| 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 | } |