NodeEventHandler


1   /*******************************************************************************
2    * Copyright (c) 2004 IBM Corporation and others.
3    * All rights reserved. This program and the accompanying materials
4    * are made available under the terms of the Eclipse Public License v1.0
5    * which accompanies this distribution, and is available at
6    * http://www.eclipse.org/legal/epl-v10.html
7    *
8    * Contributors:
9    *     IBM Corporation - initial API and implementation
10   *******************************************************************************/
11  package org.eclipse.jdt.core.dom;
12  
13  /**
14   * A node event handler is an internal mechanism for receiving
15   * notification of changes to nodes in an AST.
16   * <p>
17   * The default implementation serves as the default event handler
18   * that does nothing. Internal subclasses do all the real work.
19   * </p>
20   * 
21   * @see AST#getEventHandler()
22   */
23  class NodeEventHandler {
24  
25      /**
26       * Creates a node event handler.
27       */
28      NodeEventHandler() {
29          // default implementation: do nothing
30      }
31      
32      /**
33       * Reports that the given node is about to lose a child.
34       * The first half of an event pair. The default implementation does nothing.
35       * 
36       * @param node the node about to be modified
37       * @param child the node about to be removed
38       * @param property the child or child list property descriptor
39       * @see #postRemoveChildEvent(ASTNode, ASTNode, StructuralPropertyDescriptor)
40       * @since 3.0
41       */
42      void preRemoveChildEvent(ASTNode node, ASTNode child, StructuralPropertyDescriptor property) {
43          // do nothing
44          // System.out.println("DEL1 " + property); //$NON-NLS-1$
45      }
46      
47      /**
48       * Reports that the given node has just lose a child.
49       * The second half of an event pair. The default implementation does nothing.
50       * 
51       * @param node the node that was modified
52       * @param child the child that was removed; note that this node is unparented
53       * @param property the child or child list property descriptor
54       * @see #preRemoveChildEvent(ASTNode, ASTNode, StructuralPropertyDescriptor)
55       * @since 3.0
56       */
57      void postRemoveChildEvent(ASTNode node, ASTNode child, StructuralPropertyDescriptor property) {
58          // do nothing
59          // System.out.println("DEL2 " + property); //$NON-NLS-1$
60      }
61      
62      /**
63       * Reports that the given node is about to have a child replaced.
64       * The first half of an event pair.
65       * The default implementation does nothing.
66       * 
67       * @param node the node about to be modified
68       * @param child the node about to be replaced
69       * @param newChild the replacement child; note that this node is unparented
70       * @param property the child or child list property descriptor
71       * @see #preReplaceChildEvent(ASTNode, ASTNode, ASTNode, StructuralPropertyDescriptor)
72       * @since 3.0
73       */
74      void preReplaceChildEvent(ASTNode node, ASTNode child, ASTNode newChild, StructuralPropertyDescriptor property) {
75          // do nothing
76          // System.out.println("REP1 " + property); //$NON-NLS-1$
77      }
78      
79      /**
80       * Reports that the given node has had its child replaced. The second half
81       * of an event pair. The default implementation does nothing.
82       * 
83       * @param node the node that was modified
84       * @param child the node that was replaced; note that this node is unparented
85       * @param newChild the replacement child
86       * @param property the child or child list property descriptor
87       * @see #postReplaceChildEvent(ASTNode, ASTNode, ASTNode, StructuralPropertyDescriptor)
88       * @since 3.0
89       */
90      void postReplaceChildEvent(ASTNode node, ASTNode child, ASTNode newChild, StructuralPropertyDescriptor property) {
91          // do nothing
92          // System.out.println("REP2 " + property); //$NON-NLS-1$
93      }
94      
95      /**
96       * Reports that the given node is about to gain a child.
97       * The first half of an event pair. The default implementation does nothing.
98       * 
99       * @param node the node that to be modified
100      * @param child the node that is to be added as a child; note that this
101      * node is unparented; in the case of a child list property, the exact
102      * location of insertion is not supplied (but is known on the
103      * corresponding <code>postAddChildEvent</code> to
104      * follow)
105      * @param property the child or child list property descriptor
106      * @see #postAddChildEvent(ASTNode, ASTNode, StructuralPropertyDescriptor)
107      * @since 3.0
108      */
109     void preAddChildEvent(ASTNode node, ASTNode child, StructuralPropertyDescriptor property) {
110         // do nothing
111         // System.out.println("ADD1 " + property); //$NON-NLS-1$
112     }
113     
114     /**
115      * Reports that the given node has just gained a child.
116      * The second half of an event pair. The default implementation does nothing.
117      * 
118      * @param node the node that was modified
119      * @param child the node that was added as a child
120      * @param property the child or child list property descriptor
121      * @see #preAddChildEvent(ASTNode, ASTNode, StructuralPropertyDescriptor)
122      * @since 3.0
123      */
124     void postAddChildEvent(ASTNode node, ASTNode child, StructuralPropertyDescriptor property) {
125         // do nothing
126         // System.out.println("ADD2 " + property); //$NON-NLS-1$
127     }
128     
129     /**
130      * Reports that the given node is about to change the value of a
131      * non-child property. The first half of an event pair.
132      * The default implementation does nothing.
133      * 
134      * @param node the node to be modified
135      * @param property the property descriptor
136      * @see #postValueChangeEvent(ASTNode, SimplePropertyDescriptor)
137      * @since 3.0
138      */
139     void preValueChangeEvent(ASTNode node, SimplePropertyDescriptor property) {
140         // do nothing
141         // System.out.println("MOD1 " + property); //$NON-NLS-1$
142     }
143 
144     /**
145      * Reports that the given node has just changed the value of a
146      * non-child property. The second half of an event pair.
147      * The default implementation does nothing.
148      * 
149      * @param node the node that was modified
150      * @param property the property descriptor
151      * @see #preValueChangeEvent(ASTNode, SimplePropertyDescriptor)
152      * @since 3.0
153      */
154     void postValueChangeEvent(ASTNode node, SimplePropertyDescriptor property) {
155         // do nothing
156         // System.out.println("MOD2 " + property); //$NON-NLS-1$
157     }
158     
159     /**
160      * Reports that the given node is about to be cloned. 
161      * The first half of an event pair.
162      * The default implementation does nothing.
163      * 
164      * @param node the node to be modified
165      * @see #postCloneNodeEvent(ASTNode, ASTNode)
166      * @since 3.0
167      */
168     void preCloneNodeEvent(ASTNode node) {
169         // do nothing
170         // System.out.println("CLONE1"); //$NON-NLS-1$
171     }
172 
173     /**
174      * Reports that the given node has just been cloned.
175      * The second half of an event pair.
176      * The default implementation does nothing.
177      * 
178      * @param node the node that was modified
179      * @param clone the clone of <code>node</code>
180      * @see #preCloneNodeEvent(ASTNode)
181      * @since 3.0
182      */
183     void postCloneNodeEvent(ASTNode node, ASTNode clone) {
184         // do nothing
185         // System.out.println("CLONE2"); //$NON-NLS-1$
186     }
187     
188 }
189
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