別再用 BeanUtils 了，這款 PO VO DTO 轉換神器不香么？

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老鐵們是不是經(jīng)常為寫一些實體轉換的原始代碼感到頭疼，尤其是實體字段特別多的時候。介紹一個開源項目 mapstruct ，可以輕松優(yōu)雅的進行轉換，簡化你的代碼。當然有的人喜歡寫get set，或者用BeanUtils 進行復制，代碼只是工具，本文只是提供一種思路。

先貼下官網(wǎng)地址吧：https://mapstruct.org/

廢話不多說，上代碼：

pom 配置：

<properties>
????????<project.build.sourceEncoding>UTF-8project.build.sourceEncoding>
????????<maven.compiler.source>1.8maven.compiler.source>
????????<maven.compiler.target>1.8maven.compiler.target>
????????<org.mapstruct.version>1.4.1.Finalorg.mapstruct.version>
????????<org.projectlombok.version>1.18.12org.projectlombok.version>
properties>

<dependencies>
????????<dependency>
????????????<groupId>org.mapstructgroupId>
????????????<artifactId>mapstructartifactId>
????????????<version>${org.mapstruct.version}version>
????????dependency>

????????
????????<dependency>
????????????<groupId>org.projectlombokgroupId>
????????????<artifactId>lombokartifactId>
????????????<version>${org.projectlombok.version}version>
????????????<scope>providedscope>
????????dependency>

????????
?????<dependency>
????????????<groupId>org.mapstructgroupId>
????????????<artifactId>mapstruct-processorartifactId>
????????????<version>${org.mapstruct.version}version>
????????????<scope>providedscope>
????????dependency>

dependencies>

<build>
????????<plugins>
????????????<plugin>
????????????????<groupId>org.apache.maven.pluginsgroupId>
????????????????<artifactId>maven-compiler-pluginartifactId>
????????????????<version>3.8.1version>
????????????????<configuration>
????????????????????<source>1.8source>
????????????????????<target>1.8target>
????????????????????<annotationProcessorPaths>
????????????????????????<path>
????????????????????????????<groupId>org.projectlombokgroupId>
????????????????????????????<artifactId>lombokartifactId>
????????????????????????????<version>${org.projectlombok.version}version>
????????????????????????path>
????????????????????????<path>
????????????????????????????<groupId>org.mapstructgroupId>
????????????????????????????<artifactId>mapstruct-processorartifactId>
????????????????????????????<version>${org.mapstruct.version}version>
????????????????????????path>
????????????????????annotationProcessorPaths>
????????????????configuration>
????????????plugin>
????????plugins>
????build>

關于lombok和mapstruct的版本兼容問題多說幾句，maven插件要使用3.6.0版本以上、lombok使用1.16.16版本以上，另外編譯的lombok mapstruct的插件不要忘了加上。否則會出現(xiàn)下面的錯誤：No property named "aaa" exists in source parameter(s). Did you mean "null"?

這種異常就是lombok編譯異常導致缺少get setter方法造成的。還有就是缺少構造函數(shù)也會拋異常。

@Data
@Builder
@AllArgsConstructor
@NoArgsConstructor
public?class?Student?{

????private?String?name;
????private?int?age;
????private?GenderEnum?gender;
????private?Double?height;
????private?Date?birthday;

}
public?enum?GenderEnum?{
????Male("1",?"男"),
????Female("0",?"女");

????private?String?code;
????private?String?name;

????public?String?getCode()?{
????????return?this.code;
????}

????public?String?getName()?{
????????return?this.name;
????}

????GenderEnum(String?code,?String?name)?{
????????this.code?=?code;
????????this.name?=?name;
????}
}
@Data
@Builder
@AllArgsConstructor
@NoArgsConstructor
public?class?StudentVO?{
????private?String?name;
????private?int?age;
????private?String?gender;
????private?Double?height;
????private?String?birthday;
}
@Mapper
public?interface?StudentMapper?{

????StudentMapper?INSTANCE?=?Mappers.getMapper(StudentMapper.class);

????@Mapping(source?=?"gender.name",?target?=?"gender")
????@Mapping(source?=?"birthday",?target?=?"birthday",?dateFormat?=?"yyyy-MM-dd?HH:mm:ss")
????StudentVO?student2StudentVO(Student?student);

}

實體類是開發(fā)過程少不了的，就算是用工具生成肯定也是要有的，需要手寫的部分就是這個Mapper的接口，編譯完成后會自動生成相應的實現(xiàn)類

然后就可以直接用mapper進行實體的轉換了

public?class?Test?{

????public?static?void?main(String[]?args)?{

????????Student?student?=?Student.builder().name("小明").age(6).gender(GenderEnum.Male).height(121.1).birthday(new?Date()).build();
????????System.out.println(student);
????????//這行代碼便是實際要用的代碼
????????StudentVO?studentVO?=?StudentMapper.INSTANCE.student2StudentVO(student);
????????System.out.println(studentVO);

????}

}

mapper可以進行字段映射，改變字段類型，指定格式化的方式，包括一些日期的默認處理。

可以手動指定格式化的方法：

@Mapper
public?interface?StudentMapper?{

????StudentMapper?INSTANCE?=?Mappers.getMapper(StudentMapper.class);

????@Mapping(source?=?"gender",?target?=?"gender")
????@Mapping(source?=?"birthday",?target?=?"birthday",?dateFormat?=?"yyyy-MM-dd?HH:mm:ss")
????StudentVO?student2StudentVO(Student?student);

????default?String?getGenderName(GenderEnum?gender)?{
????????return?gender.getName();
????}

}

上面只是最簡單的實體映射處理，下面介紹一些高級用法

1、List 轉換

屬性映射基于上面的mapping配置

@Mapper
public?interface?StudentMapper?{

????StudentMapper?INSTANCE?=?Mappers.getMapper(StudentMapper.class);

????@Mapping(source?=?"gender.name",?target?=?"gender")
????@Mapping(source?=?"birthday",?target?=?"birthday",?dateFormat?=?"yyyy-MM-dd?HH:mm:ss")
????StudentVO?student2StudentVO(Student?student);


????List?students2StudentVOs(List?studentList);

}
public?static?void?main(String[]?args)?{

????Student?student?=?Student.builder().name("小明").age(6).gender(GenderEnum.Male).height(121.1).birthday(new?Date()).build();

????List?list?=?new?ArrayList<>();
????list.add(student);
????List?result?=?StudentMapper.INSTANCE.students2StudentVOs(list);
????System.out.println(result);
}

2、多對象轉換到一個對象

@Data
@Builder
@AllArgsConstructor
@NoArgsConstructor
public?class?Student?{

????private?String?name;
????private?int?age;
????private?GenderEnum?gender;
????private?Double?height;
????private?Date?birthday;

}
@Data
@AllArgsConstructor
@Builder
@NoArgsConstructor
public?class?Course?{

????private?String?courseName;
????private?int?sortNo;
????private?long?id;

}
@Data
@Builder
@AllArgsConstructor
@NoArgsConstructor
public?class?StudentVO?{
????private?String?name;
????private?int?age;
????private?String?gender;
????private?Double?height;
????private?String?birthday;
????private?String?course;
}
@Mapper
public?interface?StudentMapper?{

????StudentMapper?INSTANCE?=?Mappers.getMapper(StudentMapper.class);

????@Mapping(source?=?"student.gender.name",?target?=?"gender")
????@Mapping(source?=?"student.birthday",?target?=?"birthday",?dateFormat?=?"yyyy-MM-dd?HH:mm:ss")
????@Mapping(source?=?"course.courseName",?target?=?"course")
????StudentVO?studentAndCourse2StudentVO(Student?student,?Course?course);

}
public?class?Test?{

????public?static?void?main(String[]?args)?{

????????Student?student?=?Student.builder().name("小明").age(6).gender(GenderEnum.Male).height(121.1).birthday(new?Date()).build();
????????Course?course?=?Course.builder().id(1L).courseName("語文").build();

????????StudentVO?studentVO?=?StudentMapper.INSTANCE.studentAndCourse2StudentVO(student,?course);
????????System.out.println(studentVO);
????}

}

3、默認值

@Mapper
public?interface?StudentMapper?{

????StudentMapper?INSTANCE?=?Mappers.getMapper(StudentMapper.class);

????@Mapping(source?=?"student.gender.name",?target?=?"gender")
????@Mapping(source?=?"student.birthday",?target?=?"birthday",?dateFormat?=?"yyyy-MM-dd?HH:mm:ss")
????@Mapping(source?=?"course.courseName",?target?=?"course")
????@Mapping(target?=?"name",?source?=?"student.name",?defaultValue?=?"張三")
????StudentVO?studentAndCourse2StudentVO(Student?student,?Course?course);

}

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