Spring工具类--BeanUtils忽略空值拷贝--方法/实例

阳光穿透心脏的1/2处 2023-09-30 09:37 24阅读 0赞

原文网址：[Spring工具类--BeanUtils忽略空值拷贝--方法/实例\_IT利刃出鞘的博客-CSDN博客\_bean拷贝忽略空值][Spring_--BeanUtils_--_IT_-CSDN_bean]

## 简介 ##

**说明**

本文用示例介绍Spring（SpringBoot）如何使用BeanUtils拷贝对象属性（忽略空值）。

**BeanUtils类所在的包**

有两个包都提供了BeanUtils类：

1.  Spring的（推荐）：org.springframework.beans.BeanUtils
2.  Apache的：org.apache.commons.beanutils.BeanUtils

**忽略null值拷贝属性的用法**

BeanUtils.copyProperties(Object source, Object target, String... ignoreProperties)

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## 示例 ##

本处为了全面，将以下几种情况都考虑进去：

1.  继承了某个类
2.  某个属性是个Entity

### 工具类 ###

package com.example.util;
    
    import org.springframework.beans.BeanWrapper;
    import org.springframework.beans.BeanWrapperImpl;
    
    import java.beans.PropertyDescriptor;
    import java.util.HashSet;
    import java.util.Set;
    
    public class PropertyUtil {
        public static String[] getNullPropertyNames(Object source) {
            BeanWrapper src = new BeanWrapperImpl(source);
            PropertyDescriptor[] pds = src.getPropertyDescriptors();
    
            Set<String> emptyNames = new HashSet<>();
    
            for (PropertyDescriptor pd : pds) {
                //check if value of this property is null then add it to the collection
                Object srcValue = src.getPropertyValue(pd.getName());
                if (srcValue == null){
                    emptyNames.add(pd.getName());
                }
            }
    
            String[] result = new String[emptyNames.size()];
            return emptyNames.toArray(result);
        }
    }

### Entity ###

**基础Entity**

package com.example.entity;
    
    import com.fasterxml.jackson.annotation.JsonFormat;
    import lombok.Data;
    
    import java.time.LocalDateTime;
    
    @Data
    public class BaseEntity {
        @JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss",timezone="GMT+8")
        private LocalDateTime createTime;
    
        @JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss",timezone="GMT+8")
        private LocalDateTime updateTime;
    
        private Long deletedFlag;
    }

**User**

package com.example.entity;
    
    import lombok.Data;
    
    @Data
    public class User {
        private Long id;
    
        private String userName;
    
        private String nickName;
    
        // 0:正常 1：被锁定
        private Integer status;
    }

**Blog**

package com.example.entity;
    
    import lombok.Data;
    import lombok.EqualsAndHashCode;
    
    @Data
    @EqualsAndHashCode(callSuper = true)
    public class Blog extends BaseEntity{
        private Long id;
    
        private String title;
    
        private String content;
    
        private User user;
    }

### VO ###

package com.example.vo;
    
    import com.example.entity.BaseEntity;
    import com.example.entity.User;
    import lombok.Data;
    import lombok.EqualsAndHashCode;
    
    @Data
    @EqualsAndHashCode(callSuper = true)
    public class BlogRequest extends BaseEntity {
        private Long id;
    
        private String title;
    
        private String content;
    
        private User user;
    }

### Controller ###

package com.example.controller;
    
    import com.example.entity.Blog;
    import com.example.entity.User;
    import com.example.util.PropertyUtil;
    import com.example.vo.BlogRequest;
    import com.fasterxml.jackson.core.JsonProcessingException;
    import com.fasterxml.jackson.databind.ObjectMapper;
    import org.springframework.beans.BeanUtils;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.web.bind.annotation.GetMapping;
    import org.springframework.web.bind.annotation.RestController;
    
    import java.time.LocalDateTime;
    import java.util.Arrays;
    
    @RestController
    public class HelloController {
        @Autowired
        private ObjectMapper objectMapper;
    
        @GetMapping("/test")
        public String test() {
            BlogRequest blogRequest = new BlogRequest();
            blogRequest.setId(10L);
            blogRequest.setTitle("Java实战");
            // blogRequest.setContent("本文介绍获取null的字段名的方法");
            blogRequest.setUser(new User());
            blogRequest.setCreateTime(LocalDateTime.now());
            // blogRequest.setCreateTime(LocalDateTime.now());
            blogRequest.setDeletedFlag(0L);
    
            User user = new User();
            user.setId(15L);
            user.setUserName("Tony");
            // user.setNickName("Iron Man");
            // user.setStatus(1);
    
            String[] nullPropertyNames = PropertyUtil.getNullPropertyNames(blogRequest);
            System.out.println(Arrays.toString(nullPropertyNames));
    
            System.out.println("------------------------------");
            Blog blog = new Blog();
            BeanUtils.copyProperties(blogRequest, blog, nullPropertyNames);
    
            try {
                System.out.println(objectMapper.writeValueAsString(blog));
            } catch (JsonProcessingException e) {
                e.printStackTrace();
            }
    
            return "test success";
        }
    }

### 测试 ###

上边是文章的部分内容，为便于维护，全文已转移到此网址：[Spring工具类-BeanUtils忽略空值拷贝 - 自学精灵][Spring_-BeanUtils_ -]

[Spring_--BeanUtils_--_IT_-CSDN_bean]: https://knife.blog.csdn.net/article/details/123532488
[Link 1]: https://app.yinxiang.com/fx/d2ac6ff4-94c5-4e5f-9d4f-f5dfc344ede6
[Spring_-BeanUtils_ -]: https://learn.skyofit.com/archives/2258