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.BeanUtils
- 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)
获取null属性名(工具类)
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
可以自己写一个工具类,用来获取对象里所有null或者空字符串的属性名字。
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[] readEmptyPropertyNames(Object source) { BeanWrapper src = new BeanWrapperImpl(source); PropertyDescriptor[] pds = src.getPropertyDescriptors(); Set<String> emptyNames = new HashSet<>(); for (PropertyDescriptor pd : pds) { String filedName = pd.getName(); Object srcValue = src.getPropertyValue(pd.getName()); if (srcValue == null) { emptyNames.add(filedName); } else { if (srcValue instanceof String) { if (!StringUtils.hasText((String) srcValue)) { emptyNames.add(filedName); } } } } 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
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
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>
请先
!