当前位置：网站首页>After encountering MapStruct, the conversion between PO, DTO and VO objects is no longer handwritten

After encountering MapStruct, the conversion between PO, DTO and VO objects is no longer handwritten

2022-08-04 20:25:00 【51CTO】

遇到MapStruct后,no more handwritingPO,DTO,VOconversion between objects_ide

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
       
       >
      
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.

对象互转

       
       @Data
       
       @Builder
       
       public 
       
       class 
       
       StudentPO {
       
       private 
       
       Integer 
       
       id;
       
       private 
       
       String 
       
       name;
       
       private 
       
       Integer 
       
       age;
       
       private 
       
       String 
       
       className;
       
}
      
1.
2.
3.
4.
5.
6.
7.
8.
9.

       
       @Data
       
       public 
       
       class 
       
       StudentVO {
       
       private 
       
       Integer 
       
       id;
       
       private 
       
       String 
       
       studentName;
       
       private 
       
       Integer 
       
       studentAge;
       
       private 
       
       String 
       
       schoolName;
       
}
      
1.
2.
3.
4.
5.
6.
7.
8.

       
       @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.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.

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);
       
}
      
1.
2.
3.
4.
5.
6.
7.
8.

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);
       
}
      
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.

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);
       
}
      
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.

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;
       
}
      
1.
2.
3.
4.
5.
6.
7.

       
       @Data
       
       @Builder
       
       public 
       
       class 
       
       StudentPO {
       
       private 
       
       Integer 
       
       id;
       
       private 
       
       String 
       
       name;
       
       private 
       
       Integer 
       
       age;
       
       private 
       
       String 
       
       className;
       
}
      
1.
2.
3.
4.
5.
6.
7.
8.
9.

       
       @Data
       
       public 
       
       class 
       
       SchoolStudentVO {
       
       private 
       
       String 
       
       schoolName;
       
       private 
       
       String 
       
       studentName;
       
}
      
1.
2.
3.
4.
5.
6.

       
       @Mapper
       
       public 
       
       interface 
       
       StudentMapper {
       
       @Mappings({
       
       @Mapping(
       
       source 
       
       = 
       
       "schoolPO.name", 
       
       target 
       
       = 
       
       "schoolName"),
       
       @Mapping(
       
       source 
       
       = 
       
       "studentPO.name", 
       
       target 
       
       = 
       
       "studentName")
       
    })
       
       SchoolStudentVO 
       
       mergeVo(
       
       SchoolPO 
       
       schoolPO, 
       
       StudentPO 
       
       studentPO);
       
}
      
1.
2.
3.
4.
5.
6.
7.
8.
9.

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);
       
}
      
1.
2.
3.
4.
5.
6.
7.
8.

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

Specify the method when converting

       
       @Data
       
       @Builder
       
       public 
       
       class 
       
       PersonVO {
       
       private 
       
       int 
       
       age;
       
       private 
       
       GenderEnum 
       
       gender;
       
}
      
1.
2.
3.
4.
5.
6.
7.

       
       @Getter
       
       @AllArgsConstructor
       
       public 
       
       enum 
       
       GenderEnum {
       
       FEMALE(
       
       0, 
       
       "女性"),
       
       MALE(
       
       1, 
       
       "男性");
       
       private 
       
       int 
       
       value;
       
       private 
       
       String 
       
       name;
       
}
      
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.

       
       @Data
       
       public 
       
       class 
       
       PersonPO {
       
       private 
       
       int 
       
       age;
       
       private 
       
       int 
       
       gender;
       
}
      
1.
2.
3.
4.
5.
6.

当我们想把PersonVO转换为PersonPO,PersonPO中的gender是一个枚举,PersonVO中的gender是一个int类型,How to convert enum to enumvalue值呢？

在@Mapping注解中通过qualifiedByNameThe attribute specifies the method of conversion

       
       @Mapper
       
       public 
       
       interface 
       
       StudentMapper {
       
       StudentMapper 
       
       INSTANCE 
       
       = 
       
       Mappers.
       
       getMapper(
       
       StudentMapper.
       
       class);
       
       @Mappings({
       
       @Mapping(
       
       source 
       
       = 
       
       "gender", 
       
       target 
       
       = 
       
       "gender", 
       
       qualifiedByName 
       
       = 
       
       "convertGender"),
       
    })
       
       PersonPO 
       
       vo2Po(
       
       PersonVO 
       
       personVO);
       
       @Named(
       
       "convertGender")
       
       default 
       
       Integer 
       
       convertTargetType(
       
       GenderEnum 
       
       genderEnum) {
       
       return 
       
       genderEnum.
       
       getValue();
       
    }
       
}
      
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.

测试类如下

       
       @Test
       
       public 
       
       void 
       
       specifyMethod() {
       
       PersonVO 
       
       personVO 
       
       = 
       
       PersonVO.
       
       builder().
       
       age(
       
       10).
       
       gender(
       
       GenderEnum.
       
       MALE).
       
       build();
       
       PersonPO 
       
       personPO 
       
       = 
       
       StudentMapper.
       
       INSTANCE.
       
       vo2Po(
       
       personVO);
       
       // PersonPO(age=10, gender=1)
       
       System.
       
       out.
       
       println(
       
       personPO);
       
}
      
1.
2.
3.
4.
5.
6.
7.

实现原理

MapStruct帮你对接口生成了一个实现类,下面就是生成的实现类,从class文件夹中可以看到

       
       public 
       
       class 
       
       StudentMapperImpl 
       
       implements 
       
       StudentMapper {
       
       @Override
       
       public 
       
       StudentVO 
       
       po2Vo(
       
       StudentPO 
       
       studentPO) {
       
       if ( 
       
       studentPO 
       
       == 
       
       null ) {
       
       return 
       
       null;
       
        }
       
       StudentVO 
       
       studentVO 
       
       = 
       
       new 
       
       StudentVO();
       
       studentVO.
       
       setStudentAge( 
       
       studentPO.
       
       getAge() );
       
       studentVO.
       
       setStudentName( 
       
       studentPO.
       
       getName() );
       
       studentVO.
       
       setId( 
       
       studentPO.
       
       getId() );
       
       return 
       
       studentVO;
       
    }
       
       @Override
       
       public 
       
       List
       
       <
       
       StudentVO
       
       > 
       
       poList2VoList(
       
       List
       
       <
       
       StudentPO
       
       > 
       
       studentPO) {
       
       if ( 
       
       studentPO 
       
       == 
       
       null ) {
       
       return 
       
       null;
       
        }
       
       List
       
       <
       
       StudentVO
       
       > 
       
       list 
       
       = 
       
       new 
       
       ArrayList
       
       <
       
       StudentVO
       
       >( 
       
       studentPO.
       
       size() );
       
       for ( 
       
       StudentPO 
       
       studentPO1 : 
       
       studentPO ) {
       
       list.
       
       add( 
       
       po2Vo( 
       
       studentPO1 ) );
       
        }
       
       return 
       
       list;
       
    }
       
       @Override
       
       public 
       
       SchoolStudentVO 
       
       mergeVo(
       
       SchoolPO 
       
       schoolPO, 
       
       StudentPO 
       
       studentPO) {
       
       if ( 
       
       schoolPO 
       
       == 
       
       null 
       
       && 
       
       studentPO 
       
       == 
       
       null ) {
       
       return 
       
       null;
       
        }
       
       SchoolStudentVO 
       
       schoolStudentVO 
       
       = 
       
       new 
       
       SchoolStudentVO();
       
       if ( 
       
       schoolPO 
       
       != 
       
       null ) {
       
       schoolStudentVO.
       
       setSchoolName( 
       
       schoolPO.
       
       getName() );
       
        }
       
       if ( 
       
       studentPO 
       
       != 
       
       null ) {
       
       schoolStudentVO.
       
       setStudentName( 
       
       studentPO.
       
       getName() );
       
        }
       
       return 
       
       schoolStudentVO;
       
    }
       
       @Override
       
       public 
       
       PersonPO 
       
       vo2Po(
       
       PersonVO 
       
       personVO) {
       
       if ( 
       
       personVO 
       
       == 
       
       null ) {
       
       return 
       
       null;
       
        }
       
       PersonPO 
       
       personPO 
       
       = 
       
       new 
       
       PersonPO();
       
       personPO.
       
       setGender( 
       
       convertTargetType( 
       
       personVO.
       
       getGender() ) );
       
       personPO.
       
       setAge( 
       
       personVO.
       
       getAge() );
       
       return 
       
       personPO;
       
    }
       
}
      
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
38.
39.
40.
41.
42.
43.
44.
45.
46.
47.
48.
49.
50.
51.
52.
53.
54.
55.
56.
57.
58.
59.
60.
61.
62.
63.
64.
65.
66.
67.
68.
69.
70.
71.
72.
73.
74.
75.
76.
77.
78.
79.
80.
81.
82.
83.