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<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;
@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;
}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
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>其他网址
Spring BeanUtils忽略空值拷贝用法 - 掘金
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