1 /*
2 * Copyright (c) 1996, 2018, Oracle and/or its affiliates. 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. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package java.beans;
27
28 import java.lang.ref.Reference;
29 import java.lang.ref.WeakReference;
30 import java.lang.reflect.Method;
31 import java.util.List;
32 import java.util.ArrayList;
33
34 /**
35 * A MethodDescriptor describes a particular method that a Java Bean
36 * supports for external access from other components.
37 *
38 * @since 1.1
39 */
40
41 public class MethodDescriptor extends FeatureDescriptor {
42
43 private final MethodRef methodRef = new MethodRef();
44
45 private String[] paramNames;
46
47 private List<WeakReference<Class<?>>> params;
48
49 private ParameterDescriptor[] parameterDescriptors;
50
51 /**
52 * Constructs a {@code MethodDescriptor} from a
53 * {@code Method}.
54 *
55 * @param method The low-level method information.
56 */
57 public MethodDescriptor(Method method) {
58 this(method, null);
59 }
60
61
62 /**
63 * Constructs a {@code MethodDescriptor} from a
64 * {@code Method} providing descriptive information for each
65 * of the method's parameters.
66 *
67 * @param method The low-level method information.
68 * @param parameterDescriptors Descriptive information for each of the
69 * method's parameters.
70 */
71 public MethodDescriptor(Method method,
72 ParameterDescriptor[] parameterDescriptors) {
73 setName(method.getName());
74 setMethod(method);
75 this.parameterDescriptors = (parameterDescriptors != null)
76 ? parameterDescriptors.clone()
77 : null;
78 }
79
80 /**
81 * Gets the method that this MethodDescriptor encapsulates.
82 *
83 * @return The low-level description of the method
84 */
85 public synchronized Method getMethod() {
86 Method method = this.methodRef.get();
87 if (method == null) {
88 Class<?> cls = getClass0();
89 String name = getName();
90 if ((cls != null) && (name != null)) {
91 Class<?>[] params = getParams();
92 if (params == null) {
93 for (int i = 0; i < 3; i++) {
94 // Find methods for up to 2 params. We are guessing here.
95 // This block should never execute unless the classloader
96 // that loaded the argument classes disappears.
97 method = Introspector.findMethod(cls, name, i, null);
98 if (method != null) {
99 break;
100 }
101 }
102 } else {
103 method = Introspector.findMethod(cls, name, params.length, params);
104 }
105 setMethod(method);
106 }
107 }
108 return method;
109 }
110
111 private synchronized void setMethod(Method method) {
112 if (method == null) {
113 return;
114 }
115 if (getClass0() == null) {
116 setClass0(method.getDeclaringClass());
117 }
118 setParams(getParameterTypes(getClass0(), method));
119 this.methodRef.set(method);
120 }
121
122 private synchronized void setParams(Class<?>[] param) {
123 if (param == null) {
124 return;
125 }
126 paramNames = new String[param.length];
127 params = new ArrayList<>(param.length);
128 for (int i = 0; i < param.length; i++) {
129 paramNames[i] = param[i].getName();
130 params.add(new WeakReference<Class<?>>(param[i]));
131 }
132 }
133
134 // pp getParamNames used as an optimization to avoid method.getParameterTypes.
135 String[] getParamNames() {
136 return paramNames;
137 }
138
139 private synchronized Class<?>[] getParams() {
140 Class<?>[] clss = new Class<?>[params.size()];
141
142 for (int i = 0; i < params.size(); i++) {
143 Reference<? extends Class<?>> ref = (Reference<? extends Class<?>>)params.get(i);
144 Class<?> cls = ref.get();
145 if (cls == null) {
146 return null;
147 } else {
148 clss[i] = cls;
149 }
150 }
151 return clss;
152 }
153
154 /**
155 * Gets the ParameterDescriptor for each of this MethodDescriptor's
156 * method's parameters.
157 *
158 * @return The locale-independent names of the parameters. May return
159 * a null array if the parameter names aren't known.
160 */
161 public ParameterDescriptor[] getParameterDescriptors() {
162 return (this.parameterDescriptors != null)
163 ? this.parameterDescriptors.clone()
164 : null;
165 }
166
167 private static Method resolve(Method oldMethod, Method newMethod) {
168 if (oldMethod == null) {
169 return newMethod;
170 }
171 if (newMethod == null) {
172 return oldMethod;
173 }
174 return !oldMethod.isSynthetic() && newMethod.isSynthetic() ? oldMethod : newMethod;
175 }
176
177 /*
178 * Package-private constructor
179 * Merge two method descriptors. Where they conflict, give the
180 * second argument (y) priority over the first argument (x).
181 * @param x The first (lower priority) MethodDescriptor
182 * @param y The second (higher priority) MethodDescriptor
183 */
184
185 MethodDescriptor(MethodDescriptor x, MethodDescriptor y) {
186 super(x, y);
187
188 this.methodRef.set(resolve(x.methodRef.get(), y.methodRef.get()));
189 params = x.params;
190 if (y.params != null) {
191 params = y.params;
192 }
193 paramNames = x.paramNames;
194 if (y.paramNames != null) {
195 paramNames = y.paramNames;
196 }
197
198 parameterDescriptors = x.parameterDescriptors;
199 if (y.parameterDescriptors != null) {
200 parameterDescriptors = y.parameterDescriptors;
201 }
202 }
203
204 /*
205 * Package-private dup constructor
206 * This must isolate the new object from any changes to the old object.
207 */
208 MethodDescriptor(MethodDescriptor old) {
209 super(old);
210
211 this.methodRef.set(old.getMethod());
212 params = old.params;
213 paramNames = old.paramNames;
214
215 if (old.parameterDescriptors != null) {
216 int len = old.parameterDescriptors.length;
217 parameterDescriptors = new ParameterDescriptor[len];
218 for (int i = 0; i < len ; i++) {
219 parameterDescriptors[i] = new ParameterDescriptor(old.parameterDescriptors[i]);
220 }
221 }
222 }
223
224 void appendTo(StringBuilder sb) {
225 appendTo(sb, "method", this.methodRef.get());
226 if (this.parameterDescriptors != null) {
227 sb.append("; parameterDescriptors={");
228 for (ParameterDescriptor pd : this.parameterDescriptors) {
229 sb.append(pd).append(", ");
230 }
231 sb.setLength(sb.length() - 2);
232 sb.append("}");
233 }
234 }
235 }