Processing ObjectPool Class

2015-08-11 [EverydaySketch]

by schrodingers

HTML

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<canvas></canvas>

CSS

</style> <script type="text/javascript"> window.addEventListener('load', function() {
    var scripts=document.body.getElementsByTagName('script');
    var canvases=document.body.getElementsByTagName('canvas');
    new Processing(canvases[0], scripts[0].text);
}
, false);
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JavaScript

/* 
 title: ObjectPool Class
 date: 2015-08-11
 */
color[] spring = {
      #ff6699, #ff9900, #ffcc00, #9adb1b, #00cc66, #00cccc, #00ccff, #6633cc, #ff66cc
      };
color violet = color(58, 48, 66);
color yellow = color(237, 230, 35);
color cyan = color(5, 190, 255);

      
void setup() {
    size(800, 600);
    smooth(5);
}
      
 void draw() {    
      background(222);
      
}

// ObjectPool Class

public abstract class ObjectPool<T> {
  private long expirationTime;

  private Hashtable<T, Long> locked, unlocked;

  public ObjectPool() {
    expirationTime = 30000; // 30 seconds
    locked = new Hashtable<T, Long>();
    unlocked = new Hashtable<T, Long>();
  }

  protected abstract T create();

  public abstract boolean validate(T o);

  public abstract void expire(T o);

  public synchronized T checkOut() {
    long now = System.currentTimeMillis();
    T t;
    if (unlocked.size() > 0) {
      Enumeration<T> e = unlocked.keys();
      while (e.hasMoreElements()) {
        t = e.nextElement();
        if ((now - unlocked.get(t)) > expirationTime) {
          // object has expired
          unlocked.remove(t);
          expire(t);
          t = null;
        } else {
          if (validate(t)) {
            unlocked.remove(t);
            locked.put(t, now);
            return (t);
          } else {
            // object failed validation
            unlocked.remove(t);
            expire(t);
            t = null;
          }
        }
      }
    }
    // no objects available, create a new one
    t = create();
    locked.put(t, now);
    return (t);
  }

  public synchronized void checkIn(T t) {
    locked.remove(t);
    unlocked.put(t, System.currentTimeMillis());
  }
}

//The three remaining methods are abstract 
//and therefore must be implemented by the subclass

public class JDBCConnectionPool extends ObjectPool<Connection> {

  private String dsn, usr, pwd;

  public JDBCConnectionPool(String driver, String dsn, String usr, String pwd) {
   ...