Dynamic Proxy Classes

Dynamic proxy classes : A dynamic proxy class is a class that implements a list of interfaces specified at runtime such that a method invocation through one of the interfaces on an instance of the class will be encoded and dispatched to another object through a uniform interface



Example:-

public interface Foo {
Object bar(Object obj) throws BazException;
}

public class FooImpl implements Foo {
Object bar(Object obj) throws BazException {
// ...
}
}

public class DebugProxy implements java.lang.reflect.InvocationHandler {

private Object obj;

public static Object newInstance(Object obj) {
return java.lang.reflect.Proxy.newProxyInstance(
obj.getClass().getClassLoader(),
obj.getClass().getInterfaces(),
new DebugProxy(obj));
}

private DebugProxy(Object obj) {
this.obj = obj;
}

public Object invoke(Object proxy, Method m, Object[] args)
throws Throwable
{
Object result;
try {
System.out.println("before method " + m.getName());
result = m.invoke(obj, args);
} catch (InvocationTargetException e) {
throw e.getTargetException();
} catch (Exception e) {
throw new RuntimeException("unexpected invocation exception: " +
e.getMessage());
} finally {
System.out.println("after method " + m.getName());
}
return result;
}
}