遇到MapStruct後，再也不手寫PO，DTO，VO對象之間的轉換了

介紹

在工作中，我們經常要進行各種對象之間的轉換。

PO：persistent object 持久對象，對應數據庫中的一條記錄

VO：view object 表現層對象，最終返回給前端的對象

DTO：data transfer object數據傳輸對象，如dubbo服務之間傳輸的對象

如果這些對象的屬性名相同還好，可以用如下工具類賦值

Spring BeanUtils

Cglib BeanCopier

避免使用Apache BeanUtils，性能較差

如果屬性名不同呢？如果是將多個PO對象合併成一個VO對象呢？好在有MapStruct神器，可以幫助我們快速轉換

在pom文件中加入如下依賴即可

<code>
<
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
>
/<code>

對象互轉

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

<code> 
public
 
class
 StudentVO {
    
private
 Integer id;
    
private
 
String
 studentName;
    
private
 Integer studentAge;
    
private
 
String
 schoolName;
}/<code>

<code> 
public
 
interface
 
StudentMapper
 
{
    StudentMapper INSTANCE = Mappers.getMapper(StudentMapper
.
class
)
;
     ({
             (source = 
"name"
, target = 
"studentName"
),
             (source = 
"age"
, target = 
"studentAge"
)
    })
     
StudentVO 
po2Vo
(StudentPO studentPO)
;
}/<code>

1. 新建一個Mapper接口，上面加上@Mapper註解

2. 新建一個成員變量INSTANCE

3. 用@Mapping註解指定映射關係，名字相同的就不用再指定了，會自動映射

測試效果如下，名字不同且沒有指定映射關係的會被設置為null

<code>@
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);
     
    System.
out
.println(studentVO);
}/<code>

List互轉

<code> 
public
 
interface
 
StudentMapper
 
{
    StudentMapper INSTANCE = Mappers.getMapper(StudentMapper
.
class
)
;
     ({
             (source = 
"name"
, target = 
"studentName"
),
             (source = 
"age"
, target = 
"studentAge"
)
    })
    
StudentVO 
po2Vo
(StudentPO studentPO)
;
    
List 
poList2VoList
(List studentPO)
;
}/<code>

List類型互轉的映射規則會用單個對象的映射規則，看測試效果

<code>@
Test
public
 
void
 
poList2VoList 
(
)
 {
    List 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 studentVOList = StudentMapper.INSTANCE.poList2VoList(studentPOList);
     
     
    System.
out
.println(studentVOList);
}/<code>

多個對象映射一個對象

我們用SchoolPO和StudentPO來映射SchoolStudentVO

<code>
@Data
@Builder
public class SchoolPO {
    
private
 
String
 
name
;
    
private
 
String
 
location
;
}/<code>

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

<code> 
public
 
class
 SchoolStudentVO {
    
private
 
String
 schoolName;
    
private
 
String
 studentName;
}/<code>

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

測試例子如下

<code>@
Test
public
 
void
 
mergeVo
(
)
 {
    SchoolPO schoolPO = SchoolPO.builder().name(
"學校名字"
).build();
    StudentPO studentPO = StudentPO.builder().name(
"學生名字"
).build();
    SchoolStudentVO schoolStudentVO = StudentMapper.INSTANCE.mergeVo(schoolPO, studentPO);
     
    System.
out
.println(schoolStudentVO);
}/<code>

當然還有其他的騷操作，這裡就簡單介紹一個比較實用的技巧，有興趣的可以看官方的example

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

專欄

Java面試通關100問

作者：Java識堂

19.9幣

285人已購

查看