Spring BeanUtils忽略空值拷贝的方法示例代码

本文用示例介绍Spring（SpringBoot）如何使用BeanUtils拷贝对象属性忽略空置，忽略null值拷贝属性的用法，代码简单易懂，对大家的学习或工作具有一定的参考借鉴价值，需要的朋友参考下吧

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：

Spring的（推荐）：org.springframework.beans.BeanUtilsApache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)

获取null属性名（工具类）

可以自己写一个工具类，用来获取对象里所有null的属性名字。

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 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); } }

示例

本处为了全面，将以下几种情况都考虑进去：

继承了某个类
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 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; 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; }

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

访问：http://localhost:8080/test/

后端结果：

[updateTime, content] ------------------------------ {"createTime":"2022-03-17 19:58:32","updateTime":null,"deletedFlag":0,"id":10,"title":"Java实战","content":null,"user":{"id":null,"userName":null,"nickName":null,"status":null}}

结论

可以获取父类的null的属性名
不可以获取属性的null的属性名

其他文件

pom.xml

  4.0.0 org.springframework.bootspring-boot-starter-parent2.3.0.RELEASEcom.exampledemo_SpringBoot0.0.1-SNAPSHOTdemo_SpringBootDemo project for Spring Boot 1.8  org.springframework.bootspring-boot-starter-web org.projectlomboklombok1.16.20provided   org.springframework.bootspring-boot-maven-plugin2.3.0.RELEASE