java的日常开发经常会出现对象属性拷贝赋值的场景,比较常见的解决方式是使用org.springframework.beans.BeanUtils的copyProperties类。该类能够通过反射机制来获取源对象和目的对象的属性，并将对应的属性值进行复制，从而减少手动编写属性复制代码的工作量，提高代码的可读性和维护性。然而在使用过程中，需要注意以下几种情况会导致属性复制失效：

1. 类型不匹配

@Data
public class SourceBean {
    private Long age;
}

@Data
public class TargetBean {
    private String age;
}

public class Test {

    public static void main(String[] args) {
        SourceBean source = new SourceBean();
        source.setAge(25L);

        TargetBean target = new TargetBean();
        BeanUtils.copyProperties(source, target);

        System.out.println(target.getAge());  //拷贝赋值失败，输出null
    }
}

2. 属性名称不一致

public class SourceBean {
    private String username;
}

public class TargetBean {
    private String userName;
}

 SourceBean source = new SourceBean();
 source.setUsername("捡田螺的小男孩");

 TargetBean target = new TargetBean();
 BeanUtils.copyProperties(source, target);

 System.out.println(target.getUserName());   // 输出为 null

3. Null 值覆盖

@Data
public class SourceBean {
    private String name;
    private String address;
}

@Data
public class TargetBean {
    private String name;
    private String address;
}

SourceBean source = new SourceBean();
source.setName("John");
source.setAddress(null);

TargetBean target = new TargetBean();
target.setAddress("田螺address");
BeanUtils.copyProperties(source, target);

System.out.println(target.getAddress());  // 输出为 null

4. Boolean类型数据+is属性开头的坑

@Data
public class SourceBean {
    private boolean isTianLuo;
}

@Data
public class TargetBean {
    private Boolean isTianLuo;
}


SourceBean source = new SourceBean();
source.setTianLuo(true);

TargetBean target = new TargetBean();
BeanUtils.copyProperties(source, target);
System.out.println(target.getIsTianLuo()); // 输出为 null