01: /*
02: * @(#)InvocationHandler.java 1.12 06/10/10
03: *
04: * Copyright 1990-2006 Sun Microsystems, Inc. All Rights Reserved.
05: * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER
06: *
07: * This program is free software; you can redistribute it and/or
08: * modify it under the terms of the GNU General Public License version
09: * 2 only, as published by the Free Software Foundation.
10: *
11: * This program is distributed in the hope that it will be useful, but
12: * WITHOUT ANY WARRANTY; without even the implied warranty of
13: * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14: * General Public License version 2 for more details (a copy is
15: * included at /legal/license.txt).
16: *
17: * You should have received a copy of the GNU General Public License
18: * version 2 along with this work; if not, write to the Free Software
19: * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
20: * 02110-1301 USA
21: *
22: * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa
23: * Clara, CA 95054 or visit www.sun.com if you need additional
24: * information or have any questions.
25: *
26: */
27:
28: package java.lang.reflect;
29:
30: /**
31: * <code>InvocationHandler</code> is the interface implemented by
32: * the <i>invocation handler</i> of a proxy instance.
33: *
34: * <p>Each proxy instance has an associated invocation handler.
35: * When a method is invoked on a proxy instance, the method
36: * invocation is encoded and dispatched to the <code>invoke</code>
37: * method of its invocation handler.
38: *
39: * @author Peter Jones
40: * @version 1.5, 00/02/02
41: * @see Proxy
42: * @since JDK1.3
43: */
44: public interface InvocationHandler {
45:
46: /**
47: * Processes a method invocation on a proxy instance and returns
48: * the result. This method will be invoked on an invocation handler
49: * when a method is invoked on a proxy instance that it is
50: * associated with.
51: *
52: * @param proxy the proxy instance that the method was invoked on
53: *
54: * @param method the <code>Method</code> instance corresponding to
55: * the interface method invoked on the proxy instance. The declaring
56: * class of the <code>Method</code> object will be the interface that
57: * the method was declared in, which may be a superinterface of the
58: * proxy interface that the proxy class inherits the method through.
59: *
60: * @param args an array of objects containing the values of the
61: * arguments passed in the method invocation on the proxy instance,
62: * or <code>null</code> if interface method takes no arguments.
63: * Arguments of primitive types are wrapped in instances of the
64: * appropriate primitive wrapper class, such as
65: * <code>java.lang.Integer</code> or <code>java.lang.Boolean</code>.
66: *
67: * @return the value to return from the method invocation on the
68: * proxy instance. If the declared return type of the interface
69: * method is a primitive type, then the value returned by
70: * this method must be an instance of the corresponding primitive
71: * wrapper class; otherwise, it must be a type assignable to the
72: * declared return type. If the value returned by this method is
73: * <code>null</code> and the interface method's return type is
74: * primitive, then a <code>NullPointerException</code> will be
75: * thrown by the method invocation on the proxy instance. If the
76: * value returned by this method is otherwise not compatible with
77: * the interface method's declared return type as described above,
78: * a <code>ClassCastException</code> will be thrown by the method
79: * invocation on the proxy instance.
80: *
81: * @throws Throwable the exception to throw from the method
82: * invocation on the proxy instance. The exception's type must be
83: * assignable either to any of the exception types declared in the
84: * <code>throws</code> clause of the interface method or to the
85: * unchecked exception types <code>java.lang.RuntimeException</code>
86: * or <code>java.lang.Error</code>. If a checked exception is
87: * thrown by this method that is not assignable to any of the
88: * exception types declared in the <code>throws</code> clause of
89: * the interface method, then an
90: * {@link UndeclaredThrowableException} containing the
91: * exception that was thrown by this method will be thrown by the
92: * method invocation on the proxy instance.
93: *
94: * @see UndeclaredThrowableException
95: */
96: public Object invoke(Object proxy, Method method, Object[] args)
97: throws Throwable;
98: }
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