public interface ICalculator {
 //加法运算
 public int add(int a,int b);
 //减法
 public int subtract(int a,int b);
 //乘法
 public int multiply(int a,int b);
 //除法
 public int devide(int a,int b);
}

public class CalculatorImpl implements ICalculator{
 @Override
 public int add(int a, int b) {
  return a + b;
 }
 @Override
 public int subtract(int a, int b) {
  return a - b;
 }
 @Override
 public int multiply(int a, int b) {
  return a * b;
 }
 @Override
 public int devide(int a, int b) {
  return a / b;
 }
}

public class TestHandler implements InvocationHandler {
 private Object targetObject;
 private int useTimes;
 //绑定委托对象，并返回代理类
 public Object bind(Object targetObject){
  this.targetObject = targetObject;
  return Proxy.newProxyInstance(targetObject.getClass().getClassLoader(),targetObject.getClass().getInterfaces(),this);
 }
 @Override
 public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
  //do something
  before();
  Object result = method.invoke(targetObject,args);
  after();
  return result;
 }
 private void before(){
  System.out.println("we can do something before calculate.");
 }
 private void after(){
  useTimes++;
  System.out.println("已使用："+useTimes+"次");
 }
}

public class TestProxy {
 public static void main(String[] args) {
  TestHandler proxy = new TestHandler();
  ICalculator calculator = (ICalculator)proxy.bind(new CalculatorImpl());
  int result = calculator.add(1,2);
  System.out.println("result is:"+result);
  result = calculator.subtract(3,2);
  System.out.println("result is:"+result);
  result = calculator.multiply(4,6);
  System.out.println("result is:"+result);
  result = calculator.devide(6,2);
  System.out.println("result is:"+result);
 }
}

we can do something before calculate.
已使用：1次
result is:3
we can do something before calculate.
已使用：2次
result is:1
we can do something before calculate.
已使用：3次
result is:24
we can do something before calculate.
已使用：4次
result is:3

public class CGLibProxy implements MethodInterceptor {
 private int useTimes;
 private Object target;

 public Object getInstance(Object target){
  this.target=target;
  Enhancer enhancer =new Enhancer();
  enhancer.setSuperclass(this.target.getClass());
  enhancer.setCallback(this);
  return enhancer.create();
 }
 @Override
 public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {
  before();
  Object result = methodProxy.invokeSuper(o,objects);
  after();
  return result;
 }
 private void before(){
  System.out.println("we can do something before calculate.");
 }
 private void after(){
  useTimes++;
  System.out.println("已使用："+useTimes+"次");
 }
}

public class TestCGLibProxy {
 public static void main(String[] args) {
  CGLibProxy cgLibProxy = new CGLibProxy();
  ICalculator calculator = (ICalculator) cgLibProxy.getInstance(new CalculatorImpl());
  int result = calculator.add(1,2);
  System.out.println("result is:"+result);
  result = calculator.subtract(3,2);
  System.out.println("result is:"+result);
  result = calculator.multiply(4,6);
  System.out.println("result is:"+result);
  result = calculator.devide(6,2);
  System.out.println("result is:"+result);
 }
}

we can do something before calculate.
已使用：1次
result is:3
we can do something before calculate.
已使用：2次
result is:1
we can do something before calculate.
已使用：3次
result is:24
we can do something before calculate.
已使用：4次
result is:3