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Java动态代理可以通过以下几种方式实现：
- 使用
java.lang.reflect.Proxy类：Proxy类提供了一个静态方法newProxyInstance()，可以通过传入目标对象的类加载器、目标对象实现的接口和InvocationHandler接口的实现类来创建代理对象。InvocationHandler接口的实现类负责处理代理对象的方法调用。代理对象在调用方法时，会把方法调用转发给InvocationHandler的invoke()方法，从而实现代理功能。
public interface Subject { void doSomething(); } public class RealSubject implements Subject { public void doSomething() { System.out.println("RealSubject doSomething"); } } public class MyInvocationHandler implements InvocationHandler { private Subject target; public MyInvocationHandler(Subject target) { this.target = target; } public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { System.out.println("Before method invoke"); Object result = method.invoke(target, args); System.out.println("After method invoke"); return result; } } public class Main { public static void main(String[] args) { Subject realSubject = new RealSubject(); Subject proxySubject = (Subject) Proxy.newProxyInstance(realSubject.getClass().getClassLoader(), realSubject.getClass().getInterfaces(), new MyInvocationHandler(realSubject)); proxySubject.doSomething(); } } - 使用
CGLib库：CGLib是一个基于ASM框架的字节码生成库，它可以在运行时动态生成目标对象的子类，并覆盖其中的方法以实现代理功能。
public interface Subject { void doSomething(); } public class RealSubject implements Subject { public void doSomething() { System.out.println("RealSubject doSomething"); } } public class MyMethodInterceptor implements MethodInterceptor { public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable { System.out.println("Before method invoke"); Object result = proxy.invokeSuper(obj, args); System.out.println("After method invoke"); return result; } } public class Main { public static void main(String[] args) { Enhancer enhancer = new Enhancer(); enhancer.setSuperclass(RealSubject.class); enhancer.setCallback(new MyMethodInterceptor()); Subject proxySubject = (Subject) enhancer.create(); proxySubject.doSomething(); } } 需要注意的是，使用CGLib实现动态代理时，目标对象不能是final类或者包含final方法，因为CGLib是通过生成目标对象的子类来实现代理的。
- 使用
ByteBuddy库：ByteBuddy是一个轻量级的字节码操作库，它可以在运行时动态生成目标对象的子类，并覆盖其中的方法以实现代理功能。
public interface Subject { void doSomething(); } public class RealSubject implements Subject { public void doSomething() { System.out.println("RealSubject doSomething"); } } public class MyInterceptor implements MethodInterceptor { public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable { System.out.println("Before method invoke"); Object result = proxy.invokeSuper(obj, args); System.out.println("After method invoke"); return result; } } public class Main { public static void main(String[] args) throws Exception { Class<? extends Subject> proxyClass = new ByteBuddy() .subclass(Subject.class) .method(any()).intercept(MethodDelegation.to(MyInterceptor.class)) .make() .load(RealSubject.class.getClassLoader()) .getLoaded(); Subject proxySubject = proxyClass.getDeclaredConstructor().newInstance(); proxySubject.doSomething(); } } 需要注意的是，使用ByteBuddy实现动态代理时，需要引入net.bytebuddy:byte-buddy和net.bytebuddy:byte-buddy-agent两个依赖。
