jaroslav@601: /*
jaroslav@601:  * Copyright (c) 1999, 2010, Oracle and/or its affiliates. All rights reserved.
jaroslav@601:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
jaroslav@601:  *
jaroslav@601:  * This code is free software; you can redistribute it and/or modify it
jaroslav@601:  * under the terms of the GNU General Public License version 2 only, as
jaroslav@601:  * published by the Free Software Foundation.  Oracle designates this
jaroslav@601:  * particular file as subject to the "Classpath" exception as provided
jaroslav@601:  * by Oracle in the LICENSE file that accompanied this code.
jaroslav@601:  *
jaroslav@601:  * This code is distributed in the hope that it will be useful, but WITHOUT
jaroslav@601:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
jaroslav@601:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
jaroslav@601:  * version 2 for more details (a copy is included in the LICENSE file that
jaroslav@601:  * accompanied this code).
jaroslav@601:  *
jaroslav@601:  * You should have received a copy of the GNU General Public License version
jaroslav@601:  * 2 along with this work; if not, write to the Free Software Foundation,
jaroslav@601:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
jaroslav@601:  *
jaroslav@601:  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
jaroslav@601:  * or visit www.oracle.com if you need additional information or have any
jaroslav@601:  * questions.
jaroslav@601:  */
jaroslav@601: 
jaroslav@601: package java.lang.reflect;
jaroslav@601: 
jaroslav@601: 
jaroslav@601: /**
jaroslav@601:  * {@code Proxy} provides static methods for creating dynamic proxy
jaroslav@601:  * classes and instances, and it is also the superclass of all
jaroslav@601:  * dynamic proxy classes created by those methods.
jaroslav@601:  *
jaroslav@601:  * <p>To create a proxy for some interface {@code Foo}:
jaroslav@601:  * <pre>
jaroslav@601:  *     InvocationHandler handler = new MyInvocationHandler(...);
jaroslav@601:  *     Class proxyClass = Proxy.getProxyClass(
jaroslav@601:  *         Foo.class.getClassLoader(), new Class[] { Foo.class });
jaroslav@601:  *     Foo f = (Foo) proxyClass.
jaroslav@601:  *         getConstructor(new Class[] { InvocationHandler.class }).
jaroslav@601:  *         newInstance(new Object[] { handler });
jaroslav@601:  * </pre>
jaroslav@601:  * or more simply:
jaroslav@601:  * <pre>
jaroslav@601:  *     Foo f = (Foo) Proxy.newProxyInstance(Foo.class.getClassLoader(),
jaroslav@601:  *                                          new Class[] { Foo.class },
jaroslav@601:  *                                          handler);
jaroslav@601:  * </pre>
jaroslav@601:  *
jaroslav@601:  * <p>A <i>dynamic proxy class</i> (simply referred to as a <i>proxy
jaroslav@601:  * class</i> below) is a class that implements a list of interfaces
jaroslav@601:  * specified at runtime when the class is created, with behavior as
jaroslav@601:  * described below.
jaroslav@601:  *
jaroslav@601:  * A <i>proxy interface</i> is such an interface that is implemented
jaroslav@601:  * by a proxy class.
jaroslav@601:  *
jaroslav@601:  * A <i>proxy instance</i> is an instance of a proxy class.
jaroslav@601:  *
jaroslav@601:  * Each proxy instance has an associated <i>invocation handler</i>
jaroslav@601:  * object, which implements the interface {@link InvocationHandler}.
jaroslav@601:  * A method invocation on a proxy instance through one of its proxy
jaroslav@601:  * interfaces will be dispatched to the {@link InvocationHandler#invoke
jaroslav@601:  * invoke} method of the instance's invocation handler, passing the proxy
jaroslav@601:  * instance, a {@code java.lang.reflect.Method} object identifying
jaroslav@601:  * the method that was invoked, and an array of type {@code Object}
jaroslav@601:  * containing the arguments.  The invocation handler processes the
jaroslav@601:  * encoded method invocation as appropriate and the result that it
jaroslav@601:  * returns will be returned as the result of the method invocation on
jaroslav@601:  * the proxy instance.
jaroslav@601:  *
jaroslav@601:  * <p>A proxy class has the following properties:
jaroslav@601:  *
jaroslav@601:  * <ul>
jaroslav@601:  * <li>Proxy classes are public, final, and not abstract.
jaroslav@601:  *
jaroslav@601:  * <li>The unqualified name of a proxy class is unspecified.  The space
jaroslav@601:  * of class names that begin with the string {@code "$Proxy"}
jaroslav@601:  * should be, however, reserved for proxy classes.
jaroslav@601:  *
jaroslav@601:  * <li>A proxy class extends {@code java.lang.reflect.Proxy}.
jaroslav@601:  *
jaroslav@601:  * <li>A proxy class implements exactly the interfaces specified at its
jaroslav@601:  * creation, in the same order.
jaroslav@601:  *
jaroslav@601:  * <li>If a proxy class implements a non-public interface, then it will
jaroslav@601:  * be defined in the same package as that interface.  Otherwise, the
jaroslav@601:  * package of a proxy class is also unspecified.  Note that package
jaroslav@601:  * sealing will not prevent a proxy class from being successfully defined
jaroslav@601:  * in a particular package at runtime, and neither will classes already
jaroslav@601:  * defined by the same class loader and the same package with particular
jaroslav@601:  * signers.
jaroslav@601:  *
jaroslav@601:  * <li>Since a proxy class implements all of the interfaces specified at
jaroslav@601:  * its creation, invoking {@code getInterfaces} on its
jaroslav@601:  * {@code Class} object will return an array containing the same
jaroslav@601:  * list of interfaces (in the order specified at its creation), invoking
jaroslav@601:  * {@code getMethods} on its {@code Class} object will return
jaroslav@601:  * an array of {@code Method} objects that include all of the
jaroslav@601:  * methods in those interfaces, and invoking {@code getMethod} will
jaroslav@601:  * find methods in the proxy interfaces as would be expected.
jaroslav@601:  *
jaroslav@601:  * <li>The {@link Proxy#isProxyClass Proxy.isProxyClass} method will
jaroslav@601:  * return true if it is passed a proxy class-- a class returned by
jaroslav@601:  * {@code Proxy.getProxyClass} or the class of an object returned by
jaroslav@601:  * {@code Proxy.newProxyInstance}-- and false otherwise.
jaroslav@601:  *
jaroslav@601:  * <li>The {@code java.security.ProtectionDomain} of a proxy class
jaroslav@601:  * is the same as that of system classes loaded by the bootstrap class
jaroslav@601:  * loader, such as {@code java.lang.Object}, because the code for a
jaroslav@601:  * proxy class is generated by trusted system code.  This protection
jaroslav@601:  * domain will typically be granted
jaroslav@601:  * {@code java.security.AllPermission}.
jaroslav@601:  *
jaroslav@601:  * <li>Each proxy class has one public constructor that takes one argument,
jaroslav@601:  * an implementation of the interface {@link InvocationHandler}, to set
jaroslav@601:  * the invocation handler for a proxy instance.  Rather than having to use
jaroslav@601:  * the reflection API to access the public constructor, a proxy instance
jaroslav@601:  * can be also be created by calling the {@link Proxy#newProxyInstance
jaroslav@601:  * Proxy.newProxyInstance} method, which combines the actions of calling
jaroslav@601:  * {@link Proxy#getProxyClass Proxy.getProxyClass} with invoking the
jaroslav@601:  * constructor with an invocation handler.
jaroslav@601:  * </ul>
jaroslav@601:  *
jaroslav@601:  * <p>A proxy instance has the following properties:
jaroslav@601:  *
jaroslav@601:  * <ul>
jaroslav@601:  * <li>Given a proxy instance {@code proxy} and one of the
jaroslav@601:  * interfaces implemented by its proxy class {@code Foo}, the
jaroslav@601:  * following expression will return true:
jaroslav@601:  * <pre>
jaroslav@601:  *     {@code proxy instanceof Foo}
jaroslav@601:  * </pre>
jaroslav@601:  * and the following cast operation will succeed (rather than throwing
jaroslav@601:  * a {@code ClassCastException}):
jaroslav@601:  * <pre>
jaroslav@601:  *     {@code (Foo) proxy}
jaroslav@601:  * </pre>
jaroslav@601:  *
jaroslav@601:  * <li>Each proxy instance has an associated invocation handler, the one
jaroslav@601:  * that was passed to its constructor.  The static
jaroslav@601:  * {@link Proxy#getInvocationHandler Proxy.getInvocationHandler} method
jaroslav@601:  * will return the invocation handler associated with the proxy instance
jaroslav@601:  * passed as its argument.
jaroslav@601:  *
jaroslav@601:  * <li>An interface method invocation on a proxy instance will be
jaroslav@601:  * encoded and dispatched to the invocation handler's {@link
jaroslav@601:  * InvocationHandler#invoke invoke} method as described in the
jaroslav@601:  * documentation for that method.
jaroslav@601:  *
jaroslav@601:  * <li>An invocation of the {@code hashCode},
jaroslav@601:  * {@code equals}, or {@code toString} methods declared in
jaroslav@601:  * {@code java.lang.Object} on a proxy instance will be encoded and
jaroslav@601:  * dispatched to the invocation handler's {@code invoke} method in
jaroslav@601:  * the same manner as interface method invocations are encoded and
jaroslav@601:  * dispatched, as described above.  The declaring class of the
jaroslav@601:  * {@code Method} object passed to {@code invoke} will be
jaroslav@601:  * {@code java.lang.Object}.  Other public methods of a proxy
jaroslav@601:  * instance inherited from {@code java.lang.Object} are not
jaroslav@601:  * overridden by a proxy class, so invocations of those methods behave
jaroslav@601:  * like they do for instances of {@code java.lang.Object}.
jaroslav@601:  * </ul>
jaroslav@601:  *
jaroslav@601:  * <h3>Methods Duplicated in Multiple Proxy Interfaces</h3>
jaroslav@601:  *
jaroslav@601:  * <p>When two or more interfaces of a proxy class contain a method with
jaroslav@601:  * the same name and parameter signature, the order of the proxy class's
jaroslav@601:  * interfaces becomes significant.  When such a <i>duplicate method</i>
jaroslav@601:  * is invoked on a proxy instance, the {@code Method} object passed
jaroslav@601:  * to the invocation handler will not necessarily be the one whose
jaroslav@601:  * declaring class is assignable from the reference type of the interface
jaroslav@601:  * that the proxy's method was invoked through.  This limitation exists
jaroslav@601:  * because the corresponding method implementation in the generated proxy
jaroslav@601:  * class cannot determine which interface it was invoked through.
jaroslav@601:  * Therefore, when a duplicate method is invoked on a proxy instance,
jaroslav@601:  * the {@code Method} object for the method in the foremost interface
jaroslav@601:  * that contains the method (either directly or inherited through a
jaroslav@601:  * superinterface) in the proxy class's list of interfaces is passed to
jaroslav@601:  * the invocation handler's {@code invoke} method, regardless of the
jaroslav@601:  * reference type through which the method invocation occurred.
jaroslav@601:  *
jaroslav@601:  * <p>If a proxy interface contains a method with the same name and
jaroslav@601:  * parameter signature as the {@code hashCode}, {@code equals},
jaroslav@601:  * or {@code toString} methods of {@code java.lang.Object},
jaroslav@601:  * when such a method is invoked on a proxy instance, the
jaroslav@601:  * {@code Method} object passed to the invocation handler will have
jaroslav@601:  * {@code java.lang.Object} as its declaring class.  In other words,
jaroslav@601:  * the public, non-final methods of {@code java.lang.Object}
jaroslav@601:  * logically precede all of the proxy interfaces for the determination of
jaroslav@601:  * which {@code Method} object to pass to the invocation handler.
jaroslav@601:  *
jaroslav@601:  * <p>Note also that when a duplicate method is dispatched to an
jaroslav@601:  * invocation handler, the {@code invoke} method may only throw
jaroslav@601:  * checked exception types that are assignable to one of the exception
jaroslav@601:  * types in the {@code throws} clause of the method in <i>all</i> of
jaroslav@601:  * the proxy interfaces that it can be invoked through.  If the
jaroslav@601:  * {@code invoke} method throws a checked exception that is not
jaroslav@601:  * assignable to any of the exception types declared by the method in one
jaroslav@601:  * of the proxy interfaces that it can be invoked through, then an
jaroslav@601:  * unchecked {@code UndeclaredThrowableException} will be thrown by
jaroslav@601:  * the invocation on the proxy instance.  This restriction means that not
jaroslav@601:  * all of the exception types returned by invoking
jaroslav@601:  * {@code getExceptionTypes} on the {@code Method} object
jaroslav@601:  * passed to the {@code invoke} method can necessarily be thrown
jaroslav@601:  * successfully by the {@code invoke} method.
jaroslav@601:  *
jaroslav@601:  * @author      Peter Jones
jaroslav@601:  * @see         InvocationHandler
jaroslav@601:  * @since       1.3
jaroslav@601:  */
jaroslav@601: public class Proxy implements java.io.Serializable {
jaroslav@601: 
jaroslav@601:     private static final long serialVersionUID = -2222568056686623797L;
jaroslav@601: 
jaroslav@601: 
jaroslav@601: 
jaroslav@601:     /**
jaroslav@601:      * the invocation handler for this proxy instance.
jaroslav@601:      * @serial
jaroslav@601:      */
jaroslav@601:     protected InvocationHandler h;
jaroslav@601: 
jaroslav@601:     /**
jaroslav@601:      * Prohibits instantiation.
jaroslav@601:      */
jaroslav@601:     private Proxy() {
jaroslav@601:     }
jaroslav@601: 
jaroslav@601:     /**
jaroslav@601:      * Constructs a new {@code Proxy} instance from a subclass
jaroslav@601:      * (typically, a dynamic proxy class) with the specified value
jaroslav@601:      * for its invocation handler.
jaroslav@601:      *
jaroslav@601:      * @param   h the invocation handler for this proxy instance
jaroslav@601:      */
jaroslav@601:     protected Proxy(InvocationHandler h) {
jaroslav@601:         this.h = h;
jaroslav@601:     }
jaroslav@601: 
jaroslav@601:     /**
jaroslav@601:      * Returns the {@code java.lang.Class} object for a proxy class
jaroslav@601:      * given a class loader and an array of interfaces.  The proxy class
jaroslav@601:      * will be defined by the specified class loader and will implement
jaroslav@601:      * all of the supplied interfaces.  If a proxy class for the same
jaroslav@601:      * permutation of interfaces has already been defined by the class
jaroslav@601:      * loader, then the existing proxy class will be returned; otherwise,
jaroslav@601:      * a proxy class for those interfaces will be generated dynamically
jaroslav@601:      * and defined by the class loader.
jaroslav@601:      *
jaroslav@601:      * <p>There are several restrictions on the parameters that may be
jaroslav@601:      * passed to {@code Proxy.getProxyClass}:
jaroslav@601:      *
jaroslav@601:      * <ul>
jaroslav@601:      * <li>All of the {@code Class} objects in the
jaroslav@601:      * {@code interfaces} array must represent interfaces, not
jaroslav@601:      * classes or primitive types.
jaroslav@601:      *
jaroslav@601:      * <li>No two elements in the {@code interfaces} array may
jaroslav@601:      * refer to identical {@code Class} objects.
jaroslav@601:      *
jaroslav@601:      * <li>All of the interface types must be visible by name through the
jaroslav@601:      * specified class loader.  In other words, for class loader
jaroslav@601:      * {@code cl} and every interface {@code i}, the following
jaroslav@601:      * expression must be true:
jaroslav@601:      * <pre>
jaroslav@601:      *     Class.forName(i.getName(), false, cl) == i
jaroslav@601:      * </pre>
jaroslav@601:      *
jaroslav@601:      * <li>All non-public interfaces must be in the same package;
jaroslav@601:      * otherwise, it would not be possible for the proxy class to
jaroslav@601:      * implement all of the interfaces, regardless of what package it is
jaroslav@601:      * defined in.
jaroslav@601:      *
jaroslav@601:      * <li>For any set of member methods of the specified interfaces
jaroslav@601:      * that have the same signature:
jaroslav@601:      * <ul>
jaroslav@601:      * <li>If the return type of any of the methods is a primitive
jaroslav@601:      * type or void, then all of the methods must have that same
jaroslav@601:      * return type.
jaroslav@601:      * <li>Otherwise, one of the methods must have a return type that
jaroslav@601:      * is assignable to all of the return types of the rest of the
jaroslav@601:      * methods.
jaroslav@601:      * </ul>
jaroslav@601:      *
jaroslav@601:      * <li>The resulting proxy class must not exceed any limits imposed
jaroslav@601:      * on classes by the virtual machine.  For example, the VM may limit
jaroslav@601:      * the number of interfaces that a class may implement to 65535; in
jaroslav@601:      * that case, the size of the {@code interfaces} array must not
jaroslav@601:      * exceed 65535.
jaroslav@601:      * </ul>
jaroslav@601:      *
jaroslav@601:      * <p>If any of these restrictions are violated,
jaroslav@601:      * {@code Proxy.getProxyClass} will throw an
jaroslav@601:      * {@code IllegalArgumentException}.  If the {@code interfaces}
jaroslav@601:      * array argument or any of its elements are {@code null}, a
jaroslav@601:      * {@code NullPointerException} will be thrown.
jaroslav@601:      *
jaroslav@601:      * <p>Note that the order of the specified proxy interfaces is
jaroslav@601:      * significant: two requests for a proxy class with the same combination
jaroslav@601:      * of interfaces but in a different order will result in two distinct
jaroslav@601:      * proxy classes.
jaroslav@601:      *
jaroslav@601:      * @param   loader the class loader to define the proxy class
jaroslav@601:      * @param   interfaces the list of interfaces for the proxy class
jaroslav@601:      *          to implement
jaroslav@601:      * @return  a proxy class that is defined in the specified class loader
jaroslav@601:      *          and that implements the specified interfaces
jaroslav@601:      * @throws  IllegalArgumentException if any of the restrictions on the
jaroslav@601:      *          parameters that may be passed to {@code getProxyClass}
jaroslav@601:      *          are violated
jaroslav@601:      * @throws  NullPointerException if the {@code interfaces} array
jaroslav@601:      *          argument or any of its elements are {@code null}
jaroslav@601:      */
jaroslav@601:     public static Class<?> getProxyClass(ClassLoader loader,
jaroslav@601:                                          Class<?>... interfaces)
jaroslav@601:         throws IllegalArgumentException
jaroslav@601:     {
jaroslav@604:         throw new IllegalArgumentException();
jaroslav@601:     }
jaroslav@601: 
jaroslav@601:     /**
jaroslav@601:      * Returns an instance of a proxy class for the specified interfaces
jaroslav@601:      * that dispatches method invocations to the specified invocation
jaroslav@601:      * handler.  This method is equivalent to:
jaroslav@601:      * <pre>
jaroslav@601:      *     Proxy.getProxyClass(loader, interfaces).
jaroslav@601:      *         getConstructor(new Class[] { InvocationHandler.class }).
jaroslav@601:      *         newInstance(new Object[] { handler });
jaroslav@601:      * </pre>
jaroslav@601:      *
jaroslav@601:      * <p>{@code Proxy.newProxyInstance} throws
jaroslav@601:      * {@code IllegalArgumentException} for the same reasons that
jaroslav@601:      * {@code Proxy.getProxyClass} does.
jaroslav@601:      *
jaroslav@601:      * @param   loader the class loader to define the proxy class
jaroslav@601:      * @param   interfaces the list of interfaces for the proxy class
jaroslav@601:      *          to implement
jaroslav@601:      * @param   h the invocation handler to dispatch method invocations to
jaroslav@601:      * @return  a proxy instance with the specified invocation handler of a
jaroslav@601:      *          proxy class that is defined by the specified class loader
jaroslav@601:      *          and that implements the specified interfaces
jaroslav@601:      * @throws  IllegalArgumentException if any of the restrictions on the
jaroslav@601:      *          parameters that may be passed to {@code getProxyClass}
jaroslav@601:      *          are violated
jaroslav@601:      * @throws  NullPointerException if the {@code interfaces} array
jaroslav@601:      *          argument or any of its elements are {@code null}, or
jaroslav@601:      *          if the invocation handler, {@code h}, is
jaroslav@601:      *          {@code null}
jaroslav@601:      */
jaroslav@601:     public static Object newProxyInstance(ClassLoader loader,
jaroslav@601:                                           Class<?>[] interfaces,
jaroslav@601:                                           InvocationHandler h)
jaroslav@601:         throws IllegalArgumentException
jaroslav@601:     {
jaroslav@601:         if (h == null) {
jaroslav@601:             throw new NullPointerException();
jaroslav@601:         }
jaroslav@604:         throw new IllegalArgumentException();
jaroslav@601:     }
jaroslav@601: 
jaroslav@601:     /**
jaroslav@601:      * Returns true if and only if the specified class was dynamically
jaroslav@601:      * generated to be a proxy class using the {@code getProxyClass}
jaroslav@601:      * method or the {@code newProxyInstance} method.
jaroslav@601:      *
jaroslav@601:      * <p>The reliability of this method is important for the ability
jaroslav@601:      * to use it to make security decisions, so its implementation should
jaroslav@601:      * not just test if the class in question extends {@code Proxy}.
jaroslav@601:      *
jaroslav@601:      * @param   cl the class to test
jaroslav@601:      * @return  {@code true} if the class is a proxy class and
jaroslav@601:      *          {@code false} otherwise
jaroslav@601:      * @throws  NullPointerException if {@code cl} is {@code null}
jaroslav@601:      */
jaroslav@601:     public static boolean isProxyClass(Class<?> cl) {
jaroslav@601:         if (cl == null) {
jaroslav@601:             throw new NullPointerException();
jaroslav@601:         }
jaroslav@601: 
jaroslav@604:         return false;
jaroslav@601:     }
jaroslav@601: 
jaroslav@601:     /**
jaroslav@601:      * Returns the invocation handler for the specified proxy instance.
jaroslav@601:      *
jaroslav@601:      * @param   proxy the proxy instance to return the invocation handler for
jaroslav@601:      * @return  the invocation handler for the proxy instance
jaroslav@601:      * @throws  IllegalArgumentException if the argument is not a
jaroslav@601:      *          proxy instance
jaroslav@601:      */
jaroslav@601:     public static InvocationHandler getInvocationHandler(Object proxy)
jaroslav@601:         throws IllegalArgumentException
jaroslav@601:     {
jaroslav@601:         /*
jaroslav@601:          * Verify that the object is actually a proxy instance.
jaroslav@601:          */
jaroslav@601:         if (!isProxyClass(proxy.getClass())) {
jaroslav@601:             throw new IllegalArgumentException("not a proxy instance");
jaroslav@601:         }
jaroslav@601: 
jaroslav@601:         Proxy p = (Proxy) proxy;
jaroslav@601:         return p.h;
jaroslav@601:     }
jaroslav@601: 
jaroslav@601:     private static native Class defineClass0(ClassLoader loader, String name,
jaroslav@601:                                              byte[] b, int off, int len);
jaroslav@601: }