cglib动态代理(需要cglib.jar)

1.原理

cglib是针对类来实现代理的，他的原理是对指定的目标类生成一个子类，并覆盖其中方法实现增强，但因为采用的是继承，所以不能对final修饰的类进行代理
API介绍：
    Enhancer enhancer = new Enhancer(); // cglib增强类
    enhancer.setSuperclass(target.getClass());  // 设置目标类
    enhancer.setCallback(this); // 设置委托对象
    return (T) enhancer.create();   // 创建代理对象
    
    MethodInterceptor 方法拦截接口

2.具体实现

2.1 User.java

@Data
@NoArgsConstructor
@AllArgsConstructor
@ToString
public class User {
    private String username;
    private String password;
}

2.2 委托类

public class UserDaoImpl implements IUserDao {
    @Override
    public void saveUser(User user) {
        System.out.println("UserDaoImpl save user.");
    }

    @Override
    public int updateUser(User user) {
        System.out.println("UserDaoImpl update user.");
        return 0;
    }
}

2.3 代理类

public class UserCglibProxy<T> implements MethodInterceptor {

    private T target;

    public T proxy(T target) {
        this.target = target;
        Enhancer enhancer = new Enhancer();
        enhancer.setSuperclass(target.getClass());
        enhancer.setCallback(this);
        return (T) enhancer.create();
    }

    @Override
    public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {
        System.out.println("ProxyMethod before.");
        Object result = methodProxy.invoke(target, objects);
        System.out.println("ProxyMethod after.");
        return result;
    }
}

3.测试

@Test
public void testCglib() {
    User user = new User();
    UserDaoImpl userDao = new UserDaoImpl();
    UserDaoImpl userDaoProxy = new UserCglibProxy<UserDaoImpl>().proxy(userDao);
    userDaoProxy.saveUser(user);
}