public interface ISubject {

  public int add(int a, int b);
}

public class Subject implements ISubject {
  @Override
  public int add(int a, int b) {
    return a + b;
  }
}

public class JdkProxy implements InvocationHandler {

  public Object target;

  public JdkProxy(Object target) {
    this.target = target;
  }

  //第一個是類加載器,采用了target本身的類加載器
  //第二個是把生成的動態(tài)代理對象下掛在哪些接口下面,該寫法就是將生成的代理對象放在target真實對象所實現(xiàn)的所有接口下.Subject對象的接口顯然是ISubject,代理對象可以這樣聲明:ISubject proxy =xxxx;
  //第三個是定義實現(xiàn)方法邏輯的代理類,this表示當(dāng)前對象,它`必須實現(xiàn)InvocationHandler接口的invoke方法,它就是代理邏輯方法.
  public Object getInstance() {
    Object o = Proxy.newProxyInstance(target.getClass().getClassLoader(), target.getClass().getInterfaces(), this);
    return o;
  }


  //proxy:代理對象,就是getInstance方法生成的對象
  //method,當(dāng)前調(diào)度的方法
  //args:調(diào)度方法的參數(shù)
  @Override
  public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
    System.out.println(method.getName() + "方法執(zhí)行前");
    Object object = method.invoke(target, args);
    System.out.println(object);
    System.out.println(method.getName() + "方法執(zhí)行后");
    return object;
  }
}

public class ProxyTest {

  public static void main(String[] args) {
    Subject subject = new Subject();
    JdkProxy jdk = new JdkProxy(subject);
    ISubject proxy = (ISubject) jdk.getInstance();
    proxy.add(2, 3);
  }
}