java/11 : java.base/java/lang/reflect/InvocationHandler.java

InvocationHandler
- invoke(Object, Method, Object[]): Object

https://openjdk.java.net/

GPLv2 + Classpath Exception

/*
 * 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
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package java.lang.reflect;

InvocationHandler is the interface implemented by the invocation handler of a proxy instance.
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 invoke method of its invocation handler. 
Author:      Peter Jones
See Also: Proxy
Since:       1.3/**
 * {@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.
Params: proxy – the proxy instance that the method was invoked on
method – the Method instance corresponding to the interface method invoked on the proxy instance. The declaring class of the 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.
args – an array of objects containing the values of the arguments passed in the method invocation on the proxy instance, or null if interface method takes no arguments. Arguments of primitive types are wrapped in instances of the appropriate primitive wrapper class, such as java.lang.Integer or java.lang.Boolean.
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 throws clause of the interface method or to the unchecked exception types java.lang.RuntimeException or 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 throws clause of the interface method, then an UndeclaredThrowableException containing the exception that was thrown by this method will be thrown by the method invocation on the proxy instance.
See Also: UndeclaredThrowableException
Returns:  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 null and the interface method's return type is primitive, then a 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 ClassCastException will be thrown by the method invocation on the proxy instance./**
     * 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;
}

Params:	proxy – the proxy instance that the method was invoked on method – the `Method` instance corresponding to the interface method invoked on the proxy instance. The declaring class of the `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. args – an array of objects containing the values of the arguments passed in the method invocation on the proxy instance, or `null` if interface method takes no arguments. Arguments of primitive types are wrapped in instances of the appropriate primitive wrapper class, such as `java.lang.Integer` or `java.lang.Boolean`.
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 `throws` clause of the interface method or to the unchecked exception types `java.lang.RuntimeException` or `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 `throws` clause of the interface method, then an `UndeclaredThrowableException` containing the exception that was thrown by this method will be thrown by the method invocation on the proxy instance.
See Also:	UndeclaredThrowableException
Returns:	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 `null` and the interface method's return type is primitive, then a `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 `ClassCastException` will be thrown by the method invocation on the proxy instance.

/

java/ 11/ java.base/java/lang/reflect/InvocationHandler.java