這篇文章主要講解了“Spring BeanUtils如何忽略空值拷貝”，文中的講解內容簡單清晰，易于學習與理解，下面請大家跟著小編的思路慢慢深入，一起來研究和學習“Spring BeanUtils如何忽略空值拷貝”吧！
BeanUtils類所在的包
有兩個包都提供了BeanUtils類：
Spring的（推薦）：org.springframework.beans.BeanUtilsApache的：org.apache.commons.beanutils.BeanUtils
忽略null值拷貝屬性的用法
BeanUtils.copyProperties(Object source, Object target, String... ignoreProperties)
可以自己寫一個工具類，用來獲取對象里所有null的屬性名字。
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);
}
}本處為了全面，將以下幾種情況都考慮進去：
繼承了某個類
某個屬性是個Entity
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);
}
}基礎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：被鎖定
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;
}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實戰");
// blogRequest.setContent("本文介紹獲取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";
}
}訪問：http://localhost:8080/test/
后端結果：
[updateTime, content]
------------------------------
{"createTime":"2022-03-17 19:58:32","updateTime":null,"deletedFlag":0,"id":10,"title":"Java實戰","content":null,"user":{"id":null,"userName":null,"nickName":null,"status":null}}結論
可以獲取父類的null的屬性名
不可以獲取屬性的null的屬性名
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>
感謝各位的閱讀，以上就是“Spring BeanUtils如何忽略空值拷貝”的內容了，經過本文的學習后，相信大家對Spring BeanUtils如何忽略空值拷貝這一問題有了更深刻的體會，具體使用情況還需要大家實踐驗證。這里是億速云，小編將為大家推送更多相關知識點的文章，歡迎關注！
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