no.sesat.commons.reflect

Class ConcurrentProxy

java.lang.Object

no.sesat.commons.reflect.ConcurrentProxy

public final class ConcurrentProxy
extends Object

java.lang.reflect.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. This class provides faster concurrent caching of Proxies through ConcurrentHashMaps, It delegates back to java.lang.reflect.Proxy for the construction of new Proxies and the required synchronisation surrounding it.

Version:

$Id$

Author:

@author Mck Semb Wever

See Also:

Proxy

Method Summary

Methods

Modifier and Type	Method and Description
static Class<?>	getProxyClass(ClassLoader loader, Class<?>... interfaces) Returns the java.lang.Class object for a proxy class given a class loader and an array of interfaces.
static Object	newProxyInstance(ClassLoader loader, Class<?>[] interfaces, InvocationHandler h) Returns an instance of a proxy class for the specified interfaces that dispatches method invocations to the specified invocation handler.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

getProxyClass

public static Class<?> getProxyClass(ClassLoader loader,
                     Class<?>... interfaces)
                              throws IllegalArgumentException

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.

Parameters:

loader - the class loader to define the proxy class

interfaces - the list of interfaces for the proxy class to implement

Returns:

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 getProxyClass are violated

NullPointerException - if the interfaces array argument or any of its elements are null

newProxyInstance

public static Object newProxyInstance(ClassLoader loader,
                      Class<?>[] interfaces,
                      InvocationHandler h)
                               throws IllegalArgumentException

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.

Parameters:

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

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

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