
  Object oldValue = null;

  oldValue = getProperty(key);

  appProps.setProperty(key, val);
  if (listeners.containsKey(key)) {
    list = (ArrayList)listeners.get(key);
    int len = list.size();
    if (len > 0) {
    PropertyChangeEvent evt = new PropertyChangeEvent(this, key, oldValue, val);
    for (int i=0; i < len; i++) {
      if (list.get(i) instanceof PropertyChangeListener)


  public boolean addListener (String key, PropertyChangeListener listener) {
  boolean added = false;
  ArrayList list = null;
  if (listeners == null)
    listeners = new Hashtable();

  if (!listeners.contains(key)) {
    list = new ArrayList();
    added = list.add(listener);
    listeners.put(key, list);
    } else {
    list = (ArrayList)listeners.get(key);
    added = list.add(listener);
  return (added);

  public void removeListener (PropertyChangeListener listener) {
  if (listeners != null && listeners.size() > 0)


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