1 | /* |
2 | * Copyright 2005-2006 Sun Microsystems, Inc. All Rights Reserved. |
3 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
4 | * |
5 | * This code is free software; you can redistribute it and/or modify it |
6 | * under the terms of the GNU General Public License version 2 only, as |
7 | * published by the Free Software Foundation. Sun designates this |
8 | * particular file as subject to the "Classpath" exception as provided |
9 | * by Sun in the LICENSE file that accompanied this code. |
10 | * |
11 | * This code is distributed in the hope that it will be useful, but WITHOUT |
12 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
13 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
14 | * version 2 for more details (a copy is included in the LICENSE file that |
15 | * accompanied this code). |
16 | * |
17 | * You should have received a copy of the GNU General Public License version |
18 | * 2 along with this work; if not, write to the Free Software Foundation, |
19 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
20 | * |
21 | * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
22 | * CA 95054 USA or visit www.sun.com if you need additional information or |
23 | * have any questions. |
24 | */ |
25 | |
26 | package javax.lang.model.util; |
27 | |
28 | import javax.lang.model.element.*; |
29 | import javax.annotation.processing.SupportedSourceVersion; |
30 | import static javax.lang.model.element.ElementKind.*; |
31 | import javax.lang.model.SourceVersion; |
32 | import static javax.lang.model.SourceVersion.*; |
33 | |
34 | |
35 | /** |
36 | * A scanning visitor of program elements with default behavior |
37 | * appropriate for the {@link SourceVersion#RELEASE_6 RELEASE_6} |
38 | * source version. The <tt>visit<i>XYZ</i></tt> methods in this |
39 | * class scan their component elements by calling {@code scan} on |
40 | * their {@linkplain Element#getEnclosedElements enclosed elements}, |
41 | * {@linkplain ExecutableElement#getParameters parameters}, etc., as |
42 | * indicated in the individual method specifications. A subclass can |
43 | * control the order elements are visited by overriding the |
44 | * <tt>visit<i>XYZ</i></tt> methods. Note that clients of a scanner |
45 | * may get the desired behavior be invoking {@code v.scan(e, p)} rather |
46 | * than {@code v.visit(e, p)} on the root objects of interest. |
47 | * |
48 | * <p>When a subclass overrides a <tt>visit<i>XYZ</i></tt> method, the |
49 | * new method can cause the enclosed elements to be scanned in the |
50 | * default way by calling <tt>super.visit<i>XYZ</i></tt>. In this |
51 | * fashion, the concrete visitor can control the ordering of traversal |
52 | * over the component elements with respect to the additional |
53 | * processing; for example, consistently calling |
54 | * <tt>super.visit<i>XYZ</i></tt> at the start of the overridden |
55 | * methods will yield a preorder traversal, etc. If the component |
56 | * elements should be traversed in some other order, instead of |
57 | * calling <tt>super.visit<i>XYZ</i></tt>, an overriding visit method |
58 | * should call {@code scan} with the elements in the desired order. |
59 | * |
60 | * <p> Methods in this class may be overridden subject to their |
61 | * general contract. Note that annotating methods in concrete |
62 | * subclasses with {@link java.lang.Override @Override} will help |
63 | * ensure that methods are overridden as intended. |
64 | * |
65 | * <p> <b>WARNING:</b> The {@code ElementVisitor} interface |
66 | * implemented by this class may have methods added to it in the |
67 | * future to accommodate new, currently unknown, language structures |
68 | * added to future versions of the Java™ programming language. |
69 | * Therefore, methods whose names begin with {@code "visit"} may be |
70 | * added to this class in the future; to avoid incompatibilities, |
71 | * classes which extend this class should not declare any instance |
72 | * methods with names beginning with {@code "visit"}. |
73 | * |
74 | * <p>When such a new visit method is added, the default |
75 | * implementation in this class will be to call the {@link |
76 | * #visitUnknown visitUnknown} method. A new element scanner visitor |
77 | * class will also be introduced to correspond to the new language |
78 | * level; this visitor will have different default behavior for the |
79 | * visit method in question. When the new visitor is introduced, all |
80 | * or portions of this visitor may be deprecated. |
81 | * |
82 | * @param <R> the return type of this visitor's methods. Use {@link |
83 | * Void} for visitors that do not need to return results. |
84 | * @param <P> the type of the additional parameter to this visitor's |
85 | * methods. Use {@code Void} for visitors that do not need an |
86 | * additional parameter. |
87 | * |
88 | * @author Joseph D. Darcy |
89 | * @author Scott Seligman |
90 | * @author Peter von der Ahé |
91 | * @since 1.6 |
92 | */ |
93 | @SupportedSourceVersion(RELEASE_6) |
94 | public class ElementScanner6<R, P> extends AbstractElementVisitor6<R, P> { |
95 | /** |
96 | * The specified default value. |
97 | */ |
98 | protected final R DEFAULT_VALUE; |
99 | |
100 | /** |
101 | * Constructor for concrete subclasses; uses {@code null} for the |
102 | * default value. |
103 | */ |
104 | protected ElementScanner6(){ |
105 | DEFAULT_VALUE = null; |
106 | } |
107 | |
108 | /** |
109 | * Constructor for concrete subclasses; uses the argument for the |
110 | * default value. |
111 | */ |
112 | protected ElementScanner6(R defaultValue){ |
113 | DEFAULT_VALUE = defaultValue; |
114 | } |
115 | |
116 | /** |
117 | * Iterates over the given elements and calls {@link |
118 | * #scan(Element, Object) scan(Element, P)} on each one. Returns |
119 | * the result of the last call to {@code scan} or {@code |
120 | * DEFAULT_VALUE} for an empty iterable. |
121 | * |
122 | * @param iterable the elements to scan |
123 | * @param p additional parameter |
124 | * @return the scan of the last element or {@code DEFAULT_VALUE} if no elements |
125 | */ |
126 | public final R scan(Iterable<? extends Element> iterable, P p) { |
127 | R result = DEFAULT_VALUE; |
128 | for(Element e : iterable) |
129 | result = scan(e, p); |
130 | return result; |
131 | } |
132 | |
133 | /** |
134 | * Processes an element by calling {@code e.accept(this, p)}; |
135 | * this method may be overridden by subclasses. |
136 | * @return the result of visiting {@code e}. |
137 | */ |
138 | public R scan(Element e, P p) { |
139 | return e.accept(this, p); |
140 | } |
141 | |
142 | /** |
143 | * Convenience method equivalent to {@code v.scan(e, null)}. |
144 | * @return the result of scanning {@code e}. |
145 | */ |
146 | public final R scan(Element e) { |
147 | return scan(e, null); |
148 | } |
149 | |
150 | /** |
151 | * {@inheritDoc} This implementation scans the enclosed elements. |
152 | * |
153 | * @param e the element to visit |
154 | * @param p a visitor-specified parameter |
155 | * @return the result of scanning |
156 | */ |
157 | public R visitPackage(PackageElement e, P p) { |
158 | return scan(e.getEnclosedElements(), p); |
159 | } |
160 | |
161 | /** |
162 | * {@inheritDoc} This implementation scans the enclosed elements. |
163 | * |
164 | * @param e the element to visit |
165 | * @param p a visitor-specified parameter |
166 | * @return the result of scanning |
167 | */ |
168 | public R visitType(TypeElement e, P p) { |
169 | return scan(e.getEnclosedElements(), p); |
170 | } |
171 | |
172 | /** |
173 | * {@inheritDoc} This implementation scans the enclosed elements. |
174 | * |
175 | * @param e the element to visit |
176 | * @param p a visitor-specified parameter |
177 | * @return the result of scanning |
178 | */ |
179 | public R visitVariable(VariableElement e, P p) { |
180 | return scan(e.getEnclosedElements(), p); |
181 | } |
182 | |
183 | /** |
184 | * {@inheritDoc} This implementation scans the parameters. |
185 | * |
186 | * @param e the element to visit |
187 | * @param p a visitor-specified parameter |
188 | * @return the result of scanning |
189 | */ |
190 | public R visitExecutable(ExecutableElement e, P p) { |
191 | return scan(e.getParameters(), p); |
192 | } |
193 | |
194 | /** |
195 | * {@inheritDoc} This implementation scans the enclosed elements. |
196 | * |
197 | * @param e the element to visit |
198 | * @param p a visitor-specified parameter |
199 | * @return the result of scanning |
200 | */ |
201 | public R visitTypeParameter(TypeParameterElement e, P p) { |
202 | return scan(e.getEnclosedElements(), p); |
203 | } |
204 | } |