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 * Copyright (c) 1999, 2006, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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package java.lang.reflect;

/**

 * {@code InvocationHandler} is the interface implemented by

 * the <i>invocation handler</i> of a proxy instance.

 *

 * <p>Each proxy instance has an associated invocation handler.

 * When a method is invoked on a proxy instance, the method

 * invocation is encoded and dispatched to the {@code invoke}

 * method of its invocation handler.

 *

 * @author      Peter Jones

 * @see         Proxy

 * @since       1.3

 */

public interface InvocationHandler {

    /**

     * Processes a method invocation on a proxy instance and returns

     * the result.  This method will be invoked on an invocation handler

     * when a method is invoked on a proxy instance that it is

     * associated with.

     *

     * @param   proxy the proxy instance that the method was invoked on

     *

     * @param   method the {@code Method} instance corresponding to

     * the interface method invoked on the proxy instance.  The declaring

     * class of the {@code Method} object will be the interface that

     * the method was declared in, which may be a superinterface of the

     * proxy interface that the proxy class inherits the method through.

     *

     * @param   args an array of objects containing the values of the

     * arguments passed in the method invocation on the proxy instance,

     * or {@code null} if interface method takes no arguments.

     * Arguments of primitive types are wrapped in instances of the

     * appropriate primitive wrapper class, such as

     * {@code java.lang.Integer} or {@code java.lang.Boolean}.

     *

     * @return  the value to return from the method invocation on the

     * proxy instance.  If the declared return type of the interface

     * method is a primitive type, then the value returned by

     * this method must be an instance of the corresponding primitive

     * wrapper class; otherwise, it must be a type assignable to the

     * declared return type.  If the value returned by this method is

     * {@code null} and the interface method's return type is

     * primitive, then a {@code NullPointerException} will be

     * thrown by the method invocation on the proxy instance.  If the

     * value returned by this method is otherwise not compatible with

     * the interface method's declared return type as described above,

     * a {@code ClassCastException} will be thrown by the method

     * invocation on the proxy instance.

     *

     * @throws  Throwable the exception to throw from the method

     * invocation on the proxy instance.  The exception's type must be

     * assignable either to any of the exception types declared in the

     * {@code throws} clause of the interface method or to the

     * unchecked exception types {@code java.lang.RuntimeException}

     * or {@code java.lang.Error}.  If a checked exception is

     * thrown by this method that is not assignable to any of the

     * exception types declared in the {@code throws} clause of

     * the interface method, then an

     * {@link UndeclaredThrowableException} containing the

     * exception that was thrown by this method will be thrown by the

     * method invocation on the proxy instance.

     *

     * @see     UndeclaredThrowableException

     */

    public Object invoke(Object proxy, Method method, Object[] args)

        throws Throwable;

}