FilterPropertyProvider


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12   * enclosed by brackets [] replaced by your own identifying information:
13   * "Portions Copyrighted [year] [name of copyright owner]"
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15   * The Original Software is NetBeans. The Initial Developer of the Original
16   * Software is Sun Microsystems, Inc. Portions Copyright 1997-2006 Sun
17   * Microsystems, Inc. All Rights Reserved.
18   */
19  
20  package org.netbeans.spi.project.support.ant;
21  
22  import java.util.ArrayList  ;
23  import java.util.List  ;
24  import java.util.Map  ;
25  import javax.swing.event.ChangeEvent  ;
26  import javax.swing.event.ChangeListener  ;
27  import org.openide.util.WeakListeners;
28  
29  /**
30   * Property provider that delegates to another source.
31   * Useful, for example, when conditionally loading from one or another properties file.
32   * @since org.netbeans.modules.project.ant/1 1.14
33   */
34  public abstract class FilterPropertyProvider implements PropertyProvider {
35  
36      private PropertyProvider delegate;
37      private final List  <ChangeListener  > listeners = new ArrayList  <ChangeListener  >();
38      private final ChangeListener   strongListener = new ChangeListener  () {
39          public void stateChanged(ChangeEvent   e) {
40              //System.err.println("DPP: change from current provider " + delegate);
41              fireChange();
42          }
43      };
44      private ChangeListener   weakListener = null; // #50572: must be weak
45  
46      /**
47       * Initialize the proxy.
48       * @param delegate the initial delegate to use
49       */
50      protected FilterPropertyProvider(PropertyProvider delegate) {
51          assert delegate != null;
52          setDelegate(delegate);
53      }
54  
55      /**
56       * Change the current delegate (firing changes as well).
57       * @param delegate the initial delegate to use
58       */
59      protected final void setDelegate(PropertyProvider delegate) {
60          if (delegate == this.delegate) {
61              return;
62          }
63          if (this.delegate != null) {
64              assert weakListener != null;
65              this.delegate.removeChangeListener(weakListener);
66          }
67          this.delegate = delegate;
68          weakListener = WeakListeners.change(strongListener, delegate);
69          delegate.addChangeListener(weakListener);
70          fireChange();
71      }
72  
73      public final Map  <String  , String  > getProperties() {
74          return delegate.getProperties();
75      }
76  
77      public final synchronized void addChangeListener(ChangeListener   listener) {
78          // XXX could listen to delegate only when this has listeners
79          listeners.add(listener);
80      }
81  
82      public final synchronized void removeChangeListener(ChangeListener   listener) {
83          listeners.add(listener);
84      }
85  
86      private void fireChange() {
87          ChangeListener  [] ls;
88          synchronized (this) {
89              if (listeners.isEmpty()) {
90                  return;
91              }
92              ls = listeners.toArray(new ChangeListener  [listeners.size()]);
93          }
94          ChangeEvent   ev = new ChangeEvent  (this);
95          for(ChangeListener   l : ls) {
96              l.stateChanged(ev);
97          }
98      }
99  
100 }
101
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