ResettableContext


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16   * Software is Sun Microsystems, Inc. Portions Copyright 1997-2006 Sun
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19  
20  package org.netbeans.spi.registry;
21  
22  import org.netbeans.api.registry.ContextException;
23  
24  /**
25   * {@link BasicContext} extension supporting default values. If the implementation of
26   * backend storage has concept of default values it should implement also
27   * this context extension which allows examination of whether the
28   * bound object has some default value, whether current value is modified
29   * or the original one and also allows to revert the modified value to the
30   * default one.
31   *
32   * <p>If the binding name is <code>null</code> then the context is examined. The context
33   * should be considered as modified if following condition is true for it or
34   * for any of its subcontexts: some binding in the context is modified or list
35   * of subcontext is different from default one. Reverting context means that
36   * all modified bindings in the context (including the subcontexts) are reverted
37   * and all nondefault subcontexts are destroyed.
38   *
39   * @author  David Konecny
40   */
41  public interface ResettableContext extends BasicContext {
42  
43      /**
44       * Exist a default value?
45       *
46       * @param bindingName the binding name or null for the context
47       * @return true if there is a default
48       */    
49      boolean hasDefault(String   bindingName);
50  
51      /**
52       * Check whether the value is modified.
53       * For existing binding for which there is no default value
54       * (that is {@link #hasDefault} is false) returns this method
55       * always true.
56       *
57       * @param bindingName the binding name or null for the context
58       * @return true if default value is modified; always returns true if 
59       *         default value does not exist
60       */    
61      boolean isModified(String   bindingName);
62  
63      /**
64       * Revert modification. Will do something only if value is modified
65       * (ie. {@link #isModified} returns true). If there is no default
66       * value (ie. {@link #hasDefault} returns false) the revert operation
67       * is identical to unbinding of object or destroying of context
68       * content.
69       *
70       * @param bindingName the binding name or null for the context
71       * @throws ContextException can throw exception if there were problems
72       *         during removal of modified values
73       */    
74      void revert(String   bindingName) throws ContextException;
75  
76  }
77
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