AOP是Spring的重要組成部分砾医，而AOP正是通過代理實現(xiàn)的拿撩。如果代理對象實現(xiàn)了接口，則默認(rèn)使用jdk動態(tài)代理如蚜，也可強制使用cglib代理压恒，如果未實現(xiàn)接口則只能使用cglib代理。
應(yīng)用：對一個操作前后事務(wù)的開啟和提交/回滾

靜態(tài)代理

public interface Fly {
    void fly();
}

public class Bird implements Fly{

    @Override
    public void fly() {
        // TODO Auto-generated method stub
        System.out.println("飛啊飛~");
    }
}

public class ProxyBird implements Fly{

    //維護(hù)一個被代理對象
    Fly bird;
    
    public Fly getBird() {
        return bird;
    }

    public void setBird(Fly bird) {
        this.bird = bird;
    }

    @Override
    public void fly() {
        // TODO Auto-generated method stub
        System.out.println("我代理增強一下你再飛~");
        bird.fly();
    }

}

public class TestBird {
    public static void main(String[] args) {
        Fly bird=new Bird();
        ProxyBird proxyBird=new ProxyBird();
        proxyBird.setBird(bird);
        proxyBird.fly();
    }
}

image.png

JDK動態(tài)代理

public interface UserDao {
    void addUser();
}

public class UserDaoImpl implements UserDao{

    @Override
    public void addUser() {
        // TODO Auto-generated method stub
        System.out.println("添加用戶~");
    }

}

public class TestJDK {
    public static void main(String[] args) {
        UserDao userDao=new UserDaoImpl();
        UserDao proxy=(UserDao)Proxy.newProxyInstance(userDao.getClass().getClassLoader(), userDao.getClass().getInterfaces(), new InvocationHandler() {
            
            @Override
            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                // TODO Auto-generated method stub
                System.out.println("invoke方法前做一些代理");
                method.invoke(userDao, args);
                System.out.println("invoke方法后做一些代理");
                return proxy;
            }
        });
        proxy.addUser();
    }
}

image.png

CGLIB代理

public class UserService {
    
    public void addUser(){
        System.out.println("我不需要接口就可以被代理哦~");
    }
}

public class Testcglb {
    public static void main(String[] args) {
        UserService userService=new UserService();
        Enhancer enhancer = new Enhancer();  
        enhancer.setSuperclass(userService.getClass());  
          
        // 3错邦、設(shè)置回調(diào)函數(shù)  
        enhancer.setCallback(new MethodInterceptor() {  
              
            @Override  
            public Object intercept(Object proxy, Method method, Object[] args,  
                    MethodProxy methodProxy) throws Throwable {  
                if(method.getName().equals("run")){  
                    System.out.println("userService的add方法被攔截了探赫。。撬呢。伦吠。");  
                    Object invoke = method.invoke(proxy, args);  
                    System.out.println("真實方法攔截之后。魂拦。毛仪。。");  
                    return invoke;  
                }  
                  
                // 不攔截  
                return method.invoke(proxy, args);  
            }  
        });  
        UserService proxy = (UserService) enhancer.create();  
          
        proxy.run();  
    }
}