Spring Bean复制属性忽略子对象的空值

import org.springframework.beans.BeanUtils;

public class SourceBean {
    private String name;
    private SubBean subBean;

    // getter and setter methods

    public static class SubBean {
        private String subName;

        // getter and setter methods
    }

    public static class TargetBean {
        private String name;
        private SubBean subBean;

        // getter and setter methods
    }

    public static void main(String[] args) {
        SourceBean sourceBean = new SourceBean();
        sourceBean.setName("John");
        sourceBean.setSubBean(null);

        TargetBean targetBean = new TargetBean();

        BeanUtils.copyProperties(sourceBean, targetBean, "subBean");

        System.out.println(targetBean.getName()); // Output: John
        System.out.println(targetBean.getSubBean()); // Output: null
    }
}