静态代理

一、自己理解

所谓静态代理，其实就是代理类由自己实现，编译时期.class文件已经存在。代理类和委托类(被代理类)，实现相同接口，在委托类中实现具体的业务逻辑，而代理类这做数据预处理等工作

二、代码实现

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

IUserDao.java文件
public interface IUserDao {
    void saveUser(User user);
    int updateUser(User user);
}

UserDaoImpl.java文件
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;
    }
}

UserStaticProxy.java文件
public class UserStaticProxy implements IUserDao {

    private IUserDao userDao = null;

    public UserStaticProxy(IUserDao userDao) {
        this.userDao = userDao;
    }


    @Override
    public void saveUser(User user) {
        System.out.println("Proxy saveUser before.");
        userDao.saveUser(user);
        System.out.println("Proxy saveUser after.");
    }

    @Override
    public int updateUser(User user) {
        System.out.println("Proxy updateUser before.");
        int affectRecords = userDao.updateUser(user);
        System.out.println("Proxy updateUser after.");
        return affectRecords;
    }
}

三、测试

public class UserProxyTest {

    @Test
    public void testStaticProxy() {
        User user = new User();
        IUserDao userDao = new UserDaoImpl();
        IUserDao proxyUserDao = new UserStaticProxy(userDao);
        proxyUserDao.saveUser(user);
        proxyUserDao.updateUser(user);
    }
}