1 /*
2 * Copyright (c) 2005, 2008, 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 javax.management.openmbean;
27
28 import com.sun.jmx.mbeanserver.MXBeanLookup;
29 import com.sun.jmx.mbeanserver.MXBeanMapping;
30 import com.sun.jmx.mbeanserver.MXBeanMappingFactory;
31 import com.sun.jmx.mbeanserver.DefaultMXBeanMappingFactory;
32 import java.lang.reflect.InvocationHandler;
33 import java.lang.reflect.Method;
34 import java.lang.reflect.Proxy;
35
36 /**
37 <p>An {@link InvocationHandler} that forwards getter methods to a
38 {@link CompositeData}. If you have an interface that contains
39 only getter methods (such as {@code String getName()} or
40 {@code boolean isActive()}) then you can use this class in
41 conjunction with the {@link Proxy} class to produce an implementation
42 of the interface where each getter returns the value of the
43 corresponding item in a {@code CompositeData}.</p>
44
45 <p>For example, suppose you have an interface like this:
46
47 <blockquote>
48 <pre>
49 public interface NamedNumber {
50 public int getNumber();
51 public String getName();
52 }
53 </pre>
54 </blockquote>
55
56 and a {@code CompositeData} constructed like this:
57
58 <blockquote>
59 <pre>
60 CompositeData cd =
61 new {@link CompositeDataSupport}(
62 someCompositeType,
63 new String[] {"number", "name"},
64 new Object[] {<b>5</b>, "five"}
65 );
66 </pre>
67 </blockquote>
68
69 then you can construct an object implementing {@code NamedNumber}
70 and backed by the object {@code cd} like this:
71
72 <blockquote>
73 <pre>
74 InvocationHandler handler =
75 new CompositeDataInvocationHandler(cd);
76 NamedNumber nn = (NamedNumber)
77 Proxy.newProxyInstance(NamedNumber.class.getClassLoader(),
78 new Class[] {NamedNumber.class},
79 handler);
80 </pre>
81 </blockquote>
82
83 A call to {@code nn.getNumber()} will then return <b>5</b>.</p>
84
85 <p>If the first letter of the property defined by a getter is a
86 capital, then this handler will look first for an item in the
87 {@code CompositeData} beginning with a capital, then, if that is
88 not found, for an item beginning with the corresponding lowercase
89 letter or code point. For a getter called {@code getNumber()}, the
90 handler will first look for an item called {@code Number}, then for
91 {@code number}. If the getter is called {@code getnumber()}, then
92 the item must be called {@code number}.</p>
93
94 <p>If the method given to {@link #invoke invoke} is the method
95 {@code boolean equals(Object)} inherited from {@code Object}, then
96 it will return true if and only if the argument is a {@code Proxy}
97 whose {@code InvocationHandler} is also a {@code
98 CompositeDataInvocationHandler} and whose backing {@code
99 CompositeData} is equal (not necessarily identical) to this
100 object's. If the method given to {@code invoke} is the method
101 {@code int hashCode()} inherited from {@code Object}, then it will
102 return a value that is consistent with this definition of {@code
103 equals}: if two objects are equal according to {@code equals}, then
104 they will have the same {@code hashCode}.</p>
105
106 @since 1.6
107 */
108 public class CompositeDataInvocationHandler implements InvocationHandler {
109 /**
110 <p>Construct a handler backed by the given {@code
111 CompositeData}.</p>
112
113 @param compositeData the {@code CompositeData} that will supply
114 information to getters.
115
116 @throws IllegalArgumentException if {@code compositeData}
117 is null.
118 */
119 public CompositeDataInvocationHandler(CompositeData compositeData) {
120 this(compositeData, null);
121 }
122
123 /**
124 <p>Construct a handler backed by the given {@code
125 CompositeData}.</p>
126
127 @param compositeData the {@code CompositeData} that will supply
128 information to getters.
129
130 @throws IllegalArgumentException if {@code compositeData}
131 is null.
132 */
133 CompositeDataInvocationHandler(CompositeData compositeData,
134 MXBeanLookup lookup) {
135 if (compositeData == null)
136 throw new IllegalArgumentException("compositeData");
137 this.compositeData = compositeData;
138 this.lookup = lookup;
139 }
140
141 /**
142 Return the {@code CompositeData} that was supplied to the
143 constructor.
144 @return the {@code CompositeData} that this handler is backed
145 by. This is never null.
146 */
147 public CompositeData getCompositeData() {
148 assert compositeData != null;
149 return compositeData;
150 }
151
152 public Object invoke(Object proxy, Method method, Object[] args)
153 throws Throwable {
154 final String methodName = method.getName();
155
156 // Handle the methods from java.lang.Object
157 if (method.getDeclaringClass() == Object.class) {
158 if (methodName.equals("toString") && args == null)
159 return "Proxy[" + compositeData + "]";
160 else if (methodName.equals("hashCode") && args == null)
161 return compositeData.hashCode() + 0x43444948;
162 else if (methodName.equals("equals") && args.length == 1
163 && method.getParameterTypes()[0] == Object.class)
164 return equals(proxy, args[0]);
165 else {
166 /* Either someone is calling invoke by hand, or
167 it is a non-final method from Object overriden
168 by the generated Proxy. At the time of writing,
169 the only non-final methods in Object that are not
170 handled above are finalize and clone, and these
171 are not overridden in generated proxies. */
172 return method.invoke(this, args);
173 }
174 }
175
176 String propertyName = DefaultMXBeanMappingFactory.propertyName(method);
177 if (propertyName == null) {
178 throw new IllegalArgumentException("Method is not getter: " +
179 method.getName());
180 }
181 Object openValue;
182 if (compositeData.containsKey(propertyName))
183 openValue = compositeData.get(propertyName);
184 else {
185 String decap = DefaultMXBeanMappingFactory.decapitalize(propertyName);
186 if (compositeData.containsKey(decap))
187 openValue = compositeData.get(decap);
188 else {
189 final String msg =
190 "No CompositeData item " + propertyName +
191 (decap.equals(propertyName) ? "" : " or " + decap) +
192 " to match " + methodName;
193 throw new IllegalArgumentException(msg);
194 }
195 }
196 MXBeanMapping mapping =
197 MXBeanMappingFactory.DEFAULT.mappingForType(method.getGenericReturnType(),
198 MXBeanMappingFactory.DEFAULT);
199 return mapping.fromOpenValue(openValue);
200 }
201
202 /* This method is called when equals(Object) is
203 * called on our proxy and hence forwarded to us. For example, if we
204 * are a proxy for an interface like this:
205 * public interface GetString {
206 * public String string();
207 * }
208 * then we must compare equal to another CompositeDataInvocationHandler
209 * proxy for the same interface and where string() returns the same value.
210 *
211 * You might think that we should also compare equal to another
212 * object that implements GetString directly rather than using
213 * Proxy, provided that its string() returns the same result as
214 * ours, and in fact an earlier version of this class did that (by
215 * converting the other object into a CompositeData and comparing
216 * that with ours). But in fact that doesn't make a great deal of
217 * sense because there's absolutely no guarantee that the
218 * resulting equals would be reflexive (otherObject.equals(this)
219 * might be false even if this.equals(otherObject) is true), and,
220 * especially, there's no way we could generate a hashCode() that
221 * would be equal to otherObject.hashCode() when
222 * this.equals(otherObject), because we don't know how
223 * otherObject.hashCode() is computed.
224 */
225 private boolean equals(Object proxy, Object other) {
226 if (other == null)
227 return false;
228
229 final Class<?> proxyClass = proxy.getClass();
230 final Class<?> otherClass = other.getClass();
231 if (proxyClass != otherClass)
232 return false;
233 InvocationHandler otherih = Proxy.getInvocationHandler(other);
234 if (!(otherih instanceof CompositeDataInvocationHandler))
235 return false;
236 CompositeDataInvocationHandler othercdih =
237 (CompositeDataInvocationHandler) otherih;
238 return compositeData.equals(othercdih.compositeData);
239 }
240
241 private final CompositeData compositeData;
242 private final MXBeanLookup lookup;
243 }