/*
* Copyright (c) 1999, 2012, 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.ref.Reference;
import java.lang.ref.WeakReference;
import java.security.AccessController;
import java.security.Permission;
import java.security.PrivilegedAction;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import java.util.List;
import java.util.WeakHashMap;
import sun.misc.ProxyGenerator;
import sun.reflect.CallerSensitive;
import sun.reflect.Reflection;
import sun.reflect.misc.ReflectUtil;
import sun.security.util.SecurityConstants;
Proxy
provides static methods for creating dynamic proxy classes and instances, and it is also the superclass of all dynamic proxy classes created by those methods. To create a proxy for some interface Foo
:
InvocationHandler handler = new MyInvocationHandler(...);
Class proxyClass = Proxy.getProxyClass(
Foo.class.getClassLoader(), new Class[] { Foo.class });
Foo f = (Foo) proxyClass.
getConstructor(new Class[] { InvocationHandler.class }).
newInstance(new Object[] { handler });
or more simply:
Foo f = (Foo) Proxy.newProxyInstance(Foo.class.getClassLoader(),
new Class[] { Foo.class },
handler);
A dynamic proxy class (simply referred to as a proxy
class below) is a class that implements a list of interfaces
specified at runtime when the class is created, with behavior as
described below.
A proxy interface is such an interface that is implemented
by a proxy class.
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:
- Proxy classes are public, final, and not abstract.
- 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. - A proxy class extends
java.lang.reflect.Proxy
. - A proxy class implements exactly the interfaces specified at its
creation, in the same order.
- If a proxy class implements a non-public interface, then it will
be defined in the same package as that interface. Otherwise, the
package of a proxy class is also unspecified. Note that package
sealing will not prevent a proxy class from being successfully defined
in a particular package at runtime, and neither will classes already
defined by the same class loader and the same package with particular
signers.
- Since a proxy class implements all of the interfaces specified at its creation, 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
Proxy.isProxyClass
method will return true if it is passed a proxy class-- a class returned by Proxy.getProxyClass
or the class of an object returned by Proxy.newProxyInstance
-- and false otherwise. - The
java.security.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
. - Each proxy class has one public constructor that takes one argument, an implementation of the interface
InvocationHandler
, to set the invocation handler for a proxy instance. Rather than having to use the reflection API to access the public constructor, a proxy instance can be also be created by calling the
Proxy.newProxyInstance
method, which combines the actions of calling Proxy.getProxyClass
with invoking the constructor with an invocation handler.
A proxy instance has the following properties:
- Given a proxy instance
proxy
and one of the interfaces implemented by its proxy class Foo
, 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
.
Methods Duplicated in Multiple Proxy Interfaces
When two or more interfaces of a proxy class 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: Since: 1.3
/**
* {@code Proxy} provides static methods for creating dynamic proxy
* classes and instances, and it is also the superclass of all
* dynamic proxy classes created by those methods.
*
* <p>To create a proxy for some interface {@code Foo}:
* <pre>
* InvocationHandler handler = new MyInvocationHandler(...);
* Class proxyClass = Proxy.getProxyClass(
* Foo.class.getClassLoader(), new Class[] { Foo.class });
* Foo f = (Foo) proxyClass.
* getConstructor(new Class[] { InvocationHandler.class }).
* newInstance(new Object[] { handler });
* </pre>
* or more simply:
* <pre>
* Foo f = (Foo) Proxy.newProxyInstance(Foo.class.getClassLoader(),
* new Class[] { Foo.class },
* handler);
* </pre>
*
* <p>A <i>dynamic proxy class</i> (simply referred to as a <i>proxy
* class</i> below) is a class that implements a list of interfaces
* specified at runtime when the class is created, with behavior as
* described below.
*
* A <i>proxy interface</i> is such an interface that is implemented
* by a proxy class.
*
* A <i>proxy instance</i> 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>Proxy classes are public, final, and not abstract.
*
* <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>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.
*
* <li>If a proxy class implements a non-public interface, then it will
* be defined in the same package as that interface. Otherwise, the
* package of a proxy class is also unspecified. Note that package
* sealing will not prevent a proxy class from being successfully defined
* in a particular package at runtime, and neither will classes already
* defined by the same class loader and the same package with particular
* signers.
*
* <li>Since a proxy class implements all of the interfaces specified at
* its creation, invoking {@code getInterfaces} on its
* {@code Class} object will return an array containing the same
* list of interfaces (in the order specified at its creation), invoking
* {@code 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 Proxy#isProxyClass Proxy.isProxyClass} method will
* return true if it is passed a proxy class-- a class returned by
* {@code Proxy.getProxyClass} or the class of an object returned by
* {@code Proxy.newProxyInstance}-- and false otherwise.
*
* <li>The {@code 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>Each proxy class has one public constructor that takes one argument,
* an implementation of the interface {@link InvocationHandler}, to set
* the invocation handler for a proxy instance. Rather than having to use
* the reflection API to access the public constructor, a proxy instance
* can be also be created by calling the {@link Proxy#newProxyInstance
* Proxy.newProxyInstance} method, which combines the actions of calling
* {@link Proxy#getProxyClass Proxy.getProxyClass} with invoking the
* constructor with an invocation handler.
* </ul>
*
* <p>A proxy instance has the following properties:
*
* <ul>
* <li>Given a proxy instance {@code proxy} and one of the
* interfaces implemented by its proxy class {@code Foo}, 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>Methods Duplicated in Multiple Proxy Interfaces</h3>
*
* <p>When two or more interfaces of a proxy class 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
*/
public class Proxy implements java.io.Serializable {
private static final long serialVersionUID = -2222568056686623797L;
prefix for all proxy class names /** prefix for all proxy class names */
private final static String proxyClassNamePrefix = "$Proxy";
parameter types of a proxy class constructor /** parameter types of a proxy class constructor */
private final static Class[] constructorParams =
{ InvocationHandler.class };
maps a class loader to the proxy class cache for that loader /** maps a class loader to the proxy class cache for that loader */
private static Map<ClassLoader, Map<List<String>, Object>> loaderToCache
= new WeakHashMap<ClassLoader, Map<List<String>, Object>>();
marks that a particular proxy class is currently being generated /** marks that a particular proxy class is currently being generated */
private static Object pendingGenerationMarker = new Object();
next number to use for generation of unique proxy class names /** next number to use for generation of unique proxy class names */
private static long nextUniqueNumber = 0;
private static Object nextUniqueNumberLock = new Object();
set of all generated proxy classes, for isProxyClass implementation /** set of all generated proxy classes, for isProxyClass implementation */
private static Map<Class<?>, Void> proxyClasses =
Collections.synchronizedMap(new WeakHashMap<Class<?>, Void>());
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
/**
* 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
*/
protected Proxy(InvocationHandler h) {
doNewInstanceCheck();
this.h = h;
}
private static class ProxyAccessHelper {
// The permission is implementation specific.
static final Permission PROXY_PERMISSION =
new ReflectPermission("proxyConstructorNewInstance");
// These system properties are defined to provide a short-term
// workaround if customers need to disable the new security checks.
static final boolean allowNewInstance;
static final boolean allowNullLoader;
static {
allowNewInstance = getBooleanProperty("sun.reflect.proxy.allowsNewInstance");
allowNullLoader = getBooleanProperty("sun.reflect.proxy.allowsNullLoader");
}
private static boolean getBooleanProperty(final String key) {
String s = AccessController.doPrivileged(new PrivilegedAction<String>() {
public String run() {
return System.getProperty(key);
}
});
return Boolean.valueOf(s);
}
static boolean needsNewInstanceCheck(Class<?> proxyClass) {
if (!Proxy.isProxyClass(proxyClass) || allowNewInstance) {
return false;
}
if (ReflectUtil.isNonPublicProxyClass(proxyClass)) {
for (Class<?> intf : proxyClass.getInterfaces()) {
if (!Modifier.isPublic(intf.getModifiers())) {
return true;
}
}
}
return false;
}
}
/*
* Access check on a proxy class that implements any non-public interface.
*
* @throws SecurityException if a security manager exists, and
* the caller does not have the permission.
*/
private void doNewInstanceCheck() {
SecurityManager sm = System.getSecurityManager();
Class<?> proxyClass = this.getClass();
if (sm != null && ProxyAccessHelper.needsNewInstanceCheck(proxyClass)) {
try {
sm.checkPermission(ProxyAccessHelper.PROXY_PERMISSION);
} catch (SecurityException e) {
throw new SecurityException("Not allowed to construct a Proxy "
+ "instance that implements a non-public interface", e);
}
}
}
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 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. There are several restrictions on the parameters that may be passed to Proxy.getProxyClass
:
- All of the
Class
objects in the 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 non-public interfaces must be in the same package;
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.
If any of these restrictions are violated, Proxy.getProxyClass
will throw an IllegalArgumentException
. If the interfaces
array argument or any of its elements are null
, a NullPointerException
will be thrown.
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
Throws: - IllegalArgumentException – if any of the restrictions on the parameters that may be passed to
getProxyClass
are violated - NullPointerException – if the
interfaces
array argument or any of its elements are null
Returns: a proxy class that is defined in the specified class loader
and that implements the specified interfaces
/**
* 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 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.
*
* <p>There are several restrictions on the parameters that may be
* passed to {@code Proxy.getProxyClass}:
*
* <ul>
* <li>All of the {@code Class} objects in the
* {@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:
* <pre>
* Class.forName(i.getName(), false, cl) == i
* </pre>
*
* <li>All non-public interfaces must be in the same package;
* 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>If any of these restrictions are violated,
* {@code Proxy.getProxyClass} will throw an
* {@code IllegalArgumentException}. If the {@code interfaces}
* array argument or any of its elements are {@code null}, a
* {@code NullPointerException} will be thrown.
*
* <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
* @return a proxy class that is defined in the specified class loader
* and that implements the specified interfaces
* @throws IllegalArgumentException if any of the restrictions on the
* parameters that may be passed to {@code getProxyClass}
* are violated
* @throws NullPointerException if the {@code interfaces} array
* argument or any of its elements are {@code null}
*/
@CallerSensitive
public static Class<?> getProxyClass(ClassLoader loader,
Class<?>... interfaces)
throws IllegalArgumentException
{
final Class<?>[] intfs = interfaces.clone();
final SecurityManager sm = System.getSecurityManager();
if (sm != null) {
checkProxyAccess(Reflection.getCallerClass(), loader, intfs);
}
return getProxyClass0(loader, intfs);
}
/*
* 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 via the defineClass0 method.
*/
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) {
if (!ProxyAccessHelper.allowNullLoader) {
sm.checkPermission(SecurityConstants.GET_CLASSLOADER_PERMISSION);
}
}
ReflectUtil.checkProxyPackageAccess(ccl, interfaces);
}
}
Generate a proxy class. Must call the checkProxyAccess method
to perform permission checks before calling this.
/**
* Generate a proxy class. Must call the checkProxyAccess method
* to perform permission checks before calling this.
*/
private static Class<?> getProxyClass0(ClassLoader loader,
Class<?>... interfaces) {
if (interfaces.length > 65535) {
throw new IllegalArgumentException("interface limit exceeded");
}
Class proxyClass = null;
/* collect interface names to use as key for proxy class cache */
String[] interfaceNames = new String[interfaces.length];
// for detecting duplicates
Set<Class<?>> interfaceSet = new HashSet<Class<?>>();
for (int i = 0; i < interfaces.length; i++) {
/*
* Verify that the class loader resolves the name of this
* interface to the same Class object.
*/
String interfaceName = interfaces[i].getName();
Class interfaceClass = null;
try {
interfaceClass = Class.forName(interfaceName, false, loader);
} catch (ClassNotFoundException e) {
}
if (interfaceClass != interfaces[i]) {
throw new IllegalArgumentException(
interfaces[i] + " is not visible from class loader");
}
/*
* Verify that the Class object actually represents an
* interface.
*/
if (!interfaceClass.isInterface()) {
throw new IllegalArgumentException(
interfaceClass.getName() + " is not an interface");
}
/*
* Verify that this interface is not a duplicate.
*/
if (interfaceSet.contains(interfaceClass)) {
throw new IllegalArgumentException(
"repeated interface: " + interfaceClass.getName());
}
interfaceSet.add(interfaceClass);
interfaceNames[i] = interfaceName;
}
/*
* Using string representations of the proxy interfaces as
* keys in the proxy class cache (instead of their Class
* objects) is sufficient because we require the proxy
* interfaces to be resolvable by name through the supplied
* class loader, and it has the advantage that using a string
* representation of a class makes for an implicit weak
* reference to the class.
*/
List<String> key = Arrays.asList(interfaceNames);
/*
* Find or create the proxy class cache for the class loader.
*/
Map<List<String>, Object> cache;
synchronized (loaderToCache) {
cache = loaderToCache.get(loader);
if (cache == null) {
cache = new HashMap<List<String>, Object>();
loaderToCache.put(loader, cache);
}
/*
* This mapping will remain valid for the duration of this
* method, without further synchronization, because the mapping
* will only be removed if the class loader becomes unreachable.
*/
}
/*
* Look up the list of interfaces in the proxy class cache using
* the key. This lookup will result in one of three possible
* kinds of values:
* null, if there is currently no proxy class for the list of
* interfaces in the class loader,
* the pendingGenerationMarker object, if a proxy class for the
* list of interfaces is currently being generated,
* or a weak reference to a Class object, if a proxy class for
* the list of interfaces has already been generated.
*/
synchronized (cache) {
/*
* Note that we need not worry about reaping the cache for
* entries with cleared weak references because if a proxy class
* has been garbage collected, its class loader will have been
* garbage collected as well, so the entire cache will be reaped
* from the loaderToCache map.
*/
do {
Object value = cache.get(key);
if (value instanceof Reference) {
proxyClass = (Class<?>) ((Reference) value).get();
}
if (proxyClass != null) {
// proxy class already generated: return it
return proxyClass;
} else if (value == pendingGenerationMarker) {
// proxy class being generated: wait for it
try {
cache.wait();
} catch (InterruptedException e) {
/*
* The class generation that we are waiting for should
* take a small, bounded time, so we can safely ignore
* thread interrupts here.
*/
}
continue;
} else {
/*
* No proxy class for this list of interfaces has been
* generated or is being generated, so we will go and
* generate it now. Mark it as pending generation.
*/
cache.put(key, pendingGenerationMarker);
break;
}
} while (true);
}
try {
String proxyPkg = null; // package to define proxy class in
/*
* 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 (int i = 0; i < interfaces.length; i++) {
int flags = interfaces[i].getModifiers();
if (!Modifier.isPublic(flags)) {
String name = interfaces[i].getName();
int n = name.lastIndexOf('.');
String pkg = ((n == -1) ? "" : name.substring(0, n + 1));
if (proxyPkg == null) {
proxyPkg = pkg;
} else if (!pkg.equals(proxyPkg)) {
throw new IllegalArgumentException(
"non-public interfaces from different packages");
}
}
}
if (proxyPkg == null) {
// if no non-public proxy interfaces, use com.sun.proxy package
proxyPkg = ReflectUtil.PROXY_PACKAGE + ".";
}
{
/*
* Choose a name for the proxy class to generate.
*/
long num;
synchronized (nextUniqueNumberLock) {
num = nextUniqueNumber++;
}
String proxyName = proxyPkg + proxyClassNamePrefix + num;
/*
* Verify that the class loader hasn't already
* defined a class with the chosen name.
*/
/*
* Generate the specified proxy class.
*/
byte[] proxyClassFile = ProxyGenerator.generateProxyClass(
proxyName, interfaces);
try {
proxyClass = defineClass0(loader, proxyName,
proxyClassFile, 0, proxyClassFile.length);
} 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());
}
}
// add to set of all generated proxy classes, for isProxyClass
proxyClasses.put(proxyClass, null);
} finally {
/*
* We must clean up the "pending generation" state of the proxy
* class cache entry somehow. If a proxy class was successfully
* generated, store it in the cache (with a weak reference);
* otherwise, remove the reserved entry. In all cases, notify
* all waiters on reserved entries in this cache.
*/
synchronized (cache) {
if (proxyClass != null) {
cache.put(key, new WeakReference<Class<?>>(proxyClass));
} else {
cache.remove(key);
}
cache.notifyAll();
}
}
return proxyClass;
}
Returns an instance of a proxy class for the specified interfaces
that dispatches method invocations to the specified invocation
handler. This method is equivalent to:
Proxy.getProxyClass(loader, interfaces).
getConstructor(new Class[] { InvocationHandler.class }).
newInstance(new Object[] { handler });
Proxy.newProxyInstance
throws IllegalArgumentException
for the same reasons that Proxy.getProxyClass
does.
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 that may be passed to
getProxyClass
are violated - NullPointerException – if the
interfaces
array argument or any of its elements are null
, or if the invocation handler, h
, is null
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
/**
* Returns an instance of a proxy class for the specified interfaces
* that dispatches method invocations to the specified invocation
* handler. This method is equivalent to:
* <pre>
* Proxy.getProxyClass(loader, interfaces).
* getConstructor(new Class[] { InvocationHandler.class }).
* newInstance(new Object[] { handler });
* </pre>
*
* <p>{@code Proxy.newProxyInstance} throws
* {@code IllegalArgumentException} for the same reasons that
* {@code Proxy.getProxyClass} does.
*
* @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 restrictions on the
* parameters that may be passed to {@code getProxyClass}
* are violated
* @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}
*/
@CallerSensitive
public static Object newProxyInstance(ClassLoader loader,
Class<?>[] interfaces,
InvocationHandler h)
throws IllegalArgumentException
{
if (h == null) {
throw new NullPointerException();
}
final Class<?>[] intfs = interfaces.clone();
final SecurityManager sm = System.getSecurityManager();
if (sm != null) {
checkProxyAccess(Reflection.getCallerClass(), loader, intfs);
}
/*
* Look up or generate the designated proxy class.
*/
Class<?> cl = getProxyClass0(loader, intfs);
/*
* Invoke its constructor with the designated invocation handler.
*/
try {
final Constructor<?> cons = cl.getConstructor(constructorParams);
final InvocationHandler ih = h;
if (sm != null && ProxyAccessHelper.needsNewInstanceCheck(cl)) {
// create proxy instance with doPrivilege as the proxy class may
// implement non-public interfaces that requires a special permission
return AccessController.doPrivileged(new PrivilegedAction<Object>() {
public Object run() {
return newInstance(cons, ih);
}
});
} else {
return newInstance(cons, ih);
}
} catch (NoSuchMethodException e) {
throw new InternalError(e.toString());
}
}
private static Object newInstance(Constructor<?> cons, InvocationHandler h) {
try {
return cons.newInstance(new Object[] {h} );
} catch (IllegalAccessException e) {
throw new InternalError(e.toString());
} catch (InstantiationException e) {
throw new InternalError(e.toString());
} catch (InvocationTargetException e) {
Throwable t = e.getCause();
if (t instanceof RuntimeException) {
throw (RuntimeException) t;
} else {
throw new InternalError(t.toString());
}
}
}
Returns true if and only if the specified class was dynamically generated to be a proxy class using the getProxyClass
method or the newProxyInstance
method. 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
.
Params: - cl – the class to test
Throws: - NullPointerException – if
cl
is null
Returns: true
if the class is a proxy class and false
otherwise
/**
* Returns true if and only if the specified class was dynamically
* generated to be a proxy class using the {@code getProxyClass}
* method or the {@code newProxyInstance} method.
*
* <p>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}
*/
public static boolean isProxyClass(Class<?> cl) {
if (cl == null) {
throw new NullPointerException();
}
return proxyClasses.containsKey(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
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
*/
@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 native Class defineClass0(ClassLoader loader, String name,
byte[] b, int off, int len);
}