这篇文章主要讲解了“Spring BeanUtils如何忽略空值拷贝”，文中的讲解内容简单清晰，易于学习与理解，下面请大家跟着小编的思路慢慢深入，一起来研究和学习“Spring BeanUtils如何忽略空值拷贝”吧！
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<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); }}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<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;@Datapublic 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;@Datapublic 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;@RestControllerpublic 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
<?xml version="1.0" encoding="UTF-8"?><project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>2.3.0.RELEASE</version> <relativePath/> <!-- lookup parent from repository --> </parent> <groupId>com.example</groupId> <artifactId>demo_SpringBoot</artifactId> <version>0.0.1-SNAPSHOT</version> <name>demo_SpringBoot</name> <description>Demo project for Spring Boot</description> <properties> <java.version>1.8</java.version> </properties> <dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <dependency> <groupId>org.projectlombok</groupId> <artifactId>lombok</artifactId> <version>1.16.20</version> <scope>provided</scope> </dependency> </dependencies> <build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> <version>2.3.0.RELEASE</version> </plugin> </plugins> </build> </project>感谢各位的阅读，以上就是“Spring BeanUtils如何忽略空值拷贝”的内容了，经过本文的学习后，相信大家对Spring BeanUtils如何忽略空值拷贝这一问题有了更深刻的体会，具体使用情况还需要大家实践验证。这里是编程网，小编将为大家推送更多相关知识点的文章，欢迎关注！
