package org.apidesign.gc;

 import java.awt.Color;

 import java.beans.PropertyChangeEvent;

 import java.beans.PropertyChangeListener;

 import java.lang.ref.WeakReference;

 import javax.swing.JPanel;

 import org.junit.After;

 import org.junit.AfterClass;

 import org.junit.Before;

 import org.junit.BeforeClass;

 import org.junit.Test;

 import org.netbeans.junit.NbTestCase;

 import static org.junit.Assert.*;

 public class WeakListenersTest {

     private static JPanel longLivingBean;

     public WeakListenersTest() {

     }

     @BeforeClass

     public static void setUpClass() throws Exception {

         longLivingBean = new JPanel();

     }

     @Before

     public void setUp() {

         longLivingBean.setBackground(Color.BLACK);

     }

     @Test

     public void listenWithoutWeakReference() {

         PropL listener = new PropL();

         longLivingBean.addPropertyChangeListener(listener);

         longLivingBean.setBackground(Color.WHITE);

         assertEquals("background property change notified", "background", listener.propName);

         WeakReference<Object> ref = new WeakReference<Object>(listener);

         listener = null;

         try {

             NbTestCase.assertGC(

                 "Of course, this listener cannot disappear, because it is held from long living JavaBean", 

                 ref

             );

         } catch (Exception ex) {

             ex.printStackTrace();

             // of course it cannot

             return;

         }

         fail("The listener cannot be GCed as it is held from long living JavaBean");

     }

     @Test

     public void listenViaWeakListener() {

         PropL listener = new PropL();

         PropertyChangeListener weakL = WeakListeners.create(PropertyChangeListener.class, listener, longLivingBean);

         longLivingBean.addPropertyChangeListener(weakL);

         longLivingBean.setBackground(Color.WHITE);

         assertEquals("background property change notified", "background", listener.propName);

         // BEGIN: gc.assertGC

         WeakReference<Object> ref = new WeakReference<Object>(listener);

         listener = null;

         NbTestCase.assertGC("This listener can disappear", ref);

         // END: gc.assertGC

     }

     private static class PropL implements PropertyChangeListener {

         String propName;

         public void propertyChange(PropertyChangeEvent evt) {

             propName = evt.getPropertyName();

         }

     }

 }