java.lang.reflect.Proxy Class in Java
Last Updated :
20 Jul, 2022
A proxy class is present in java.lang package. A proxy class has certain methods which are used for creating dynamic proxy classes and instances, and all the classes created by those methods act as subclasses for this proxy class.
Class declaration:
public class Proxy
extends Object
implements Serializable
Fields:
protected InvocationHandler h
It handles the invocation for this proxy instance.
Constructor:
protected Proxy(InvocationHandler h)
Constructs a Proxy instance from a subclass which is typically a dynamic proxy class. The instance is automatically created with the required value of this invocation handler h.
Creating Invocation Handler:
Java
import java.lang.reflect.InvocationHandler;
class demoInvocationHandler implements InvocationHandler {
@Override
public Object invoke(Object proxy, Method method,
Object[] args) throws Throwable
{
return null;
}
}
public class GFG {
public static void main(String[] args)
{
InvocationHandler h = new demoInvocationHandler();
}
}
|
Methods
| Method |
Description |
| getInvocationHandler(Object proxy) |
This method returns the invocation handler for the specified proxy instance. |
| getProxyClass(ClassLoader loader, Class<?>… interfaces) |
This method returns the java.lang.Class object for a proxy class given a class loader and an array of interfaces. |
| isProxyClass(Class<?> cl) |
This method 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. |
| newProxyInstance(ClassLoader loader, Class<?>[] interfaces, InvocationHandler h) |
This method returns an instance of a proxy class for the specified interfaces that dispatches method invocations to the specified invocation handler. |
1. static InvocationHandler getInvocationHandler(Object proxy):
Returns the invocation handler for this proxy instance.
Java
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.List;
class demoInvocationHandler implements InvocationHandler {
@Override
public Object invoke(Object proxy, Method method,
Object[] args) throws Throwable
{
return null;
}
}
interface demoInterface {
}
public class GFG {
public static void main(String[] args)
{
InvocationHandler h = new demoInvocationHandler();
List proxyClass = (List)Proxy.newProxyInstance(
GFG.class.getClassLoader(),
new Class[] { List.class },
new demoInvocationHandler());
System.out.println(
Proxy.getInvocationHandler(proxyClass));
}
}
|
Output
demoInvocationHandler@378fd1ac
2. static Class<?> getProxyClass(ClassLoader loader, Class<?>… interfaces):
Returns the java.lang.Class object for a proxy class. The proxy class are going to be defined by the required class loader and can implement all the supplied interfaces.
Java
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.List;
class demoInvocationHandler implements InvocationHandler {
@Override
public Object invoke(Object proxy, Method method,
Object[] args) throws Throwable
{
return null;
}
}
interface demoInterface {
}
class demo {
}
public class GFG {
public static void main(String[] args)
{
InvocationHandler h = new demoInvocationHandler();
@SuppressWarnings("deprecation")
Class<?> proxyClass = (Class<?>)Proxy.getProxyClass(
demo.class.getClassLoader(),
new Class[] { demoInterface.class });
System.out.println("Program executed successfully");
}
}
|
Output
Program executed successfully
3. static boolean isProxyClass(Class<?> cl):
Returns true if this class was dynamically generated to be a proxy class using the getProxyClass method or the newProxyInstance method else returns false.
Java
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.List;
class demoInvocationHandler implements InvocationHandler {
@Override
public Object invoke(Object proxy, Method method,
Object[] args) throws Throwable
{
return null;
}
}
interface demoInterface {
}
class demo {
}
public class GFG {
public static void main(String[] args)
{
InvocationHandler h = new demoInvocationHandler();
@SuppressWarnings("deprecation")
Class<?> proxyClass = (Class<?>)Proxy.getProxyClass(
demo.class.getClassLoader(),
new Class[] { demoInterface.class });
System.out.println(Proxy.isProxyClass(proxyClass));
}
}
|
4. static Object newProxyInstance(ClassLoader loader, Class<?>[] interfaces, InvocationHandler h):
Returns a proxy object of a proxy class which is defined by the class loader. It implements all the required interfaces.
Java
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.List;
class demoInvocationHandler implements InvocationHandler {
@Override
public Object invoke(Object proxy, Method method,
Object[] args) throws Throwable
{
return null;
}
}
interface demoInterface {
}
public class GFG {
public static void main(String[] args)
{
InvocationHandler h = new demoInvocationHandler();
List proxyClass = (List)Proxy.newProxyInstance(
GFG.class.getClassLoader(),
new Class[] { List.class },
new demoInvocationHandler());
System.out.println(
"Proxy object returned successfully");
}
}
|
Output
Proxy object returned successfully
Proxy class inherits all the methods of java.lang.Object class.