別再用 BeanUtils 了，這款 PO VO DTO 轉換神器不香麽？

2024-05-28碼農

老鐵們是不是經常為寫一些實體轉換的原始程式碼感到頭疼，尤其是實體欄位特別多的時候。介紹一個開源計畫 mapstruct ，可以輕松優雅的進行轉換，簡化你的程式碼。當然有的人喜歡寫get set，或者用BeanUtils 進行復制，程式碼只是工具，本文只是提供一種思路。

先貼下官網地址吧：https://mapstruct.org/

廢話不多說，上程式碼：

pom 配置：

<properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> <maven.compiler.source>1.8</maven.compiler.source> <maven.compiler.target>1.8</maven.compiler.target> <org.mapstruct.version>1.4.1.Final</org.mapstruct.version> <org.projectlombok.version>1.18.12</org.projectlombok.version> </properties> <dependencies> <dependency> <groupId>org.mapstruct</groupId> <artifactId>mapstruct</artifactId> <version>${org.mapstruct.version}</version> </dependency>  <dependency> <groupId>org.projectlombok</groupId> <artifactId>lombok</artifactId> <version>${org.projectlombok.version}</version> <scope>provided</scope> </dependency>  <dependency> <groupId>org.mapstruct</groupId> <artifactId>mapstruct-processor</artifactId> <version>${org.mapstruct.version}</version> <scope>provided</scope> </dependency> </dependencies> <build> <plugins> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-compiler-plugin</artifactId> <version>3.8.1</version> <configuration> <source>1.8</source> <target>1.8</target> <annotationProcessorPaths> <path> <groupId>org.projectlombok</groupId> <artifactId>lombok</artifactId> <version>${org.projectlombok.version}</version> </path> <path> <groupId>org.mapstruct</groupId> <artifactId>mapstruct-processor</artifactId> <version>${org.mapstruct.version}</version> </path> </annotationProcessorPaths> </configuration> </plugin> </plugins> </build>

關於lombok和mapstruct的版本相容問題多說幾句，maven外掛程式要使用3.6.0版本以上、lombok使用1.16.16版本以上，另外編譯的lombok mapstruct的外掛程式不要忘了加上。否則會出現下面的錯誤：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。還有就是缺少建構函式也會拋異常。

@Data @Builder @AllArgsConstructor @NoArgsConstructor public classStudent{ private String name; privateint age; private GenderEnum gender; private Double height; private Date birthday; } publicenum GenderEnum { Male("1", "男"), Female("0", "女"); private String code; private String name; public String getCode(){ returnthis.code; } public String getName(){ returnthis.name; } GenderEnum(String code, String name) { this.code = code; this.name = name; } } @Data @Builder @AllArgsConstructor @NoArgsConstructor public classStudentVO{ private String name; privateint age; private String gender; private Double height; private String birthday; } @Mapper publicinterfaceStudentMapper{ 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，需要手寫的部份就是這個Mapper的介面，編譯完成後會自動生成相應的實作類

然後就可以直接用mapper進行實體的轉換了

public classTest{ publicstaticvoidmain(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); //這行程式碼便是實際要用的程式碼 StudentVO studentVO = StudentMapper.INSTANCE.student2StudentVO(student); System.out.println(studentVO); } }

mapper可以進行欄位對映，改變欄位型別，指定格式化的方式，包括一些日期的預設處理。

可以手動指定格式化的方法：

@Mapper publicinterfaceStudentMapper{ 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對映處理，下面介紹一些高級用法

1、List 轉換

內容對映基於上面的mapping配置

@Mapper publicinterfaceStudentMapper{ 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<StudentVO> students2StudentVOs(List<Student> studentList); } publicstaticvoidmain(String[] args){ Student student = Student.builder().name("小明").age(6).gender(GenderEnum.Male).height(121.1).birthday(new Date()).build(); List<Student> list = new ArrayList<>(); list.add(student); List<StudentVO> result = StudentMapper.INSTANCE.students2StudentVOs(list); System.out.println(result); }

2、多物件轉換到一個物件

@Data @Builder @AllArgsConstructor @NoArgsConstructor public classStudent{ private String name; privateint age; private GenderEnum gender; private Double height; private Date birthday; } @Data @AllArgsConstructor @Builder @NoArgsConstructor public classCourse{ private String courseName; privateint sortNo; privatelong id; } @Data @Builder @AllArgsConstructor @NoArgsConstructor public classStudentVO{ private String name; privateint age; private String gender; private Double height; private String birthday; private String course; } @Mapper publicinterfaceStudentMapper{ 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 classTest{ publicstaticvoidmain(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、預設值

@Mapper publicinterfaceStudentMapper{ 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); }