对象 的 复制

import org.springframework.beans.BeanUtils;

BeanUtils.copyProperties(userMessage, userMessageCopy);

User user = new User()
user.setId(1).setName("张三").setAge(13);

User userCopy = new User()

​​​​​​​BeanUtils.copyProperties(user, userCopy);

Integer userId = userCopy.getId();
system.out.print(userId);    // 1