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/*
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* Copyright (c) 1999, 2006, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package java.lang.reflect;
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/**
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* {@code InvocationHandler} is the interface implemented by
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* the <i>invocation handler</i> of a proxy instance.
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*
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* <p>Each proxy instance has an associated invocation handler.
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* When a method is invoked on a proxy instance, the method
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* invocation is encoded and dispatched to the {@code invoke}
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* method of its invocation handler.
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*
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* @author Peter Jones
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* @see Proxy
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* @since 1.3
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*/
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public interface InvocationHandler {
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/**
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* Processes a method invocation on a proxy instance and returns
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* the result. This method will be invoked on an invocation handler
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* when a method is invoked on a proxy instance that it is
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* associated with.
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*
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* @param proxy the proxy instance that the method was invoked on
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*
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* @param method the {@code Method} instance corresponding to
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* the interface method invoked on the proxy instance. The declaring
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* class of the {@code Method} object will be the interface that
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* the method was declared in, which may be a superinterface of the
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* proxy interface that the proxy class inherits the method through.
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*
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* @param args an array of objects containing the values of the
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* arguments passed in the method invocation on the proxy instance,
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* or {@code null} if interface method takes no arguments.
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* Arguments of primitive types are wrapped in instances of the
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* appropriate primitive wrapper class, such as
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* {@code java.lang.Integer} or {@code java.lang.Boolean}.
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*
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* @return the value to return from the method invocation on the
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* proxy instance. If the declared return type of the interface
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* method is a primitive type, then the value returned by
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* this method must be an instance of the corresponding primitive
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* wrapper class; otherwise, it must be a type assignable to the
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* declared return type. If the value returned by this method is
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* {@code null} and the interface method's return type is
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* primitive, then a {@code NullPointerException} will be
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* thrown by the method invocation on the proxy instance. If the
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* value returned by this method is otherwise not compatible with
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* the interface method's declared return type as described above,
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* a {@code ClassCastException} will be thrown by the method
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* invocation on the proxy instance.
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*
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* @throws Throwable the exception to throw from the method
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* invocation on the proxy instance. The exception's type must be
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* assignable either to any of the exception types declared in the
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* {@code throws} clause of the interface method or to the
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* unchecked exception types {@code java.lang.RuntimeException}
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* or {@code java.lang.Error}. If a checked exception is
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* thrown by this method that is not assignable to any of the
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* exception types declared in the {@code throws} clause of
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* the interface method, then an
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* {@link UndeclaredThrowableException} containing the
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* exception that was thrown by this method will be thrown by the
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* method invocation on the proxy instance.
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*
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* @see UndeclaredThrowableException
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*/
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public Object invoke(Object proxy, Method method, Object[] args)
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throws Throwable;
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}
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