map判断是否是最后一个元素（遇到MapStruct后再也不手写PO）
map判断是否是最后一个元素（遇到MapStruct后再也不手写PO）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避免使用Apache BeanUtils，性能较差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 BeanUtilsCglib BeanCopier
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>对象互转
@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;
}
@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);
}
- 新建一个Mapper接口，上面加上@Mapper注解
- 新建一个成员变量INSTANCE
- 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
@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
@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;
}
@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
@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
