4 Proxy - Reflect

Enhancer enhancer = new Enhancer(); enhancer.setSuperclass(RealUserService.class); enhancer.setCallback(new MethodInterceptor() public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable // interceptor logic return proxy.invokeSuper(obj, args); ); RealUserService proxy = (RealUserService) enhancer.create(); The reflect 4 proxy mechanism remains a cornerstone of Java’s dynamic capabilities. Although newer versions of Java introduced features like dynamic proxies via MethodHandles (more lightweight) and inline classes (Project Valhalla), java.lang.reflect.Proxy is still widely used because it is simple, standardized, and deeply integrated into major frameworks.

UserService proxy = (UserService) Proxy.newProxyInstance( UserService.class.getClassLoader(), new Class[]UserService.class, new LoggingHandler(realService) ); // Call methods via proxy String name = proxy.getUserName(42); proxy.updateUser(42, "John Doe"); reflect 4 proxy

| Feature | JDK Proxy | CGLIB | Byte Buddy | |---------|-----------|-------|-------------| | | Interfaces only | Concrete classes | Both | | Implementation | Reflection | Subclassing (bytecode) | Bytecode generation | | Performance | Medium | High | Highest | | Complexity | Low | Medium | High | | Modern use | Spring AOP (default) | Spring (fallback) | Mocking frameworks | Enhancer enhancer = new Enhancer(); enhancer