001 // Copyright 2004, 2005 The Apache Software Foundation
002 //
003 // Licensed under the Apache License, Version 2.0 (the "License");
004 // you may not use this file except in compliance with the License.
005 // You may obtain a copy of the License at
006 //
007 // http://www.apache.org/licenses/LICENSE-2.0
008 //
009 // Unless required by applicable law or agreed to in writing, software
010 // distributed under the License is distributed on an "AS IS" BASIS,
011 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
012 // See the License for the specific language governing permissions and
013 // limitations under the License.
014
015 package org.apache.hivemind.service;
016
017 import java.lang.reflect.Method;
018
019 /**
020 * A representation of a {@link java.lang.reflect.Method}, identifying the name, return type,
021 * parameter types and exception types. Actual Method objects are tied to a particular class, and
022 * don't compare well with other otherwise identical Methods from other classes or interface;
023 * MethodSignatures are distinct from classes and compare well.
024 * <p>
025 * Because the intended purpose is to compare methods from interfaces (which are always public and
026 * abstract) we don't bother to actually track the modifiers. In addition, at this time,
027 * MethodSignature <em>does not distinguish between instance and static
028 * methods</em>.
029 *
030 * @author Howard Lewis Ship
031 */
032 public class MethodSignature
033 {
034 private int _hashCode = -1;
035
036 private Class _returnType;
037
038 private String _name;
039
040 private Class[] _parameterTypes;
041
042 private Class[] _exceptionTypes;
043
044 public MethodSignature(Class returnType, String name, Class[] parameterTypes,
045 Class[] exceptionTypes)
046 {
047 _returnType = returnType;
048 _name = name;
049 _parameterTypes = parameterTypes;
050 _exceptionTypes = exceptionTypes;
051 }
052
053 public MethodSignature(Method m)
054 {
055 this(m.getReturnType(), m.getName(), m.getParameterTypes(), m.getExceptionTypes());
056 }
057
058 /**
059 * Returns the exceptions for this method. Caution: do not modify the returned array. May return
060 * null.
061 */
062 public Class[] getExceptionTypes()
063 {
064 return _exceptionTypes;
065 }
066
067 public String getName()
068 {
069 return _name;
070 }
071
072 /**
073 * Returns the parameter types for this method. May return null. Caution: do not modify the
074 * returned array.
075 */
076 public Class[] getParameterTypes()
077 {
078 return _parameterTypes;
079 }
080
081 public Class getReturnType()
082 {
083 return _returnType;
084 }
085
086 public int hashCode()
087 {
088 if (_hashCode == -1)
089 {
090
091 _hashCode = _returnType.hashCode();
092
093 _hashCode = 31 * _hashCode + _name.hashCode();
094
095 int count = count(_parameterTypes);
096
097 for (int i = 0; i < count; i++)
098 _hashCode = 31 * _hashCode + _parameterTypes[i].hashCode();
099
100 count = count(_exceptionTypes);
101
102 for (int i = 0; i < count; i++)
103 _hashCode = 31 * _hashCode + _exceptionTypes[i].hashCode();
104 }
105
106 return _hashCode;
107 }
108
109 private static int count(Object[] array)
110 {
111 return array == null ? 0 : array.length;
112 }
113
114 /**
115 * Returns true if the other object is an instance of MethodSignature with identical values for
116 * return type, name, parameter types and exception types.
117 */
118 public boolean equals(Object o)
119 {
120 if (o == null || !(o instanceof MethodSignature))
121 return false;
122
123 MethodSignature ms = (MethodSignature) o;
124
125 if (_returnType != ms._returnType)
126 return false;
127
128 if (!_name.equals(ms._name))
129 return false;
130
131 if (mismatch(_parameterTypes, ms._parameterTypes))
132 return false;
133
134 return !mismatch(_exceptionTypes, ms._exceptionTypes);
135 }
136
137 private boolean mismatch(Class[] a1, Class[] a2)
138 {
139 int a1Count = count(a1);
140 int a2Count = count(a2);
141
142 if (a1Count != a2Count)
143 return true;
144
145 // Hm. What if order is important (for exceptions)? We're really saying here that they
146 // were derived from the name Method.
147
148 for (int i = 0; i < a1Count; i++)
149 {
150 if (a1[i] != a2[i])
151 return true;
152 }
153
154 return false;
155 }
156
157 public String toString()
158 {
159 StringBuffer buffer = new StringBuffer();
160
161 buffer.append(ClassFabUtils.getJavaClassName(_returnType));
162 buffer.append(" ");
163 buffer.append(_name);
164 buffer.append("(");
165
166 for (int i = 0; i < count(_parameterTypes); i++)
167 {
168 if (i > 0)
169 buffer.append(", ");
170
171 buffer.append(ClassFabUtils.getJavaClassName(_parameterTypes[i]));
172 }
173
174 buffer.append(")");
175
176 for (int i = 0; i < count(_exceptionTypes); i++)
177 {
178 if (i == 0)
179 buffer.append(" throws ");
180 else
181 buffer.append(", ");
182
183 buffer.append(_exceptionTypes[i].getName());
184 }
185
186 return buffer.toString();
187 }
188
189 /**
190 * Returns a string consisting of the name of the method and its parameter values. This is
191 * similar to {@link #toString()}, but omits the return type and information about thrown
192 * exceptions. A unique id is used by {@link MethodIterator} to identify overlapping methods
193 * (methods with the same name but different thrown exceptions).
194 *
195 * @since 1.1
196 */
197 public String getUniqueId()
198 {
199 StringBuffer buffer = new StringBuffer(_name);
200 buffer.append("(");
201
202 for (int i = 0; i < count(_parameterTypes); i++)
203 {
204 if (i > 0)
205 buffer.append(",");
206
207 buffer.append(ClassFabUtils.getJavaClassName(_parameterTypes[i]));
208 }
209
210 buffer.append(")");
211
212 return buffer.toString();
213 }
214
215 /**
216 * Returns true if this signature has the same return type, name and parameters types as the
217 * method signature passed in, and this signatures exceptions "trump" (are the same as, or
218 * super-implementations of, all exceptions thrown by the other method signature).
219 *
220 * @since 1.1
221 */
222
223 public boolean isOverridingSignatureOf(MethodSignature ms)
224 {
225 if (_returnType != ms._returnType)
226 return false;
227
228 if (!_name.equals(ms._name))
229 return false;
230
231 if (mismatch(_parameterTypes, ms._parameterTypes))
232 return false;
233
234 return exceptionsEncompass(ms._exceptionTypes);
235 }
236
237 /**
238 * The nuts and bolts of checking that another method signature's exceptions are a subset of
239 * this signature's.
240 *
241 * @since 1.1
242 */
243
244 private boolean exceptionsEncompass(Class[] otherExceptions)
245 {
246 int ourCount = count(_exceptionTypes);
247 int otherCount = count(otherExceptions);
248
249 // If we have no exceptions, then ours encompass theirs only if they
250 // have no exceptions, either.
251
252 if (ourCount == 0)
253 return otherCount == 0;
254
255 boolean[] matched = new boolean[otherCount];
256 int unmatched = otherCount;
257
258 for (int i = 0; i < ourCount && unmatched > 0; i++)
259 {
260 for (int j = 0; j < otherCount; j++)
261 {
262 // Ignore exceptions that have already been matched
263
264 if (matched[j])
265 continue;
266
267 // When one of our exceptions is a super-class of one of their exceptions,
268 // then their exceptions is matched.
269
270 if (_exceptionTypes[i].isAssignableFrom(otherExceptions[j]))
271 {
272 matched[j] = true;
273 unmatched--;
274 }
275 }
276 }
277
278 return unmatched == 0;
279 }
280 }