01 /*
02 * Copyright 1999-2006 Sun Microsystems, Inc. All Rights Reserved.
03 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
04 *
05 * This code is free software; you can redistribute it and/or modify it
06 * under the terms of the GNU General Public License version 2 only, as
07 * published by the Free Software Foundation. Sun designates this
08 * particular file as subject to the "Classpath" exception as provided
09 * 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 java.lang.reflect;
27
28 /**
29 * {@code InvocationHandler} is the interface implemented by
30 * the <i>invocation handler</i> of a proxy instance.
31 *
32 * <p>Each proxy instance has an associated invocation handler.
33 * When a method is invoked on a proxy instance, the method
34 * invocation is encoded and dispatched to the {@code invoke}
35 * method of its invocation handler.
36 *
37 * @author Peter Jones
38 * @version 1.18, 07/06/22
39 * @see Proxy
40 * @since 1.3
41 */
42 public interface InvocationHandler {
43
44 /**
45 * Processes a method invocation on a proxy instance and returns
46 * the result. This method will be invoked on an invocation handler
47 * when a method is invoked on a proxy instance that it is
48 * associated with.
49 *
50 * @param proxy the proxy instance that the method was invoked on
51 *
52 * @param method the {@code Method} instance corresponding to
53 * the interface method invoked on the proxy instance. The declaring
54 * class of the {@code Method} object will be the interface that
55 * the method was declared in, which may be a superinterface of the
56 * proxy interface that the proxy class inherits the method through.
57 *
58 * @param args an array of objects containing the values of the
59 * arguments passed in the method invocation on the proxy instance,
60 * or {@code null} if interface method takes no arguments.
61 * Arguments of primitive types are wrapped in instances of the
62 * appropriate primitive wrapper class, such as
63 * {@code java.lang.Integer} or {@code java.lang.Boolean}.
64 *
65 * @return the value to return from the method invocation on the
66 * proxy instance. If the declared return type of the interface
67 * method is a primitive type, then the value returned by
68 * this method must be an instance of the corresponding primitive
69 * wrapper class; otherwise, it must be a type assignable to the
70 * declared return type. If the value returned by this method is
71 * {@code null} and the interface method's return type is
72 * primitive, then a {@code NullPointerException} will be
73 * thrown by the method invocation on the proxy instance. If the
74 * value returned by this method is otherwise not compatible with
75 * the interface method's declared return type as described above,
76 * a {@code ClassCastException} will be thrown by the method
77 * invocation on the proxy instance.
78 *
79 * @throws Throwable the exception to throw from the method
80 * invocation on the proxy instance. The exception's type must be
81 * assignable either to any of the exception types declared in the
82 * {@code throws} clause of the interface method or to the
83 * unchecked exception types {@code java.lang.RuntimeException}
84 * or {@code java.lang.Error}. If a checked exception is
85 * thrown by this method that is not assignable to any of the
86 * exception types declared in the {@code throws} clause of
87 * the interface method, then an
88 * {@link UndeclaredThrowableException} containing the
89 * exception that was thrown by this method will be thrown by the
90 * method invocation on the proxy instance.
91 *
92 * @see UndeclaredThrowableException
93 */
94 public Object invoke(Object proxy, Method method, Object[] args)
95 throws Throwable;
96 }
|