/*

 * Copyright (c) 1999, 2021, 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;

import java.lang.invoke.MethodHandle;

import java.lang.invoke.MethodHandles;

import java.lang.invoke.MethodType;

import java.lang.invoke.WrongMethodTypeException;

import java.lang.module.ModuleDescriptor;

import java.security.AccessController;

import java.security.PrivilegedAction;

import java.util.ArrayDeque;

import java.util.Arrays;

import java.util.Collections;

import java.util.Deque;

import java.util.HashMap;

import java.util.HashSet;

import java.util.IdentityHashMap;

import java.util.List;

import java.util.Map;

import java.util.Objects;

import java.util.Set;

import java.util.concurrent.ConcurrentHashMap;

import java.util.concurrent.atomic.AtomicInteger;

import java.util.concurrent.atomic.AtomicLong;

import java.util.function.BooleanSupplier;

import jdk.internal.access.JavaLangAccess;

import jdk.internal.access.SharedSecrets;

import jdk.internal.module.Modules;

import jdk.internal.misc.VM;

import jdk.internal.reflect.CallerSensitive;

import jdk.internal.reflect.Reflection;

import jdk.internal.loader.ClassLoaderValue;

import jdk.internal.vm.annotation.Stable;

import sun.reflect.misc.ReflectUtil;

import sun.security.action.GetPropertyAction;

import sun.security.util.SecurityConstants;

import static java.lang.invoke.MethodType.methodType;

import static java.lang.module.ModuleDescriptor.Modifier.SYNTHETIC;

/**

 *

 * {@code Proxy} provides static methods for creating objects that act like instances

 * of interfaces but allow for customized method invocation.

 * To create a proxy instance for some interface {@code Foo}:

 * <pre>{@code

 *     InvocationHandler handler = new MyInvocationHandler(...);

 *     Foo f = (Foo) Proxy.newProxyInstance(Foo.class.getClassLoader(),

 *                                          new Class<?>[] { Foo.class },

 *                                          handler);

 * }</pre>

 *

 * <p>

 * A <em>proxy class</em> is a class created at runtime that implements a specified

 * list of interfaces, known as <em>proxy interfaces</em>. A <em>proxy instance</em>

 * is an instance of a proxy class.

 *

 * Each proxy instance has an associated <i>invocation handler</i>

 * object, which implements the interface {@link InvocationHandler}.

 * A method invocation on a proxy instance through one of its proxy

 * interfaces will be dispatched to the {@link InvocationHandler#invoke

 * invoke} method of the instance's invocation handler, passing the proxy

 * instance, a {@code java.lang.reflect.Method} object identifying

 * the method that was invoked, and an array of type {@code Object}

 * containing the arguments.  The invocation handler processes the

 * encoded method invocation as appropriate and the result that it

 * returns will be returned as the result of the method invocation on

 * the proxy instance.

 *

 * <p>A proxy class has the following properties:

 *

 * <ul>

 * <li>The unqualified name of a proxy class is unspecified.  The space

 * of class names that begin with the string {@code "$Proxy"}

 * should be, however, reserved for proxy classes.

 *

 * <li>The package and module in which a proxy class is defined is specified

 * <a href="#membership">below</a>.

 *

 * <li>A proxy class is <em>final and non-abstract</em>.

 *

 * <li>A proxy class extends {@code java.lang.reflect.Proxy}.

 *

 * <li>A proxy class implements exactly the interfaces specified at its

 * creation, in the same order. Invoking {@link Class#getInterfaces() getInterfaces}

 * on its {@code Class} object will return an array containing the same

 * list of interfaces (in the order specified at its creation), invoking

 * {@link Class#getMethods getMethods} on its {@code Class} object will return

 * an array of {@code Method} objects that include all of the

 * methods in those interfaces, and invoking {@code getMethod} will

 * find methods in the proxy interfaces as would be expected.

 *

 * <li>The {@link java.security.ProtectionDomain} of a proxy class

 * is the same as that of system classes loaded by the bootstrap class

 * loader, such as {@code java.lang.Object}, because the code for a

 * proxy class is generated by trusted system code.  This protection

 * domain will typically be granted {@code java.security.AllPermission}.

 *

 * <li>The {@link Proxy#isProxyClass Proxy.isProxyClass} method can be used

 * to determine if a given class is a proxy class.

 * </ul>

 *

 * <p>A proxy instance has the following properties:

 *

 * <ul>

 * <li>Given a proxy instance {@code proxy} and one of the

 * interfaces, {@code Foo}, implemented by its proxy class, the

 * following expression will return true:

 * <pre>

 *     {@code proxy instanceof Foo}

 * </pre>

 * and the following cast operation will succeed (rather than throwing

 * a {@code ClassCastException}):

 * <pre>

 *     {@code (Foo) proxy}

 * </pre>

 *

 * <li>Each proxy instance has an associated invocation handler, the one

 * that was passed to its constructor.  The static

 * {@link Proxy#getInvocationHandler Proxy.getInvocationHandler} method

 * will return the invocation handler associated with the proxy instance

 * passed as its argument.

 *

 * <li>An interface method invocation on a proxy instance will be

 * encoded and dispatched to the invocation handler's {@link

 * InvocationHandler#invoke invoke} method as described in the

 * documentation for that method.

 *

 * <li>A proxy interface may define a default method or inherit

 * a default method from its superinterface directly or indirectly.

 * An invocation handler can invoke a default method of a proxy interface

 * by calling {@link InvocationHandler#invokeDefault(Object, Method, Object...)

 * InvocationHandler::invokeDefault}.

 *

 * <li>An invocation of the {@code hashCode},

 * {@code equals}, or {@code toString} methods declared in

 * {@code java.lang.Object} on a proxy instance will be encoded and

 * dispatched to the invocation handler's {@code invoke} method in

 * the same manner as interface method invocations are encoded and

 * dispatched, as described above.  The declaring class of the

 * {@code Method} object passed to {@code invoke} will be

 * {@code java.lang.Object}.  Other public methods of a proxy

 * instance inherited from {@code java.lang.Object} are not

 * overridden by a proxy class, so invocations of those methods behave

 * like they do for instances of {@code java.lang.Object}.

 * </ul>

 *

 * <h2><a id="membership">Package and Module Membership of Proxy Class</a></h2>

 *

 * The package and module to which a proxy class belongs are chosen such that

 * the accessibility of the proxy class is in line with the accessibility of

 * the proxy interfaces. Specifically, the package and the module membership

 * of a proxy class defined via the

 * {@link Proxy#getProxyClass(ClassLoader, Class[])} or

 * {@link Proxy#newProxyInstance(ClassLoader, Class[], InvocationHandler)}

 * methods is specified as follows:

 *

 * <ol>

 * <li>If all the proxy interfaces are in <em>exported</em> or <em>open</em>

 *     packages:

 * <ol type="a">

 * <li>if all the proxy interfaces are <em>public</em>, then the proxy class is

 *     <em>public</em> in an unconditionally exported but non-open package.

 *     The name of the package and the module are unspecified.</li>

 *

 * <li>if at least one of all the proxy interfaces is <em>non-public</em>, then

 *     the proxy class is <em>non-public</em> in the package and module of the

 *     non-public interfaces. All the non-public interfaces must be in the same

 *     package and module; otherwise, proxying them is

 *     <a href="#restrictions">not possible</a>.</li>

 * </ol>

 * </li>

 * <li>If at least one proxy interface is in a package that is

 *     <em>non-exported</em> and <em>non-open</em>:

 * <ol type="a">

 * <li>if all the proxy interfaces are <em>public</em>, then the proxy class is

 *     <em>public</em> in a <em>non-exported</em>, <em>non-open</em> package of

 *     <a href="#dynamicmodule"><em>dynamic module</em>.</a>

 *     The names of the package and the module are unspecified.</li>

 *

 * <li>if at least one of all the proxy interfaces is <em>non-public</em>, then

 *     the proxy class is <em>non-public</em> in the package and module of the

 *     non-public interfaces. All the non-public interfaces must be in the same

 *     package and module; otherwise, proxying them is

 *     <a href="#restrictions">not possible</a>.</li>

 * </ol>

 * </li>

 * </ol>

 *

 * <p>

 * Note that if proxy interfaces with a mix of accessibilities -- for example,

 * an exported public interface and a non-exported non-public interface -- are

 * proxied by the same instance, then the proxy class's accessibility is

 * governed by the least accessible proxy interface.

 * <p>

 * Note that it is possible for arbitrary code to obtain access to a proxy class

 * in an open package with {@link AccessibleObject#setAccessible setAccessible},

 * whereas a proxy class in a non-open package is never accessible to

 * code outside the module of the proxy class.

 *

 * <p>

 * Throughout this specification, a "non-exported package" refers to a package

 * that is not exported to all modules, and a "non-open package" refers to

 * a package that is not open to all modules.  Specifically, these terms refer to

 * a package that either is not exported/open by its containing module or is

 * exported/open in a qualified fashion by its containing module.

 *

 * <h3><a id="dynamicmodule">Dynamic Modules</a></h3>

 * <p>

 * A dynamic module is a named module generated at runtime. A proxy class

 * defined in a dynamic module is encapsulated and not accessible to any module.

 * Calling {@link Constructor#newInstance(Object...)} on a proxy class in

 * a dynamic module will throw {@code IllegalAccessException};

 * {@code Proxy.newProxyInstance} method should be used instead.

 *

 * <p>

 * A dynamic module can read the modules of all of the superinterfaces of a proxy

 * class and the modules of the classes and interfaces referenced by

 * all public method signatures of a proxy class.  If a superinterface or

 * a referenced class or interface, say {@code T}, is in a non-exported package,

 * the {@linkplain Module module} of {@code T} is updated to export the

 * package of {@code T} to the dynamic module.

 *

 * <h3>Methods Duplicated in Multiple Proxy Interfaces</h3>

 *

 * <p>When two or more proxy interfaces contain a method with

 * the same name and parameter signature, the order of the proxy class's

 * interfaces becomes significant.  When such a <i>duplicate method</i>

 * is invoked on a proxy instance, the {@code Method} object passed

 * to the invocation handler will not necessarily be the one whose

 * declaring class is assignable from the reference type of the interface

 * that the proxy's method was invoked through.  This limitation exists

 * because the corresponding method implementation in the generated proxy

 * class cannot determine which interface it was invoked through.

 * Therefore, when a duplicate method is invoked on a proxy instance,

 * the {@code Method} object for the method in the foremost interface

 * that contains the method (either directly or inherited through a

 * superinterface) in the proxy class's list of interfaces is passed to

 * the invocation handler's {@code invoke} method, regardless of the

 * reference type through which the method invocation occurred.

 *

 * <p>If a proxy interface contains a method with the same name and

 * parameter signature as the {@code hashCode}, {@code equals},

 * or {@code toString} methods of {@code java.lang.Object},

 * when such a method is invoked on a proxy instance, the

 * {@code Method} object passed to the invocation handler will have

 * {@code java.lang.Object} as its declaring class.  In other words,

 * the public, non-final methods of {@code java.lang.Object}

 * logically precede all of the proxy interfaces for the determination of

 * which {@code Method} object to pass to the invocation handler.

 *

 * <p>Note also that when a duplicate method is dispatched to an

 * invocation handler, the {@code invoke} method may only throw

 * checked exception types that are assignable to one of the exception

 * types in the {@code throws} clause of the method in <i>all</i> of

 * the proxy interfaces that it can be invoked through.  If the

 * {@code invoke} method throws a checked exception that is not

 * assignable to any of the exception types declared by the method in one

 * of the proxy interfaces that it can be invoked through, then an

 * unchecked {@code UndeclaredThrowableException} will be thrown by

 * the invocation on the proxy instance.  This restriction means that not

 * all of the exception types returned by invoking

 * {@code getExceptionTypes} on the {@code Method} object

 * passed to the {@code invoke} method can necessarily be thrown

 * successfully by the {@code invoke} method.

 *

 * @author      Peter Jones

 * @see         InvocationHandler

 * @since       1.3

 * @revised 9

 */

public class Proxy implements java.io.Serializable {

    @java.io.Serial

    private static final long serialVersionUID = -2222568056686623797L;

    /** parameter types of a proxy class constructor */

    private static final Class<?>[] constructorParams =

        { InvocationHandler.class };

    /**

     * a cache of proxy constructors with

     * {@link Constructor#setAccessible(boolean) accessible} flag already set

     */

    private static final ClassLoaderValue<Constructor<?>> proxyCache =

        new ClassLoaderValue<>();

    /**

     * the invocation handler for this proxy instance.

     * @serial

     */

    @SuppressWarnings("serial") // Not statically typed as Serializable

    protected InvocationHandler h;

    /**

     * Prohibits instantiation.

     */

    private Proxy() {

    }

    /**

     * Constructs a new {@code Proxy} instance from a subclass

     * (typically, a dynamic proxy class) with the specified value

     * for its invocation handler.

     *

     * @param  h the invocation handler for this proxy instance

     *

     * @throws NullPointerException if the given invocation handler, {@code h},

     *         is {@code null}.

     */

    protected Proxy(InvocationHandler h) {

        Objects.requireNonNull(h);

        this.h = h;

    }

    /**

     * Returns the {@code java.lang.Class} object for a proxy class

     * given a class loader and an array of interfaces.  The proxy class

     * will be defined by the specified class loader and will implement

     * all of the supplied interfaces.  If any of the given interfaces

     * is non-public, the proxy class will be non-public. If a proxy class

     * for the same permutation of interfaces has already been defined by the

     * class loader, then the existing proxy class will be returned; otherwise,

     * a proxy class for those interfaces will be generated dynamically

     * and defined by the class loader.

     *

     * @param   loader the class loader to define the proxy class

     * @param   interfaces the list of interfaces for the proxy class

     *          to implement

     * @return  a proxy class that is defined in the specified class loader

     *          and that implements the specified interfaces

     * @throws  IllegalArgumentException if any of the <a href="#restrictions">

     *          restrictions</a> on the parameters are violated

     * @throws  SecurityException if a security manager, <em>s</em>, is present

     *          and any of the following conditions is met:

     *          <ul>

     *             <li> the given {@code loader} is {@code null} and

     *             the caller's class loader is not {@code null} and the

     *             invocation of {@link SecurityManager#checkPermission

     *             s.checkPermission} with

     *             {@code RuntimePermission("getClassLoader")} permission

     *             denies access.</li>

     *             <li> for each proxy interface, {@code intf},

     *             the caller's class loader is not the same as or an

     *             ancestor of the class loader for {@code intf} and

     *             invocation of {@link SecurityManager#checkPackageAccess

     *             s.checkPackageAccess()} denies access to {@code intf}.</li>

     *          </ul>

     * @throws  NullPointerException if the {@code interfaces} array

     *          argument or any of its elements are {@code null}

     *

     * @deprecated Proxy classes generated in a named module are encapsulated

     *      and not accessible to code outside its module.

     *      {@link Constructor#newInstance(Object...) Constructor.newInstance}

     *      will throw {@code IllegalAccessException} when it is called on

     *      an inaccessible proxy class.

     *      Use {@link #newProxyInstance(ClassLoader, Class[], InvocationHandler)}

     *      to create a proxy instance instead.

     *

     * @see <a href="#membership">Package and Module Membership of Proxy Class</a>

     * @revised 9

     */

    @Deprecated

    @CallerSensitive

    public static Class<?> getProxyClass(ClassLoader loader,

                                         Class<?>... interfaces)

        throws IllegalArgumentException

    {

        @SuppressWarnings("removal")

        Class<?> caller = System.getSecurityManager() == null

                              ? null

                              : Reflection.getCallerClass();

        return getProxyConstructor(caller, loader, interfaces)

            .getDeclaringClass();

    }

    /**

     * Returns the {@code Constructor} object of a proxy class that takes a

     * single argument of type {@link InvocationHandler}, given a class loader

     * and an array of interfaces. The returned constructor will have the

     * {@link Constructor#setAccessible(boolean) accessible} flag already set.

     *

     * @param   caller passed from a public-facing @CallerSensitive method if

     *                 SecurityManager is set or {@code null} if there's no

     *                 SecurityManager

     * @param   loader the class loader to define the proxy class

     * @param   interfaces the list of interfaces for the proxy class

     *          to implement

     * @return  a Constructor of the proxy class taking single

     *          {@code InvocationHandler} parameter

     */

    private static Constructor<?> getProxyConstructor(Class<?> caller,

                                                      ClassLoader loader,

                                                      Class<?>... interfaces)

    {

        // optimization for single interface

        if (interfaces.length == 1) {

            Class<?> intf = interfaces[0];

            if (caller != null) {

                checkProxyAccess(caller, loader, intf);

            }

            return proxyCache.sub(intf).computeIfAbsent(

                loader,

                (ld, clv) -> new ProxyBuilder(ld, clv.key()).build()

            );

        } else {

            // interfaces cloned

            final Class<?>[] intfsArray = interfaces.clone();

            if (caller != null) {

                checkProxyAccess(caller, loader, intfsArray);

            }

            final List<Class<?>> intfs = Arrays.asList(intfsArray);

            return proxyCache.sub(intfs).computeIfAbsent(

                loader,

                (ld, clv) -> new ProxyBuilder(ld, clv.key()).build()

            );

        }

    }

    /*

     * Check permissions required to create a Proxy class.

     *

     * To define a proxy class, it performs the access checks as in

     * Class.forName (VM will invoke ClassLoader.checkPackageAccess):

     * 1. "getClassLoader" permission check if loader == null

     * 2. checkPackageAccess on the interfaces it implements

     *

     * To get a constructor and new instance of a proxy class, it performs

     * the package access check on the interfaces it implements

     * as in Class.getConstructor.

     *

     * If an interface is non-public, the proxy class must be defined by

     * the defining loader of the interface.  If the caller's class loader

     * is not the same as the defining loader of the interface, the VM

     * will throw IllegalAccessError when the generated proxy class is

     * being defined.

     */

    private static void checkProxyAccess(Class<?> caller,

                                         ClassLoader loader,

                                         Class<?> ... interfaces)

    {

        @SuppressWarnings("removal")

        SecurityManager sm = System.getSecurityManager();

        if (sm != null) {

            ClassLoader ccl = caller.getClassLoader();

            if (loader == null && ccl != null) {

                sm.checkPermission(SecurityConstants.GET_CLASSLOADER_PERMISSION);

            }

            ReflectUtil.checkProxyPackageAccess(ccl, interfaces);

        }

    }

    /**

     * Builder for a proxy class.

     *

     * If the module is not specified in this ProxyBuilder constructor,

     * it will map from the given loader and interfaces to the module

     * in which the proxy class will be defined.

     */

    private static final class ProxyBuilder {

        private static final JavaLangAccess JLA = SharedSecrets.getJavaLangAccess();

        // prefix for all proxy class names

        private static final String proxyClassNamePrefix = "$Proxy";

        // next number to use for generation of unique proxy class names

        private static final AtomicLong nextUniqueNumber = new AtomicLong();

        // a reverse cache of defined proxy classes

        private static final ClassLoaderValue<Boolean> reverseProxyCache =

            new ClassLoaderValue<>();

        private static Class<?> defineProxyClass(Module m, List<Class<?>> interfaces) {

            String proxyPkg = null;     // package to define proxy class in

            int accessFlags = Modifier.PUBLIC | Modifier.FINAL;

            boolean nonExported = false;

            /*

             * Record the package of a non-public proxy interface so that the

             * proxy class will be defined in the same package.  Verify that

             * all non-public proxy interfaces are in the same package.

             */

            for (Class<?> intf : interfaces) {

                int flags = intf.getModifiers();

                if (!Modifier.isPublic(flags)) {

                    accessFlags = Modifier.FINAL;  // non-public, final

                    String pkg = intf.getPackageName();

                    if (proxyPkg == null) {

                        proxyPkg = pkg;

                    } else if (!pkg.equals(proxyPkg)) {

                        throw new IllegalArgumentException(

                                "non-public interfaces from different packages");

                    }

                } else {

                    if (!intf.getModule().isExported(intf.getPackageName())) {

                        // module-private types

                        nonExported = true;

                    }

                }

            }

            if (proxyPkg == null) {

                // all proxy interfaces are public and exported

                if (!m.isNamed())

                    throw new InternalError("ununamed module: " + m);

                proxyPkg = nonExported ? PROXY_PACKAGE_PREFIX + "." + m.getName()

                                       : m.getName();

            } else if (proxyPkg.isEmpty() && m.isNamed()) {

                throw new IllegalArgumentException(

                        "Unnamed package cannot be added to " + m);

            }

            if (m.isNamed()) {

                if (!m.getDescriptor().packages().contains(proxyPkg)) {

                    throw new InternalError(proxyPkg + " not exist in " + m.getName());

                }

            }

            /*

             * Choose a name for the proxy class to generate.

             */

            long num = nextUniqueNumber.getAndIncrement();

            String proxyName = proxyPkg.isEmpty()

                                    ? proxyClassNamePrefix + num

                                    : proxyPkg + "." + proxyClassNamePrefix + num;

            ClassLoader loader = getLoader(m);

            trace(proxyName, m, loader, interfaces);

            /*

             * Generate the specified proxy class.

             */

            byte[] proxyClassFile = ProxyGenerator.generateProxyClass(loader, proxyName, interfaces, accessFlags);

            try {

                Class<?> pc = JLA.defineClass(loader, proxyName, proxyClassFile,

                                              null, "__dynamic_proxy__");

                reverseProxyCache.sub(pc).putIfAbsent(loader, Boolean.TRUE);

                return pc;

            } catch (ClassFormatError e) {

                /*

                 * A ClassFormatError here means that (barring bugs in the

                 * proxy class generation code) there was some other

                 * invalid aspect of the arguments supplied to the proxy

                 * class creation (such as virtual machine limitations

                 * exceeded).

                 */

                throw new IllegalArgumentException(e.toString());

            }

        }

        /**

         * Test if given class is a class defined by

         * {@link #defineProxyClass(Module, List)}

         */

        static boolean isProxyClass(Class<?> c) {

            return Objects.equals(reverseProxyCache.sub(c).get(c.getClassLoader()),

                                  Boolean.TRUE);

        }

        private static boolean isExportedType(Class<?> c) {

            String pn = c.getPackageName();

            return Modifier.isPublic(c.getModifiers()) && c.getModule().isExported(pn);

        }

        private static boolean isPackagePrivateType(Class<?> c) {

            return !Modifier.isPublic(c.getModifiers());

        }

        private static String toDetails(Class<?> c) {

            String access = "unknown";

            if (isExportedType(c)) {

                access = "exported";

            } else if (isPackagePrivateType(c)) {

                access = "package-private";

            } else {

                access = "module-private";

            }

            ClassLoader ld = c.getClassLoader();

            return String.format("   %s/%s %s loader %s",

                    c.getModule().getName(), c.getName(), access, ld);

        }

        static void trace(String cn,

                          Module module,

                          ClassLoader loader,

                          List<Class<?>> interfaces) {

            if (isDebug()) {

                System.err.format("PROXY: %s/%s defined by %s%n",

                                  module.getName(), cn, loader);

            }

            if (isDebug("debug")) {

                interfaces.forEach(c -> System.out.println(toDetails(c)));

            }

        }

        private static final String DEBUG =

            GetPropertyAction.privilegedGetProperty("jdk.proxy.debug", "");

        private static boolean isDebug() {

            return !DEBUG.isEmpty();

        }

        private static boolean isDebug(String flag) {

            return DEBUG.equals(flag);

        }

        // ProxyBuilder instance members start here....

        private final List<Class<?>> interfaces;

        private final Module module;

        ProxyBuilder(ClassLoader loader, List<Class<?>> interfaces) {

            if (!VM.isModuleSystemInited()) {

                throw new InternalError("Proxy is not supported until "

                        + "module system is fully initialized");

            }

            if (interfaces.size() > 65535) {

                throw new IllegalArgumentException("interface limit exceeded: "

                        + interfaces.size());

            }

            Set<Class<?>> refTypes = referencedTypes(loader, interfaces);

            // IAE if violates any restrictions specified in newProxyInstance

            validateProxyInterfaces(loader, interfaces, refTypes);

            this.interfaces = interfaces;

            this.module = mapToModule(loader, interfaces, refTypes);

            assert getLoader(module) == loader;

        }

        ProxyBuilder(ClassLoader loader, Class<?> intf) {

            this(loader, Collections.singletonList(intf));

        }

        /**

         * Generate a proxy class and return its proxy Constructor with

         * accessible flag already set. If the target module does not have access

         * to any interface types, IllegalAccessError will be thrown by the VM

         * at defineClass time.

         *

         * Must call the checkProxyAccess method to perform permission checks

         * before calling this.

         */

        @SuppressWarnings("removal")

        Constructor<?> build() {

            Class<?> proxyClass = defineProxyClass(module, interfaces);

            assert !module.isNamed() || module.isOpen(proxyClass.getPackageName(), Proxy.class.getModule());

            final Constructor<?> cons;

            try {

                cons = proxyClass.getConstructor(constructorParams);

            } catch (NoSuchMethodException e) {

                throw new InternalError(e.toString(), e);

            }

            AccessController.doPrivileged(new PrivilegedAction<Void>() {

                public Void run() {

                    cons.setAccessible(true);

                    return null;

                }

            });

            return cons;

        }

        /**

         * Validate the given proxy interfaces and the given referenced types

         * are visible to the defining loader.

         *

         * @throws IllegalArgumentException if it violates the restrictions

         *         specified in {@link Proxy#newProxyInstance}

         */

        private static void validateProxyInterfaces(ClassLoader loader,

                                                    List<Class<?>> interfaces,

                                                    Set<Class<?>> refTypes)

        {

            Map<Class<?>, Boolean> interfaceSet = new IdentityHashMap<>(interfaces.size());

            for (Class<?> intf : interfaces) {

                /*

                 * Verify that the Class object actually represents an

                 * interface.

                 */

                if (!intf.isInterface()) {

                    throw new IllegalArgumentException(intf.getName() + " is not an interface");

                }

                if (intf.isHidden()) {

                    throw new IllegalArgumentException(intf.getName() + " is a hidden interface");

                }

                if (intf.isSealed()) {

                    throw new IllegalArgumentException(intf.getName() + " is a sealed interface");

                }

                /*

                 * Verify that the class loader resolves the name of this

                 * interface to the same Class object.

                 */

                ensureVisible(loader, intf);

                /*

                 * Verify that this interface is not a duplicate.

                 */

                if (interfaceSet.put(intf, Boolean.TRUE) != null) {

                    throw new IllegalArgumentException("repeated interface: " + intf.getName());

                }

            }

            for (Class<?> type : refTypes) {

                ensureVisible(loader, type);

            }

        }

        /*

         * Returns all types referenced by all public non-static method signatures of

         * the proxy interfaces

         */

        private static Set<Class<?>> referencedTypes(ClassLoader loader,

                                                     List<Class<?>> interfaces) {

            var types = new HashSet<Class<?>>();

            for (var intf : interfaces) {

                for (Method m : intf.getMethods()) {

                    if (!Modifier.isStatic(m.getModifiers())) {

                        addElementType(types, m.getReturnType());

                        addElementTypes(types, m.getSharedParameterTypes());

                        addElementTypes(types, m.getSharedExceptionTypes());

                    }

                }

            }

            return types;

        }

        private static void addElementTypes(HashSet<Class<?>> types,

                                            Class<?> ... classes) {

            for (var cls : classes) {

                addElementType(types, cls);

            }

        }

        private static void addElementType(HashSet<Class<?>> types,

                                           Class<?> cls) {

            var type = getElementType(cls);

            if (!type.isPrimitive()) {

                types.add(type);

            }

        }

        /**

         * Returns the module that the generated proxy class belongs to.

         *

         * If any of proxy interface is package-private, then the proxy class

         * is in the same module of the package-private interface.

         *

         * If all proxy interfaces are public and in exported packages,

         * then the proxy class is in a dynamic module in an unconditionally

         * exported package.

         *

         * If all proxy interfaces are public and at least one in a non-exported

         * package, then the proxy class is in a dynamic module in a

         * non-exported package.

         *

         * The package of proxy class is open to java.base for deep reflective access.

         *

         * Reads edge and qualified exports are added for dynamic module to access.

         */

        private static Module mapToModule(ClassLoader loader,

                                          List<Class<?>> interfaces,

                                          Set<Class<?>> refTypes) {

            Map<Class<?>, Module> packagePrivateTypes = new HashMap<>();

            for (Class<?> intf : interfaces) {

                Module m = intf.getModule();

                if (!Modifier.isPublic(intf.getModifiers())) {

                    packagePrivateTypes.put(intf, m);

                }

            }

            if (packagePrivateTypes.size() > 0) {

                // all package-private types must be in the same runtime package

                // i.e. same package name and same module (named or unnamed)

                //

                // Configuration will fail if M1 and in M2 defined by the same loader

                // and both have the same package p (so no need to check class loader)

                Module targetModule = null;

                String targetPackageName = null;

                for (Map.Entry<Class<?>, Module> e : packagePrivateTypes.entrySet()) {

                    Class<?> intf = e.getKey();

                    Module m = e.getValue();

                    if ((targetModule != null && targetModule != m) ||

                        (targetPackageName != null && targetPackageName != intf.getPackageName())) {

                        throw new IllegalArgumentException(

                                "cannot have non-public interfaces in different packages");

                    }

                    if (getLoader(m) != loader) {

                        // the specified loader is not the same class loader

                        // of the non-public interface

                        throw new IllegalArgumentException(

                                "non-public interface is not defined by the given loader");

                    }

                    targetModule = m;

                    targetPackageName = e.getKey().getPackageName();

                }

                // validate if the target module can access all other interfaces

                for (Class<?> intf : interfaces) {

                    Module m = intf.getModule();

                    if (m == targetModule) continue;

                    if (!targetModule.canRead(m) || !m.isExported(intf.getPackageName(), targetModule)) {

                        throw new IllegalArgumentException(targetModule + " can't access " + intf.getName());

                    }

                }

                // opens the package of the non-public proxy class for java.base to access

                if (targetModule.isNamed()) {

                    Modules.addOpens(targetModule, targetPackageName, Proxy.class.getModule());

                }

                // return the module of the package-private interface

                return targetModule;

            }

            // All proxy interfaces are public.  So maps to a dynamic proxy module

            // and add reads edge and qualified exports, if necessary

            Module targetModule = getDynamicModule(loader);

            // set up proxy class access to proxy interfaces and types

            // referenced in the method signature

            Set<Class<?>> types = new HashSet<>(interfaces);

            types.addAll(refTypes);

            for (Class<?> c : types) {

                ensureAccess(targetModule, c);

            }

            return targetModule;

        }

        /*

         * Ensure the given module can access the given class.

         */

        private static void ensureAccess(Module target, Class<?> c) {

            Module m = c.getModule();

            // add read edge and qualified export for the target module to access

            if (!target.canRead(m)) {

                Modules.addReads(target, m);

            }

            String pn = c.getPackageName();

            if (!m.isExported(pn, target)) {

                Modules.addExports(m, pn, target);

            }

        }

        /*

         * Ensure the given class is visible to the class loader.

         */

        private static void ensureVisible(ClassLoader ld, Class<?> c) {

            Class<?> type = null;

            try {

                type = Class.forName(c.getName(), false, ld);

            } catch (ClassNotFoundException e) {

            }

            if (type != c) {

                throw new IllegalArgumentException(c.getName() +

                        " referenced from a method is not visible from class loader");

            }

        }

        private static Class<?> getElementType(Class<?> type) {

            Class<?> e = type;

            while (e.isArray()) {

                e = e.getComponentType();

            }

            return e;

        }

        private static final ClassLoaderValue<Module> dynProxyModules =

            new ClassLoaderValue<>();

        private static final AtomicInteger counter = new AtomicInteger();

        /*

         * Define a dynamic module with a packge named $MODULE which

         * is unconditionally exported and another package named

         * com.sun.proxy.$MODULE which is encapsulated.

         *

         * Each class loader will have one dynamic module.

         */

        private static Module getDynamicModule(ClassLoader loader) {

            return dynProxyModules.computeIfAbsent(loader, (ld, clv) -> {

                // create a dynamic module and setup module access

                String mn = "jdk.proxy" + counter.incrementAndGet();

                String pn = PROXY_PACKAGE_PREFIX + "." + mn;

                ModuleDescriptor descriptor =

                        ModuleDescriptor.newModule(mn, Set.of(SYNTHETIC))

                                        .packages(Set.of(pn, mn))

                                        .exports(mn)

                                        .build();

                Module m = Modules.defineModule(ld, descriptor, null);

                Modules.addReads(m, Proxy.class.getModule());

                Modules.addExports(m, mn);

                // java.base to create proxy instance and access its Lookup instance

                Modules.addOpens(m, pn, Proxy.class.getModule());

                Modules.addOpens(m, mn, Proxy.class.getModule());

                return m;

            });

        }

    }

    /**

     * Returns a proxy instance for the specified interfaces

     * that dispatches method invocations to the specified invocation

     * handler.

     * <p>

     * <a id="restrictions">{@code IllegalArgumentException} will be thrown

     * if any of the following restrictions is violated:</a>

     * <ul>

     * <li>All of {@code Class} objects in the given {@code interfaces} array

     * must represent {@linkplain Class#isHidden() non-hidden} and

     * {@linkplain Class#isSealed() non-sealed} interfaces,

     * not classes or primitive types.

     *

     * <li>No two elements in the {@code interfaces} array may

     * refer to identical {@code Class} objects.

     *

     * <li>All of the interface types must be visible by name through the

     * specified class loader. In other words, for class loader

     * {@code cl} and every interface {@code i}, the following

     * expression must be true:<p>

     * {@code Class.forName(i.getName(), false, cl) == i}

     *

     * <li>All of the types referenced by all

     * public method signatures of the specified interfaces

     * and those inherited by their superinterfaces

     * must be visible by name through the specified class loader.

     *

     * <li>All non-public interfaces must be in the same package

     * and module, defined by the specified class loader and

     * the module of the non-public interfaces can access all of

     * the interface types; otherwise, it would not be possible for

     * the proxy class to implement all of the interfaces,

     * regardless of what package it is defined in.

     *

     * <li>For any set of member methods of the specified interfaces

     * that have the same signature:

     * <ul>

     * <li>If the return type of any of the methods is a primitive

     * type or void, then all of the methods must have that same

     * return type.

     * <li>Otherwise, one of the methods must have a return type that

     * is assignable to all of the return types of the rest of the

     * methods.

     * </ul>

     *

     * <li>The resulting proxy class must not exceed any limits imposed

     * on classes by the virtual machine.  For example, the VM may limit

     * the number of interfaces that a class may implement to 65535; in

     * that case, the size of the {@code interfaces} array must not

     * exceed 65535.

     * </ul>

     *

     * <p>Note that the order of the specified proxy interfaces is

     * significant: two requests for a proxy class with the same combination

     * of interfaces but in a different order will result in two distinct

     * proxy classes.

     *

     * @param   loader the class loader to define the proxy class

     * @param   interfaces the list of interfaces for the proxy class

     *          to implement

     * @param   h the invocation handler to dispatch method invocations to

     * @return  a proxy instance with the specified invocation handler of a

     *          proxy class that is defined by the specified class loader

     *          and that implements the specified interfaces

     * @throws  IllegalArgumentException if any of the <a href="#restrictions">

     *          restrictions</a> on the parameters are violated

     * @throws  SecurityException if a security manager, <em>s</em>, is present

     *          and any of the following conditions is met:

     *          <ul>

     *          <li> the given {@code loader} is {@code null} and

     *               the caller's class loader is not {@code null} and the

     *               invocation of {@link SecurityManager#checkPermission

     *               s.checkPermission} with

     *               {@code RuntimePermission("getClassLoader")} permission

     *               denies access;</li>

     *          <li> for each proxy interface, {@code intf},

     *               the caller's class loader is not the same as or an

     *               ancestor of the class loader for {@code intf} and

     *               invocation of {@link SecurityManager#checkPackageAccess

     *               s.checkPackageAccess()} denies access to {@code intf};</li>

     *          <li> any of the given proxy interfaces is non-public and the

     *               caller class is not in the same {@linkplain Package runtime package}

     *               as the non-public interface and the invocation of

     *               {@link SecurityManager#checkPermission s.checkPermission} with

     *               {@code ReflectPermission("newProxyInPackage.{package name}")}

     *               permission denies access.</li>

     *          </ul>

     * @throws  NullPointerException if the {@code interfaces} array

     *          argument or any of its elements are {@code null}, or

     *          if the invocation handler, {@code h}, is

     *          {@code null}

     *

     * @see <a href="#membership">Package and Module Membership of Proxy Class</a>

     * @revised 9

     */

    @CallerSensitive

    public static Object newProxyInstance(ClassLoader loader,

                                          Class<?>[] interfaces,

                                          InvocationHandler h) {

        Objects.requireNonNull(h);

        @SuppressWarnings("removal")

        final Class<?> caller = System.getSecurityManager() == null

                                    ? null

                                    : Reflection.getCallerClass();

        /*

         * Look up or generate the designated proxy class and its constructor.

         */

        Constructor<?> cons = getProxyConstructor(caller, loader, interfaces);

        return newProxyInstance(caller, cons, h);

    }

    private static Object newProxyInstance(Class<?> caller, // null if no SecurityManager

                                           Constructor<?> cons,

                                           InvocationHandler h) {

        /*

         * Invoke its constructor with the designated invocation handler.

         */

        try {

            if (caller != null) {

                checkNewProxyPermission(caller, cons.getDeclaringClass());

            }

            return cons.newInstance(new Object[]{h});

        } catch (IllegalAccessException | InstantiationException e) {

            throw new InternalError(e.toString(), e);

        } catch (InvocationTargetException e) {

            Throwable t = e.getCause();

            if (t instanceof RuntimeException) {

                throw (RuntimeException) t;

            } else {

                throw new InternalError(t.toString(), t);

            }

        }

    }

    private static void checkNewProxyPermission(Class<?> caller, Class<?> proxyClass) {

        @SuppressWarnings("removal")

        SecurityManager sm = System.getSecurityManager();

        if (sm != null) {

            if (ReflectUtil.isNonPublicProxyClass(proxyClass)) {

                ClassLoader ccl = caller.getClassLoader();

                ClassLoader pcl = proxyClass.getClassLoader();

                // do permission check if the caller is in a different runtime package

                // of the proxy class

                String pkg = proxyClass.getPackageName();

                String callerPkg = caller.getPackageName();

                if (pcl != ccl || !pkg.equals(callerPkg)) {

                    sm.checkPermission(new ReflectPermission("newProxyInPackage." + pkg));

                }

            }

        }

    }

    /**

     * Returns the class loader for the given module.

     */

    @SuppressWarnings("removal")

    private static ClassLoader getLoader(Module m) {

        PrivilegedAction<ClassLoader> pa = m::getClassLoader;

        return AccessController.doPrivileged(pa);

    }

    /**

     * Returns true if the given class is a proxy class.

     *

     * @implNote The reliability of this method is important for the ability

     * to use it to make security decisions, so its implementation should

     * not just test if the class in question extends {@code Proxy}.

     *

     * @param   cl the class to test

     * @return  {@code true} if the class is a proxy class and

     *          {@code false} otherwise

     * @throws  NullPointerException if {@code cl} is {@code null}

     *

     * @revised 9

     */

    public static boolean isProxyClass(Class<?> cl) {

        return Proxy.class.isAssignableFrom(cl) && ProxyBuilder.isProxyClass(cl);

    }

    /**

     * Returns the invocation handler for the specified proxy instance.

     *

     * @param   proxy the proxy instance to return the invocation handler for

     * @return  the invocation handler for the proxy instance

     * @throws  IllegalArgumentException if the argument is not a

     *          proxy instance

     * @throws  SecurityException if a security manager, <em>s</em>, is present

     *          and the caller's class loader is not the same as or an

     *          ancestor of the class loader for the invocation handler

     *          and invocation of {@link SecurityManager#checkPackageAccess

     *          s.checkPackageAccess()} denies access to the invocation

     *          handler's class.

     */

    @SuppressWarnings("removal")

    @CallerSensitive

    public static InvocationHandler getInvocationHandler(Object proxy)

        throws IllegalArgumentException

    {

        /*

         * Verify that the object is actually a proxy instance.

         */

        if (!isProxyClass(proxy.getClass())) {

            throw new IllegalArgumentException("not a proxy instance");

        }

        final Proxy p = (Proxy) proxy;

        final InvocationHandler ih = p.h;

        if (System.getSecurityManager() != null) {

            Class<?> ihClass = ih.getClass();

            Class<?> caller = Reflection.getCallerClass();

            if (ReflectUtil.needsPackageAccessCheck(caller.getClassLoader(),

                                                    ihClass.getClassLoader()))

            {

                ReflectUtil.checkPackageAccess(ihClass);

            }

        }

        return ih;

    }

    private static final String PROXY_PACKAGE_PREFIX = ReflectUtil.PROXY_PACKAGE;

    /**

     * A cache of Method -> MethodHandle for default methods.

     */

    private static final ClassValue<ConcurrentHashMap<Method, MethodHandle>>

            DEFAULT_METHODS_MAP = new ClassValue<>() {

        @Override

        protected ConcurrentHashMap<Method, MethodHandle> computeValue(Class<?> type) {

            return new ConcurrentHashMap<>(4);

        }

    };

    private static ConcurrentHashMap<Method, MethodHandle> defaultMethodMap(Class<?> proxyClass) {

        assert isProxyClass(proxyClass);

        return DEFAULT_METHODS_MAP.get(proxyClass);

    }

    static final Object[] EMPTY_ARGS = new Object[0];

    static MethodHandle defaultMethodHandle(Class<? extends Proxy> proxyClass, Method method) {

        // lookup the cached method handle

        ConcurrentHashMap<Method, MethodHandle> methods = defaultMethodMap(proxyClass);

        MethodHandle superMH = methods.get(method);

        if (superMH == null) {

            MethodType type = methodType(method.getReturnType(), method.getParameterTypes());

            MethodHandles.Lookup lookup = MethodHandles.lookup();

            Class<?> proxyInterface = findProxyInterfaceOrElseThrow(proxyClass, method);

            MethodHandle dmh;

            try {

                dmh = proxyClassLookup(lookup, proxyClass)

                        .findSpecial(proxyInterface, method.getName(), type, proxyClass)

                        .withVarargs(false);

            } catch (IllegalAccessException | NoSuchMethodException e) {

                // should not reach here

                throw new InternalError(e);

            }

            // this check can be turned into assertion as it is guaranteed to succeed by the virtue of

            // looking up a default (instance) method declared or inherited by proxyInterface

            // while proxyClass implements (is a subtype of) proxyInterface ...

            assert ((BooleanSupplier) () -> {

                try {

                    // make sure that the method type matches

                    dmh.asType(type.insertParameterTypes(0, proxyClass));

                    return true;

                } catch (WrongMethodTypeException e) {

                    return false;

                }

            }).getAsBoolean() : "Wrong method type";

            // change return type to Object

            MethodHandle mh = dmh.asType(dmh.type().changeReturnType(Object.class));

            // wrap any exception thrown with InvocationTargetException

            mh = MethodHandles.catchException(mh, Throwable.class, InvocationException.wrapMH());

            // spread array of arguments among parameters (skipping 1st parameter - target)

            mh = mh.asSpreader(1, Object[].class, type.parameterCount());

            // change target type to Object

            mh = mh.asType(MethodType.methodType(Object.class, Object.class, Object[].class));

            // push MH into cache

            MethodHandle cached = methods.putIfAbsent(method, mh);

            if (cached != null) {

                superMH = cached;

            } else {

                superMH = mh;

            }

        }

        return superMH;

    }

    /**

     * Finds the first proxy interface that declares the given method

     * directly or indirectly.

     *