public interface Hello {
 void say(String msg);
}

public class HelloImpl implements Hello {
 public void say(String msg) {
  System.out.println("Hi,"+msg);
 }
}

public class HelloProxy implements Hello{
 private Hello hello;
 public HelloProxy(Hello hello){
  this.hello = hello;
 }
 public void say(String msg){
  before();
  hello.say(msg);
  after();
 }
 private void before(){
  System.out.println("Before");
 }
 private void after(){
  System.out.println("After");
 }
}

/**
 * @Author LZHL
 * @Create 2017-02-19 10:26
 * @Description
 */
public class Main {
 public static void main(String[] args) throws Exception {
  HelloImpl target = new HelloImpl();
  HelloProxy proxy = new HelloProxy(target);
  proxy.say("LZHL");
 }
}

public class HelloTarget {
 public void sayHello(String name){
  System.out.println("Hi,"+name);
 }
}

public class HelloProxy extends HelloTarget{
　　private HelloTarget target;
　　public HelloProxy(HelloTarget target){
　　　　this.target = target;
　　} 
　　@Override
 public void sayHello(String name) {
  this.before();
  target.sayHello(name);
  this.after();
 }
 private void before(){
  System.out.println("Before");
 }
 private void after(){
  System.out.println("After");
 }
}

public class Main {
 public static void main(String[] args) throws Exception {
  HelloTarget target = new HelloTarget(); 
　　　　HelloProxy proxy= new HelloProxy(target);
  proxy.sayHello("LZHL");
 }
}

/**
 * @Author LZHL
 * @Create 2017-02-19 12:46
 * @Description
 */
public class Main {
 public static void main(String[] args){
  final HelloImpl target = new HelloImpl();
  Object proxyInstance = Proxy.newProxyInstance(target.getClass().getClassLoader(), target.getClass().getInterfaces(), new InvocationHandler() {
   /*
    * proxy: 代理对象
    * method: 目标对象的方法对象
    * args: 目标对象方法的参数
    * return: 目标对象方法的返回值
    */
   public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
    System.out.println("before");
    Object retValue = method.invoke(target, args);
    System.out.println("after");
    return retValue;
   }
  });
  Hello proxy = (Hello) proxyInstance;
  proxy.say("LYX");
  //可以把InvocationHandler提取出来，单独写一个类，为了方便大家看，这里我用内部类的形式
  class JDKProxy implements InvocationHandler {
   private Object target;
   public JDKProxy(Object target){
    this.target = target;
   }
   public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
    before();
    Object result = method.invoke(target, args);
    after();
    return result;
   }
   private void before(){
    System.out.println("Before");
   }
   private void after(){
    System.out.println("After");
   }
  }
  InvocationHandler ih = new JDKProxy(target);
  Object proxyInstance2 = Proxy.newProxyInstance(target.getClass().getClassLoader(), target.getClass().getInterfaces(), ih);
  Hello proxy2 = (Hello) proxyInstance2;
  proxy2.say("LZHL");
 }
}

<dependencies>
 <!-- https://mvnrepository.com/artifact/cglib/cglib -->
 <dependency>
  <groupId>cglib</groupId>
  <artifactId>cglib</artifactId>
  <version>3.2.4</version>
 </dependency>
</dependencies>

public class Hi {
 public void sayHi(String msg){
  System.out.println("Hi,"+msg);
 }
}

/**
 * @Author LZHL
 * @Create 2017-02-19 13:19
 * @Description
 */
public class Main {
 public static void main(String[] args) {
  Enhancer enhancer = new Enhancer();
  //设置父类
  enhancer.setSuperclass(Hi.class);
  //设置回调函数
  enhancer.setCallback(new MethodInterceptor() {
   public Object intercept(Object target, Method method, Object[] args, MethodProxy methodProxy) throws Throwable {
    System.out.println("before");
    Object retValue = methodProxy.invokeSuper(target, args);
    System.out.println("after");
    return retValue;
   }
  });
  Object proxy = enhancer.create();
  Hi hi = (Hi) proxy;
  hi.sayHi("LXY");
  //可以把MethodInterceptor提取出来，单独写一个类，为了方便大家看，这里我用内部类的形式
  class CGLibProxy implements MethodInterceptor {
   public <T> T getProxy(Class<T> clazz){
    return (T) Enhancer.create(clazz, this);
   }
   public Object intercept(Object target, Method method, Object[] args, MethodProxy proxy) throws Throwable {
    before();
    Object result = proxy.invokeSuper(target, args);
    after();
    return result;
   }
   private void before(){
    System.out.println("Before");
   }
   private void after(){
    System.out.println("After");
   }
  }
  CGLibProxy cgLibProxy = new CGLibProxy();
  Hi hi2 = cgLibProxy.getProxy(Hi.class);
  hi2.sayHi("LZHL");
 }
}