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老铁们是不是经常为写一些实体转换的原始代码感到头疼，尤其是实体字段特别多的时候。介绍一个开源项目 mapstruct ，可以轻松优雅的进行转换，简化你的代码。当然有的人喜欢写get set，或者用BeanUtils 进行复制，代码只是工具，本文只是提供一种思路。
先贴下官网地址吧：https://mapstruct.org/
废话不多说，上代码：
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>${org.mapstruct.version}</version></dependency><!--lombokdependenciesshouldnotenduponclasspath--><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><version>${org.projectlombok.version}</version><scope>provided</scope></dependency><!--idea2018.1.1之前的版本需要添加下面的配置，后期的版本就不需要了，可以注释掉，我自己用的2019.3--><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>关于lombok和mapstruct的版本兼容问题多说几句，maven插件要使用3.6.0版本以上、lombok使用1.16.16版本以上，另外编译的lombok mapstruct的插件不要忘了加上。否则会出现下面的错误：No property named "aaa" exists in source parameter(s). Did you mean "null"?
这种异常就是lombok编译异常导致缺少get setter方法造成的。还有就是缺少构造函数也会抛异常。
@Data@Builder@AllArgsConstructor@NoArgsConstructorpublicclassStudent{privateStringname;privateintage;privateGenderEnumgender;privateDoubleheight;privateDatebirthday;}publicenumGenderEnum{Male("1","男"),Female("0","女");privateStringcode;privateStringname;publicStringgetCode(){returnthis.code;}publicStringgetName(){returnthis.name;}GenderEnum(Stringcode,Stringname){this.code=code;this.name=name;}}@Data@Builder@AllArgsConstructor@NoArgsConstructorpublicclassStudentVO{privateStringname;privateintage;privateStringgender;privateDoubleheight;privateStringbirthday;}@MapperpublicinterfaceStudentMapper{StudentMapperINSTANCE=Mappers.getMapper(StudentMapper.class);@Mapping(source="gender.name",target="gender")@Mapping(source="birthday",target="birthday",dateFormat="yyyy-MM-ddHH:mm:ss")StudentVOstudent2StudentVO(Studentstudent);}实体类是开发过程少不了的，就算是用工具生成肯定也是要有的，需要手写的部分就是这个Mapper的接口，编译完成后会自动生成相应的实现类
然后就可以直接用mapper进行实体的转换了
publicclassTest{publicstaticvoidmain(String[]args){Studentstudent=Student.builder().name("小明").age(6).gender(GenderEnum.Male).height(121.1).birthday(newDate()).build();System.out.println(student);//这行代码便是实际要用的代码StudentVOstudentVO=StudentMapper.INSTANCE.student2StudentVO(student);System.out.println(studentVO);}}mapper可以进行字段映射，改变字段类型，指定格式化的方式，包括一些日期的默认处理。
可以手动指定格式化的方法：
@MapperpublicinterfaceStudentMapper{StudentMapperINSTANCE=Mappers.getMapper(StudentMapper.class);@Mapping(source="gender",target="gender")@Mapping(source="birthday",target="birthday",dateFormat="yyyy-MM-ddHH:mm:ss")StudentVOstudent2StudentVO(Studentstudent);defaultStringgetGenderName(GenderEnumgender){returngender.getName();}}上面只是最简单的实体映射处理，下面介绍一些高级用法
1.List 转换
属性映射基于上面的mapping配置
@MapperpublicinterfaceStudentMapper{StudentMapperINSTANCE=Mappers.getMapper(StudentMapper.class);@Mapping(source="gender.name",target="gender")@Mapping(source="birthday",target="birthday",dateFormat="yyyy-MM-ddHH:mm:ss")StudentVOstudent2StudentVO(Studentstudent);List<StudentVO>students2StudentVOs(List<Student>studentList);}publicstaticvoidmain(String[]args){Studentstudent=Student.builder().name("小明").age(6).gender(GenderEnum.Male).height(121.1).birthday(newDate()).build();List<Student>list=newArrayList<>();list.add(student);List<StudentVO>result=StudentMapper.INSTANCE.students2StudentVOs(list);System.out.println(result);}2.多对象转换到一个对象
@Data@Builder@AllArgsConstructor@NoArgsConstructorpublicclassStudent{privateStringname;privateintage;privateGenderEnumgender;privateDoubleheight;privateDatebirthday;}@Data@AllArgsConstructor@Builder@NoArgsConstructorpublicclassCourse{privateStringcourseName;privateintsortNo;privatelongid;}@Data@Builder@AllArgsConstructor@NoArgsConstructorpublicclassStudentVO{privateStringname;privateintage;privateStringgender;privateDoubleheight;privateStringbirthday;privateStringcourse;}@MapperpublicinterfaceStudentMapper{StudentMapperINSTANCE=Mappers.getMapper(StudentMapper.class);@Mapping(source="student.gender.name",target="gender")@Mapping(source="student.birthday",target="birthday",dateFormat="yyyy-MM-ddHH:mm:ss")@Mapping(source="course.courseName",target="course")StudentVOstudentAndCourse2StudentVO(Studentstudent,Coursecourse);}publicclassTest{publicstaticvoidmain(String[]args){Studentstudent=Student.builder().name("小明").age(6).gender(GenderEnum.Male).height(121.1).birthday(newDate()).build();Coursecourse=Course.builder().id(1L).courseName("语文").build();StudentVOstudentVO=StudentMapper.INSTANCE.studentAndCourse2StudentVO(student,course);System.out.println(studentVO);}}3.默认值
@MapperpublicinterfaceStudentMapper{StudentMapperINSTANCE=Mappers.getMapper(StudentMapper.class);@Mapping(source="student.gender.name",target="gender")@Mapping(source="student.birthday",target="birthday",dateFormat="yyyy-MM-ddHH:mm:ss")@Mapping(source="course.courseName",target="course")@Mapping(target="name",source="student.name",defaultValue="张三")StudentVOstudentAndCourse2StudentVO(Studentstudent,Coursecourse);}有热门推荐????给IDEA换个酷炫的主题，这个有点哇塞啊！一条 SQL 引发的事故，同事直接被开除！！Mybatis 使用的 9 种设计模式，真是太有用了Java数组转List的三种方式及对比推荐一款日志切割神器！我常用~使用 Stream API 高逼格 优化 Java 代码！Spring MVC请求处理过程不是两张流程图就能讲清楚的撸一个简易聊天室，不信你学不会实时消息推送（附源码）Spring Boot 打包不同环境配置与 Shell 脚本部署最后分享一套微服务电商项目教程（资料笔记+视频）：点击阅读全文获取面试资料+项目实战资料（电商/聚合支付）点击阅读原文，前往上面微服务电商教程文档页