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

Proxy
https://openjdk.java.net/
GPLv2 + Classpath Exception
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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package java.lang.reflect;

import java.lang.module.ModuleDescriptor;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.Arrays;
import java.util.Collections;
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.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicLong;
import java.util.stream.Collectors;
import java.util.stream.Stream;

import jdk.internal.loader.BootLoader;
import jdk.internal.module.Modules;
import jdk.internal.misc.Unsafe;
import jdk.internal.misc.VM;
import jdk.internal.reflect.CallerSensitive;
import jdk.internal.reflect.Reflection;
import jdk.internal.loader.ClassLoaderValue;
import sun.reflect.misc.ReflectUtil;
import sun.security.action.GetPropertyAction;
import sun.security.util.SecurityConstants;

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


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 Foo: 
    InvocationHandler handler = new MyInvocationHandler(...);
    Foo f = (Foo) Proxy.newProxyInstance(Foo.class.getClassLoader(),
                                         new Class<?>[] { Foo.class },
                                         handler);


A proxy class is a class created at runtime that implements a specified
list of interfaces, known as proxy interfaces. A proxy instance
is an instance of a proxy class.
Each proxy instance has an associated invocation handler object, which implements the interface InvocationHandler. A method invocation on a proxy instance through one of its proxy interfaces will be dispatched to the 
invoke method of the instance's invocation handler, passing the proxy instance, a java.lang.reflect.Method object identifying the method that was invoked, and an array of type 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. 
A proxy class has the following properties:

The unqualified name of a proxy class is unspecified. The space of class names that begin with the string "$Proxy" should be, however, reserved for proxy classes. 
The package and module in which a proxy class is defined is specified
below.
A proxy class is final and non-abstract.
A proxy class extends java.lang.reflect.Proxy. 
A proxy class implements exactly the interfaces specified at its creation, in the same order. Invoking getInterfaces on its Class object will return an array containing the same list of interfaces (in the order specified at its creation), invoking getMethods on its Class object will return an array of Method objects that include all of the methods in those interfaces, and invoking getMethod will find methods in the proxy interfaces as would be expected. 
The ProtectionDomain of a proxy class is the same as that of system classes loaded by the bootstrap class loader, such as java.lang.Object, because the code for a proxy class is generated by trusted system code. This protection domain will typically be granted java.security.AllPermission. 
The Proxy.isProxyClass method can be used to determine if a given class is a proxy class. 
A proxy instance has the following properties:

Given a proxy instance proxy and one of the interfaces, Foo, implemented by its proxy class, the following expression will return true:  proxy instanceof Foo 
 and the following cast operation will succeed (rather than throwing a ClassCastException):  (Foo) proxy 
Each proxy instance has an associated invocation handler, the one that was passed to its constructor. The static Proxy.getInvocationHandler method will return the invocation handler associated with the proxy instance passed as its argument. 
An interface method invocation on a proxy instance will be encoded and dispatched to the invocation handler's invoke method as described in the documentation for that method. 
An invocation of the hashCode, equals, or toString methods declared in java.lang.Object on a proxy instance will be encoded and dispatched to the invocation handler's invoke method in the same manner as interface method invocations are encoded and dispatched, as described above. The declaring class of the Method object passed to invoke will be java.lang.Object. Other public methods of a proxy instance inherited from java.lang.Object are not overridden by a proxy class, so invocations of those methods behave like they do for instances of java.lang.Object. 
Package and Module Membership of Proxy Class
 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 getProxyClass(ClassLoader, Class<?>[]) or newProxyInstance(ClassLoader, Class<?>[], InvocationHandler) methods is specified as follows: 
If all the proxy interfaces are in exported or open
    packages:

if all the proxy interfaces are public, then the proxy class is
    public in a package exported by the unnamed module of the specified loader. The name of the package is unspecified.
if at least one of all the proxy interfaces is non-public, then
    the proxy class is non-public 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
    not possible.


If at least one proxy interface is in a package that is
    non-exported and non-open:

if all the proxy interfaces are public, then the proxy class is
    public in a non-exported, non-open package of
    dynamic module.
    The names of the package and the module are unspecified.
if at least one of all the proxy interfaces is non-public, then
    the proxy class is non-public 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
    not possible.




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.
 Note that it is possible for arbitrary code to obtain access to a proxy class in an open package with setAccessible, whereas a proxy class in a non-open package is never accessible to code outside the module of the proxy class. 

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.
Dynamic Modules
 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 Constructor.newInstance(Object...) on a proxy class in a dynamic module will throw IllegalAccessException; Proxy.newProxyInstance method should be used instead. 
 A dynamic module can read the modules of all of the superinterfaces of a proxy class and the modules of the types referenced by all public method signatures of a proxy class. If a superinterface or a referenced type, say T, is in a non-exported package, the module of T is updated to export the package of T to the dynamic module. 
Methods Duplicated in Multiple Proxy Interfaces
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 duplicate method is invoked on a proxy instance, the 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 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 invoke method, regardless of the reference type through which the method invocation occurred. 
If a proxy interface contains a method with the same name and parameter signature as the hashCode, equals, or toString methods of java.lang.Object, when such a method is invoked on a proxy instance, the Method object passed to the invocation handler will have java.lang.Object as its declaring class. In other words, the public, non-final methods of java.lang.Object logically precede all of the proxy interfaces for the determination of which Method object to pass to the invocation handler. 
Note also that when a duplicate method is dispatched to an invocation handler, the invoke method may only throw checked exception types that are assignable to one of the exception types in the throws clause of the method in all of the proxy interfaces that it can be invoked through. If the 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 UndeclaredThrowableException will be thrown by the invocation on the proxy instance. This restriction means that not all of the exception types returned by invoking getExceptionTypes on the Method object passed to the invoke method can necessarily be thrown successfully by the invoke method. 
Author:      Peter Jones
See Also: InvocationHandler
Since:       1.3
@revised 9
@spec JPMS/**
 *
 * {@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>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>
 *
 * <h3><a id="membership">Package and Module Membership of Proxy Class</a></h3>
 *
 * 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 a package exported by the
 *     {@linkplain ClassLoader#getUnnamedModule() unnamed module} of the specified
 *     loader. The name of the package is 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 types referenced by all public method signatures
 * of a proxy class.  If a superinterface or a referenced type, 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
 * @spec JPMS
 */
public class Proxy implements java.io.Serializable {
    private static final long serialVersionUID = -2222568056686623797L;

    parameter types of a proxy class constructor /** parameter types of a proxy class constructor */
    private static final Class<?>[] constructorParams =
        { InvocationHandler.class };

    a cache of proxy constructors with accessible flag already set /**
     * 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 /**
     * the invocation handler for this proxy instance.
     * @serial
     */
    protected InvocationHandler h;

    Prohibits instantiation.
/**
     * Prohibits instantiation.
     */
    private Proxy() {
    }

    Constructs a new Proxy instance from a subclass (typically, a dynamic proxy class) with the specified value for its invocation handler. 
Params: h – the invocation handler for this proxy instance
Throws: NullPointerException – if the given invocation handler, h, is null./**
     * 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 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. 
Params: loader – the class loader to define the proxy class
interfaces – the list of interfaces for the proxy class
         to implement
Throws: IllegalArgumentException – if any of the 
         restrictions on the parameters are violated
SecurityException – if a security manager, s, is present
         and any of the following conditions is met:
         
             the given loader is null and the caller's class loader is not null and the invocation of 
            s.checkPermission with RuntimePermission("getClassLoader") permission denies access.
             for each proxy interface, intf, the caller's class loader is not the same as or an ancestor of the class loader for intf and invocation of 
            s.checkPackageAccess() denies access to intf.
         
NullPointerException – if the interfaces array argument or any of its elements are null
See Also: Package and Module Membership of Proxy Class
Returns:  a proxy class that is defined in the specified class loader
         and that implements the specified interfaces
Deprecated: Proxy classes generated in a named module are encapsulated and not accessible to code outside its module. Constructor.newInstance will throw IllegalAccessException when it is called on an inaccessible proxy class. Use newProxyInstance(ClassLoader, Class<?>[], InvocationHandler) to create a proxy instance instead.
@revised 9
@spec JPMS/**
     * 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
     * @spec JPMS
     */
    @Deprecated
    @CallerSensitive
    public static Class<?> getProxyClass(ClassLoader loader,
                                         Class<?>... interfaces)
        throws IllegalArgumentException
    {
        Class<?> caller = System.getSecurityManager() == null
                              ? null
                              : Reflection.getCallerClass();

        return getProxyConstructor(caller, loader, interfaces)
            .getDeclaringClass();
    }

    Returns the Constructor object of a proxy class that takes a single argument of type InvocationHandler, given a class loader and an array of interfaces. The returned constructor will have the accessible flag already set. 
Params: caller – passed from a public-facing @CallerSensitive method if SecurityManager is set or null if there's no SecurityManager
loader – the class loader to define the proxy class
interfaces – the list of interfaces for the proxy class
         to implement
Returns:  a Constructor of the proxy class taking single InvocationHandler parameter/**
     * 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)
    {
        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.
/**
     * 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 Unsafe UNSAFE = Unsafe.getUnsafe();

        // 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;

            /*
             * 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");
                    }
                }
            }

            if (proxyPkg == null) {
                // all proxy interfaces are public
                proxyPkg = m.isNamed() ? PROXY_PACKAGE_PREFIX + "." + m.getName()
                                       : PROXY_PACKAGE_PREFIX;
            } 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(
                    proxyName, interfaces.toArray(EMPTY_CLASS_ARRAY), accessFlags);
            try {
                Class<?> pc = UNSAFE.defineClass(proxyName, proxyClassFile,
                                                 0, proxyClassFile.length,
                                                 loader, null);
                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 defineProxyClass(Module, List<Class<?>>) /**
         * 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.
/**
         * 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.
         */
        Constructor<?> build() {
            Class<?> proxyClass = defineProxyClass(module, interfaces);
            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 Proxy.newProxyInstance/**
         * 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 loader resolves the name of this
                 * interface to the same Class object.
                 */
                ensureVisible(loader, intf);

                /*
                 * Verify that the Class object actually represents an
                 * interface.
                 */
                if (!intf.isInterface()) {
                    throw new IllegalArgumentException(intf.getName() + " is not an interface");
                }

                /*
                 * 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 all proxy interfaces are public and in exported packages,
then the proxy class is in unnamed module.
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 at least one in a non-exported
package, then the proxy class is in a dynamic module in a
non-exported package.  Reads edge and qualified exports are added
for dynamic module to access.
/**
         * Returns the module that the generated proxy class belongs to.
         *
         * If all proxy interfaces are public and in exported packages,
         * then the proxy class is in unnamed module.
         *
         * 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 at least one in a non-exported
         * package, then the proxy class is in a dynamic module in a
         * non-exported package.  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> modulePrivateTypes = new HashMap<>();
            Map<Class<?>, Module> packagePrivateTypes = new HashMap<>();
            for (Class<?> intf : interfaces) {
                Module m = intf.getModule();
                if (Modifier.isPublic(intf.getModifiers())) {
                    // module-private types
                    if (!m.isExported(intf.getPackageName())) {
                        modulePrivateTypes.put(intf, m);
                    }
                } else {
                    packagePrivateTypes.put(intf, m);
                }
            }

            // all proxy interfaces are public and exported, the proxy class
            // is in unnamed module.  Such proxy class is accessible to
            // any unnamed module and named module that can read unnamed module
            if (packagePrivateTypes.isEmpty() && modulePrivateTypes.isEmpty()) {
                return loader != null ? loader.getUnnamedModule()
                                      : BootLoader.getUnnamedModule();
            }

            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)
                if (packagePrivateTypes.size() > 1 &&
                        (packagePrivateTypes.keySet().stream()  // more than one package
                                 .map(Class::getPackageName).distinct().count() > 1 ||
                         packagePrivateTypes.values().stream()  // or more than one module
                                 .distinct().count() > 1)) {
                    throw new IllegalArgumentException(
                            "non-public interfaces from different packages");
                }

                // all package-private types are in the same module (named or unnamed)
                Module target = null;
                for (Module m : packagePrivateTypes.values()) {
                    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");
                    }
                    target = m;
                }

                // validate if the target module can access all other interfaces
                for (Class<?> intf : interfaces) {
                    Module m = intf.getModule();
                    if (m == target) continue;

                    if (!target.canRead(m) || !m.isExported(intf.getPackageName(), target)) {
                        throw new IllegalArgumentException(target + " can't access " + intf.getName());
                    }
                }

                // return the module of the package-private interface
                return target;
            }

            // All proxy interfaces are public and at least one in a non-exported
            // package.  So maps to a dynamic proxy module and add reads edge
            // and qualified exports, if necessary
            Module target = 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(target, c);
            }
            return target;
        }

        /*
         * 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 for the generated proxy classes in
         * a non-exported package named com.sun.proxy.$MODULE.
         *
         * 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))
                                    .build();
                Module m = Modules.defineModule(ld, descriptor, null);
                Modules.addReads(m, Proxy.class.getModule());
                // java.base to create proxy instance
                Modules.addExports(m, pn, Object.class.getModule());
                return m;
            });
        }
    }

    Returns a proxy instance for the specified interfaces
that dispatches method invocations to the specified invocation
handler.

IllegalArgumentException will be thrown if any of the following restrictions is violated:

All of Class objects in the given interfaces array must represent interfaces, not classes or primitive types. 
No two elements in the interfaces array may refer to identical Class objects. 
All of the interface types must be visible by name through the specified class loader. In other words, for class loader cl and every interface i, the following expression must be true: Class.forName(i.getName(), false, cl) == i 
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.
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.
For any set of member methods of the specified interfaces
that have the same signature:

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.
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.

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 interfaces array must not exceed 65535. 
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.
Params: loader – the class loader to define the proxy class
interfaces – the list of interfaces for the proxy class
         to implement
h – the invocation handler to dispatch method invocations to
Throws: IllegalArgumentException – if any of the 
         restrictions on the parameters are violated
SecurityException – if a security manager, s, is present
         and any of the following conditions is met:
         
          the given loader is null and the caller's class loader is not null and the invocation of 
              s.checkPermission with RuntimePermission("getClassLoader") permission denies access;
          for each proxy interface, intf, the caller's class loader is not the same as or an ancestor of the class loader for intf and invocation of 
              s.checkPackageAccess() denies access to intf;
          any of the given proxy interfaces is non-public and the caller class is not in the same runtime package as the non-public interface and the invocation of s.checkPermission with ReflectPermission("newProxyInPackage.{package name}") permission denies access.
         
NullPointerException – if the interfaces array argument or any of its elements are null, or if the invocation handler, h, is null
See Also: Package and Module Membership of Proxy Class
Returns:  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
@revised 9
@spec JPMS/**
     * 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 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
     * @spec JPMS
     */
    @CallerSensitive
    public static Object newProxyInstance(ClassLoader loader,
                                          Class<?>[] interfaces,
                                          InvocationHandler h) {
        Objects.requireNonNull(h);

        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) {
        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.
/**
     * Returns the class loader for the given module.
     */
    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.
Params: cl – the class to test
Throws: NullPointerException – if cl is null
Implementation Note: 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 Proxy.
Returns:  true if the class is a proxy class and false otherwise
@revised 9
@spec JPMS/**
     * 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
     * @spec JPMS
     */
    public static boolean isProxyClass(Class<?> cl) {
        return Proxy.class.isAssignableFrom(cl) && ProxyBuilder.isProxyClass(cl);
    }

    Returns the invocation handler for the specified proxy instance.
Params: proxy – the proxy instance to return the invocation handler for
Throws: IllegalArgumentException – if the argument is not a
         proxy instance
SecurityException – if a security manager, s, 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 
         s.checkPackageAccess() denies access to the invocation handler's class.
Returns:  the invocation handler for the proxy instance/**
     * 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.
     */
    @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 Class<?>[] EMPTY_CLASS_ARRAY = new Class<?>[0];
    private static final String PROXY_PACKAGE_PREFIX = ReflectUtil.PROXY_PACKAGE;
}
Author:	Peter Jones
See Also:	InvocationHandler
Since:	1.3
@revised	9
@spec	JPMS
Params:	h – the invocation handler for this proxy instance
Throws:	NullPointerException – if the given invocation handler, `h`, is `null`.
Params:	loader – the class loader to define the proxy class interfaces – the list of interfaces for the proxy class to implement
Throws:	IllegalArgumentException – if any of the restrictions on the parameters are violated SecurityException – if a security manager, s, is present and any of the following conditions is met: the given `loader` is `null` and the caller's class loader is not `null` and the invocation of `s.checkPermission` with `RuntimePermission("getClassLoader")` permission denies access. for each proxy interface, `intf`, the caller's class loader is not the same as or an ancestor of the class loader for `intf` and invocation of `s.checkPackageAccess()` denies access to `intf`. NullPointerException – if the `interfaces` array argument or any of its elements are `null`
See Also:	Package and Module Membership of Proxy Class
Returns:	a proxy class that is defined in the specified class loader and that implements the specified interfaces
Deprecated:	Proxy classes generated in a named module are encapsulated and not accessible to code outside its module. `Constructor.newInstance` will throw `IllegalAccessException` when it is called on an inaccessible proxy class. Use `newProxyInstance(ClassLoader, Class<?>[], InvocationHandler)` to create a proxy instance instead.
@revised	9
@spec	JPMS
Params:	caller – passed from a public-facing @CallerSensitive method if SecurityManager is set or `null` if there's no SecurityManager loader – the class loader to define the proxy class interfaces – the list of interfaces for the proxy class to implement
Returns:	a Constructor of the proxy class taking single `InvocationHandler` parameter
Params:	cl – the class to test
Throws:	NullPointerException – if `cl` is `null`
Implementation Note:	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 `Proxy`.
Returns:	`true` if the class is a proxy class and `false` otherwise
@revised	9
@spec	JPMS
Params:	proxy – the proxy instance to return the invocation handler for
Throws:	IllegalArgumentException – if the argument is not a proxy instance SecurityException – if a security manager, s, 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 `s.checkPackageAccess()` denies access to the invocation handler's class.
Returns:	the invocation handler for the proxy instance
/

java/ 11/ java.base/java/lang/reflect/Proxy.java

Package and Module Membership of Proxy Class

Dynamic Modules

Methods Duplicated in Multiple Proxy Interfaces
