PropertyEvaluator


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19  
20  package org.netbeans.modules.ruby.spi.project.support.rake;
21  
22  import java.beans.PropertyChangeListener  ;
23  import java.util.Map  ;
24  
25  /**
26   * A way of mapping property names to values.
27   * <p>
28   * This interface defines no independent thread safety, but in typical usage
29   * it will be used with the project manager mutex. Changes should be fired
30   * synchronously.
31   * @author Jesse Glick
32   * @see PropertyUtils#sequentialPropertyEvaluator
33   * @see RakeProjectHelper#getStandardPropertyEvaluator
34   */
35  public interface PropertyEvaluator {
36  
37      /**
38       * Evaluate a single property.
39       * @param prop the name of a property
40       * @return its value, or null if it is not defined or its value could not be
41       *         retrieved for some reason (e.g. a circular definition)
42       */
43      String   getProperty(String   prop);
44      
45      /**
46       * Evaluate a block of text possibly containing property references.
47       * The syntax is the same as for Ant: <samp>${foo}</samp> means the value
48       * of the property <samp>foo</samp>; <samp>$$</samp> is an escape for
49       * <samp>$</samp>; references to undefined properties are left unsubstituted.
50       * @param text some text possibly containing one or more property references
51       * @return its value, or null if some problem (such a circular definition) made
52       *         it impossible to retrieve the values of some properties
53       */
54      String   evaluate(String   text);
55      
56      /**
57       * Get a set of all current property definitions at once.
58       * This may be more efficient than evaluating individual properties,
59       * depending on the implementation.
60       * @return an immutable map from property names to values, or null if the
61       *         mapping could not be computed (e.g. due to a circular definition)
62       */
63      Map  <String  ,String  > getProperties();
64      
65      /**
66       * Add a listener to changes in particular property values.
67       * As generally true with property change listeners, the old and new
68       * values may both be null in case the true values are not known or not
69       * easily computed; and the property name might be null to signal that any
70       * property might have changed.
71       * @param listener a listener to add
72       */
73      void addPropertyChangeListener(PropertyChangeListener   listener);
74      
75      /**
76       * Remove a listener to changes in particular property values.
77       * @param listener a listener to remove
78       */
79      void removePropertyChangeListener(PropertyChangeListener   listener);
80      
81  }
82
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