遇到MapStruct后，再也不手写PO，DTO，VO对象之间的转换了

欢迎大家来到IT世界,在知识的湖畔探索吧!

欢迎大家来到IT世界,在知识的湖畔探索吧!

介绍

在工作中，我们经常要进行各种对象之间的转换。

PO：persistent object 持久对象，对应数据库中的一条记录

VO：view object 表现层对象，最终返回给前端的对象

DTO：data transfer object数据传输对象，如dubbo服务之间传输的对象

如果这些对象的属性名相同还好，可以用如下工具类赋值

Spring BeanUtils

Cglib BeanCopier

避免使用Apache BeanUtils，性能较差

如果属性名不同呢？如果是将多个PO对象合并成一个VO对象呢？好在有MapStruct神器，可以帮助我们快速转换

在pom文件中加入如下依赖即可

<dependency> <groupId>org.mapstruct</groupId> <artifactId>mapstruct-jdk8</artifactId> <version>1.2.0.CR1</version> </dependency> <dependency> <groupId>org.mapstruct</groupId> <artifactId>mapstruct-processor</artifactId> <version>1.2.0.CR1</version> <scope>provided</scope> </dependency>

欢迎大家来到IT世界,在知识的湖畔探索吧!

对象互转

欢迎大家来到IT世界,在知识的湖畔探索吧!@Data @Builder public class StudentPO { private Integer id; private String name; private Integer age; private String className; }

@Data public class StudentVO { private Integer id; private String studentName; private Integer studentAge; private String schoolName; }

欢迎大家来到IT世界,在知识的湖畔探索吧!@Mapper public interface StudentMapper { StudentMapper INSTANCE = Mappers.getMapper(StudentMapper.class); @Mappings({ @Mapping(source = "name", target = "studentName"), @Mapping(source = "age", target = "studentAge") }) StudentVO po2Vo(StudentPO studentPO); }

1. 新建一个Mapper接口，上面加上@Mapper注解

2. 新建一个成员变量INSTANCE

3. 用@Mapping注解指定映射关系，名字相同的就不用再指定了，会自动映射

测试效果如下，名字不同且没有指定映射关系的会被设置为null

@Test public void studentPo2Vo() { StudentPO studentPO = StudentPO.builder().id(10).name("test") .age(24).className("教室名").build(); StudentVO studentVO = StudentMapper.INSTANCE.po2Vo(studentPO); // StudentVO(id=10, studentName=test, studentAge=24, schoolName=null) System.out.println(studentVO); }

List互转

欢迎大家来到IT世界,在知识的湖畔探索吧!@Mapper public interface StudentMapper { StudentMapper INSTANCE = Mappers.getMapper(StudentMapper.class); @Mappings({ @Mapping(source = "name", target = "studentName"), @Mapping(source = "age", target = "studentAge") }) StudentVO po2Vo(StudentPO studentPO); List<StudentVO> poList2VoList(List<StudentPO> studentPO); }

List类型互转的映射规则会用单个对象的映射规则，看测试效果

@Test public void poList2VoList() { List<StudentPO> studentPOList = new ArrayList<>(); for (int i = 1; i <= 2; i++) { StudentPO studentPO = StudentPO.builder().id(i).name(String.valueOf(i)).age(i).build(); studentPOList.add(studentPO); } List<StudentVO> studentVOList = StudentMapper.INSTANCE.poList2VoList(studentPOList); // [StudentVO(id=1, studentName=1, studentAge=1, schoolName=null), // StudentVO(id=2, studentName=2, studentAge=2, schoolName=null)] System.out.println(studentVOList); }

多个对象映射一个对象

我们用SchoolPO和StudentPO来映射SchoolStudentVO

欢迎大家来到IT世界,在知识的湖畔探索吧!@Data @Builder public class SchoolPO { private String name; private String location; }

@Data @Builder public class StudentPO { private Integer id; private String name; private Integer age; private String className; }

欢迎大家来到IT世界,在知识的湖畔探索吧!@Data public class SchoolStudentVO { private String schoolName; private String studentName; }

@Mapper public interface StudentMapper { @Mappings({ @Mapping(source = "schoolPO.name", target = "schoolName"), @Mapping(source = "studentPO.name", target = "studentName") }) SchoolStudentVO mergeVo(SchoolPO schoolPO, StudentPO studentPO); }

测试例子如下

欢迎大家来到IT世界,在知识的湖畔探索吧!@Test public void mergeVo() { SchoolPO schoolPO = SchoolPO.builder().name("学校名字").build(); StudentPO studentPO = StudentPO.builder().name("学生名字").build(); SchoolStudentVO schoolStudentVO = StudentMapper.INSTANCE.mergeVo(schoolPO, studentPO); // SchoolStudentVO(schoolName=学校名字, studentName=学生名字) System.out.println(schoolStudentVO); }

当然还有其他的骚操作，这里就简单介绍一个比较实用的技巧，有兴趣的可以看官方的example

https://github.com/mapstruct/mapstruct-examples