實(shí)體映射最強(qiáng)工具類：MapStruct 真香！

來(lái)源：blog.csdn.net/qq122516902

首先來(lái)了解一下DTO，DTO簡(jiǎn)單的理解就是做數(shù)據(jù)傳輸對(duì)象的，類似于VO，但是VO用于傳輸?shù)角岸恕＃▇~）

1.MapStruct是用來(lái)做什么的？

現(xiàn)在有這么個(gè)場(chǎng)景，從數(shù)據(jù)庫(kù)查詢出來(lái)了一個(gè)user對(duì)象（包含id，用戶名，密碼，手機(jī)號(hào)，郵箱，角色這些字段）和一個(gè)對(duì)應(yīng)的角色對(duì)象role（包含id，角色名，角色描述這些字段），現(xiàn)在在controller需要用到user對(duì)象的id，用戶名，和角色對(duì)象的角色名三個(gè)屬性。

一種方式是直接把兩個(gè)對(duì)象傳遞到controller層，但是這樣會(huì)多出很多沒(méi)用的屬性。更通用的方式是需要用到的屬性封裝成一個(gè)類(DTO)，通過(guò)傳輸這個(gè)類的實(shí)例來(lái)完成數(shù)據(jù)傳輸。

User.java

@AllArgsConstructor??
@Data??
public?class?User?{??
????private?Long?id;??
????private?String?username;??
????private?String?password;??
????private?String?phoneNum;??
????private?String?email;??
????private?Role?role;??
}??

Role.java

@AllArgsConstructor??
@Data??
public?class?Role?{??
????private?Long?id;??
????private?String?roleName;??
????private?String?description;??
}??

UserRoleDto.java，這個(gè)類就是封裝的類

@Data??
public?class?UserRoleDto?{??
????/**??
?????*?用戶id??
?????*/??
????private?Long?userId;??
????/**??
?????*?用戶名??
?????*/??
????private?String?name;??
????/**??
?????*?角色名??
?????*/??
????private?String?roleName;??
}??

測(cè)試類，模擬將user對(duì)象轉(zhuǎn)換成UserRoleDto對(duì)象

public?class?MainTest?{??
????User?user?=?null;??
??
????/**??
?????*?模擬從數(shù)據(jù)庫(kù)中查出user對(duì)象??
?????*/??
????@Before??
????public?void?before()?{??
???????Role?role??=?new?Role(2L,?"administrator",?"超級(jí)管理員");??
???????user??=?new?User(1L,?"zhangsan",?"12345",?"17677778888",?"[email protected]",?role);??
????}??
??
????/**??
?????*?模擬把user對(duì)象轉(zhuǎn)換成UserRoleDto對(duì)象??
?????*/??
????@Test??
????public?void?test1()?{??
????????UserRoleDto?userRoleDto?=?new?UserRoleDto();??
????????userRoleDto.setUserId(user.getId());??
????????userRoleDto.setName(user.getUsername());??
????????userRoleDto.setRoleName(user.getRole().getRoleName());??
????????System.out.println(userRoleDto);??
????}??
}??

從上面代碼可以看出，通過(guò)getter、setter的方式把一個(gè)對(duì)象屬性值復(fù)制到另一個(gè)對(duì)象中去還是很麻煩的，尤其是當(dāng)屬性過(guò)多的時(shí)候。而MapStruct就是用于解決這種問(wèn)題的。

2.使用MapStruct解決上述問(wèn)題

這里我們沿用User.java、Role.java、UserRoleDto.java。

新建一個(gè)UserRoleMapper.java，這個(gè)來(lái)用來(lái)定義User.java、Role.java和UserRoleDto.java之間屬性對(duì)應(yīng)規(guī)則：

UserRoleMapper.java

import?org.mapstruct.Mapper;??
import?org.mapstruct.Mapping;??
import?org.mapstruct.Mappings;??
import?org.mapstruct.factory.Mappers;??
??
/**??
?*?@Mapper?定義這是一個(gè)MapStruct對(duì)象屬性轉(zhuǎn)換接口，在這個(gè)類里面規(guī)定轉(zhuǎn)換規(guī)則??
?*??????????在項(xiàng)目構(gòu)建時(shí)，會(huì)自動(dòng)生成改接口的實(shí)現(xiàn)類，這個(gè)實(shí)現(xiàn)類將實(shí)現(xiàn)對(duì)象屬性值復(fù)制??
?*/??
@Mapper??
public?interface?UserRoleMapper?{??
??
????/**??
?????*?獲取該類自動(dòng)生成的實(shí)現(xiàn)類的實(shí)例??
?????*?接口中的屬性都是?public?static?final?的?方法都是public?abstract的??
?????*/??
????UserRoleMapper?INSTANCES?=?Mappers.getMapper(UserRoleMapper.class);??
??
????/**??
?????*?這個(gè)方法就是用于實(shí)現(xiàn)對(duì)象屬性復(fù)制的方法??
?????*??
?????*?@Mapping?用來(lái)定義屬性復(fù)制規(guī)則?source?指定源對(duì)象屬性?target指定目標(biāo)對(duì)象屬性??
?????*??
?????*?@param?user?這個(gè)參數(shù)就是源對(duì)象，也就是需要被復(fù)制的對(duì)象??
?????*?@return?返回的是目標(biāo)對(duì)象，就是最終的結(jié)果對(duì)象??
?????*/??
????@Mappings({??
????????????@Mapping(source?=?"id",?target?=?"userId"),??
????????????@Mapping(source?=?"username",?target?=?"name"),??
????????????@Mapping(source?=?"role.roleName",?target?=?"roleName")??
????})??
????UserRoleDto?toUserRoleDto(User?user);??
??
}??

在測(cè)試類中測(cè)試：

通過(guò)上面的例子可以看出，使用MapStruct方便許多。

3.添加默認(rèn)方法

添加默認(rèn)方法是為了這個(gè)類（接口）不只是為了做數(shù)據(jù)轉(zhuǎn)換用的，也可以做一些其他的事。

import?org.mapstruct.Mapper;??
import?org.mapstruct.Mapping;??
import?org.mapstruct.Mappings;??
import?org.mapstruct.factory.Mappers;??
??
/**??
?*?@Mapper?定義這是一個(gè)MapStruct對(duì)象屬性轉(zhuǎn)換接口，在這個(gè)類里面規(guī)定轉(zhuǎn)換規(guī)則??
?*??????????在項(xiàng)目構(gòu)建時(shí)，會(huì)自動(dòng)生成改接口的實(shí)現(xiàn)類，這個(gè)實(shí)現(xiàn)類將實(shí)現(xiàn)對(duì)象屬性值復(fù)制??
?*/??
@Mapper??
public?interface?UserRoleMapper?{??
??
????/**??
?????*?獲取該類自動(dòng)生成的實(shí)現(xiàn)類的實(shí)例??
?????*?接口中的屬性都是?public?static?final?的?方法都是public?abstract的??
?????*/??
????UserRoleMapper?INSTANCES?=?Mappers.getMapper(UserRoleMapper.class);??
??
????/**??
?????*?這個(gè)方法就是用于實(shí)現(xiàn)對(duì)象屬性復(fù)制的方法??
?????*??
?????*?@Mapping?用來(lái)定義屬性復(fù)制規(guī)則?source?指定源對(duì)象屬性?target指定目標(biāo)對(duì)象屬性??
?????*??
?????*?@param?user?這個(gè)參數(shù)就是源對(duì)象，也就是需要被復(fù)制的對(duì)象??
?????*?@return?返回的是目標(biāo)對(duì)象，就是最終的結(jié)果對(duì)象??
?????*/??
????@Mappings({??
????????????@Mapping(source?=?"id",?target?=?"userId"),??
????????????@Mapping(source?=?"username",?target?=?"name"),??
????????????@Mapping(source?=?"role.roleName",?target?=?"roleName")??
????})??
????UserRoleDto?toUserRoleDto(User?user);??
??
????/**??
?????*?提供默認(rèn)方法，方法自己定義，這個(gè)方法是我隨便寫(xiě)的，不是要按照這個(gè)格式來(lái)的??
?????*?@return??
?????*/??
????default?UserRoleDto?defaultConvert()?{??
????????UserRoleDto?userRoleDto?=?new?UserRoleDto();??
????????userRoleDto.setUserId(0L);??
????????userRoleDto.setName("None");??
????????userRoleDto.setRoleName("None");??
????????return?userRoleDto;??
????}??
??
}??

測(cè)試代碼：

@Test??
public?void?test3()?{??
????UserRoleMapper?userRoleMapperInstances?=?UserRoleMapper.INSTANCES;??
????UserRoleDto?userRoleDto?=?userRoleMapperInstances.defaultConvert();??
????System.out.println(userRoleDto);??
}??

4. 可以使用abstract class來(lái)代替接口

mapper可以用接口來(lái)實(shí)現(xiàn)，也可以完全由抽象來(lái)完全代替

import?org.mapstruct.Mapper;??
import?org.mapstruct.Mapping;??
import?org.mapstruct.Mappings;??
import?org.mapstruct.factory.Mappers;??
??
/**??
?*?@Mapper?定義這是一個(gè)MapStruct對(duì)象屬性轉(zhuǎn)換接口，在這個(gè)類里面規(guī)定轉(zhuǎn)換規(guī)則??
?*??????????在項(xiàng)目構(gòu)建時(shí)，會(huì)自動(dòng)生成改接口的實(shí)現(xiàn)類，這個(gè)實(shí)現(xiàn)類將實(shí)現(xiàn)對(duì)象屬性值復(fù)制??
?*/??
@Mapper??
public?abstract?class?UserRoleMapper?{??
??
????/**??
?????*?獲取該類自動(dòng)生成的實(shí)現(xiàn)類的實(shí)例??
?????*?接口中的屬性都是?public?static?final?的?方法都是public?abstract的??
?????*/??
????public?static?final?UserRoleMapper?INSTANCES?=?Mappers.getMapper(UserRoleMapper.class);??
??
????/**??
?????*?這個(gè)方法就是用于實(shí)現(xiàn)對(duì)象屬性復(fù)制的方法??
?????*??
?????*?@Mapping?用來(lái)定義屬性復(fù)制規(guī)則?source?指定源對(duì)象屬性?target指定目標(biāo)對(duì)象屬性??
?????*??
?????*?@param?user?這個(gè)參數(shù)就是源對(duì)象，也就是需要被復(fù)制的對(duì)象??
?????*?@return?返回的是目標(biāo)對(duì)象，就是最終的結(jié)果對(duì)象??
?????*/??
????@Mappings({??
????????????@Mapping(source?=?"id",?target?=?"userId"),??
????????????@Mapping(source?=?"username",?target?=?"name"),??
????????????@Mapping(source?=?"role.roleName",?target?=?"roleName")??
????})??
????public?abstract?UserRoleDto?toUserRoleDto(User?user);??
??
????/**??
?????*?提供默認(rèn)方法，方法自己定義，這個(gè)方法是我隨便寫(xiě)的，不是要按照這個(gè)格式來(lái)的??
?????*?@return??
?????*/??
????UserRoleDto?defaultConvert()?{??
????????UserRoleDto?userRoleDto?=?new?UserRoleDto();??
????????userRoleDto.setUserId(0L);??
????????userRoleDto.setName("None");??
????????userRoleDto.setRoleName("None");??
????????return?userRoleDto;??
????}??
??
}??

5.可以使用多個(gè)參數(shù)

可以綁定多個(gè)對(duì)象的屬性值到目標(biāo)對(duì)象中：

package?com.mapstruct.demo;??
??
import?org.mapstruct.Mapper;??
import?org.mapstruct.Mapping;??
import?org.mapstruct.Mappings;??
import?org.mapstruct.factory.Mappers;??
??
/**??
?*?@Mapper?定義這是一個(gè)MapStruct對(duì)象屬性轉(zhuǎn)換接口，在這個(gè)類里面規(guī)定轉(zhuǎn)換規(guī)則??
?*??????????在項(xiàng)目構(gòu)建時(shí)，會(huì)自動(dòng)生成改接口的實(shí)現(xiàn)類，這個(gè)實(shí)現(xiàn)類將實(shí)現(xiàn)對(duì)象屬性值復(fù)制??
?*/??
@Mapper??
public?interface?UserRoleMapper?{??
??
????/**??
?????*?獲取該類自動(dòng)生成的實(shí)現(xiàn)類的實(shí)例??
?????*?接口中的屬性都是?public?static?final?的?方法都是public?abstract的??
?????*/??
????UserRoleMapper?INSTANCES?=?Mappers.getMapper(UserRoleMapper.class);??
??
????/**??
?????*?這個(gè)方法就是用于實(shí)現(xiàn)對(duì)象屬性復(fù)制的方法??
?????*??
?????*?@Mapping?用來(lái)定義屬性復(fù)制規(guī)則?source?指定源對(duì)象屬性?target指定目標(biāo)對(duì)象屬性??
?????*??
?????*?@param?user?這個(gè)參數(shù)就是源對(duì)象，也就是需要被復(fù)制的對(duì)象??
?????*?@return?返回的是目標(biāo)對(duì)象，就是最終的結(jié)果對(duì)象??
?????*/??
????@Mappings({??
????????????@Mapping(source?=?"id",?target?=?"userId"),??
????????????@Mapping(source?=?"username",?target?=?"name"),??
????????????@Mapping(source?=?"role.roleName",?target?=?"roleName")??
????})??
????UserRoleDto?toUserRoleDto(User?user);??
??
????/**??
?????*?多個(gè)參數(shù)中的值綁定???
?????*?@param?user?源1??
?????*?@param?role?源2??
?????*?@return?從源1、2中提取出的結(jié)果??
?????*/??
????@Mappings({??
????????????@Mapping(source?=?"user.id",?target?=?"userId"),?//?把user中的id綁定到目標(biāo)對(duì)象的userId屬性中??
????????????@Mapping(source?=?"user.username",?target?=?"name"),?//?把user中的username綁定到目標(biāo)對(duì)象的name屬性中??
????????????@Mapping(source?=?"role.roleName",?target?=?"roleName")?//?把role對(duì)象的roleName屬性值綁定到目標(biāo)對(duì)象的roleName中??
????})??
????UserRoleDto?toUserRoleDto(User?user,?Role?role);??

對(duì)比兩個(gè)方法~

5.直接使用參數(shù)作為屬性值

package?com.mapstruct.demo;??
??
import?org.mapstruct.Mapper;??
import?org.mapstruct.Mapping;??
import?org.mapstruct.Mappings;??
import?org.mapstruct.factory.Mappers;??
??
/**??
?*?@Mapper?定義這是一個(gè)MapStruct對(duì)象屬性轉(zhuǎn)換接口，在這個(gè)類里面規(guī)定轉(zhuǎn)換規(guī)則??
?*??????????在項(xiàng)目構(gòu)建時(shí)，會(huì)自動(dòng)生成改接口的實(shí)現(xiàn)類，這個(gè)實(shí)現(xiàn)類將實(shí)現(xiàn)對(duì)象屬性值復(fù)制??
?*/??
@Mapper??
public?interface?UserRoleMapper?{??
??
????/**??
?????*?獲取該類自動(dòng)生成的實(shí)現(xiàn)類的實(shí)例??
?????*?接口中的屬性都是?public?static?final?的?方法都是public?abstract的??
?????*/??
????UserRoleMapper?INSTANCES?=?Mappers.getMapper(UserRoleMapper.class);??
??
????/**??
?????*?直接使用參數(shù)作為值??
?????*?@param?user??
?????*?@param?myRoleName??
?????*?@return??
?????*/??
????@Mappings({??
????????????@Mapping(source?=?"user.id",?target?=?"userId"),?//?把user中的id綁定到目標(biāo)對(duì)象的userId屬性中??
????????????@Mapping(source?=?"user.username",?target?=?"name"),?//?把user中的username綁定到目標(biāo)對(duì)象的name屬性中??
????????????@Mapping(source?=?"myRoleName",?target?=?"roleName")?//?把role對(duì)象的roleName屬性值綁定到目標(biāo)對(duì)象的roleName中??
????})??
????UserRoleDto?useParameter(User?user,?String?myRoleName);??
??
}??

測(cè)試類：

public?class?Test1?{??
????Role?role?=?null;??
????User?user?=?null;??
??
????@Before??
????public?void?before()?{??
????????role?=?new?Role(2L,?"administrator",?"超級(jí)管理員");??
????????user?=?new?User(1L,?"zhangsan",?"12345",?"17677778888",?"[email protected]",?role);??
????}??
????@Test??
????public?void?test1()?{??
????????UserRoleMapper?instances?=?UserRoleMapper.INSTANCES;??
????????UserRoleDto?userRoleDto?=?instances.useParameter(user,?"myUserRole");??
????????System.out.println(userRoleDto);??
????}??
}??

6.更新對(duì)象屬性

在之前的例子中UserRoleDto useParameter(User user, String myRoleName);都是通過(guò)類似上面的方法來(lái)生成一個(gè)對(duì)象。而MapStruct提供了另外一種方式來(lái)更新一個(gè)對(duì)象中的屬性。@MappingTarget

public?interface?UserRoleMapper1?{??
??
????UserRoleMapper1?INSTANCES?=?Mappers.getMapper(UserRoleMapper1.class);??
??
????@Mappings({??
????????????@Mapping(source?=?"userId",?target?=?"id"),??
????????????@Mapping(source?=?"name",?target?=?"username"),??
????????????@Mapping(source?=?"roleName",?target?=?"role.roleName")??
????})??
????void?updateDto(UserRoleDto?userRoleDto,?@MappingTarget?User?user);??
??
??
????@Mappings({??
????????????@Mapping(source?=?"id",?target?=?"userId"),??
????????????@Mapping(source?=?"username",?target?=?"name"),??
????????????@Mapping(source?=?"role.roleName",?target?=?"roleName")??
????})??
????void?update(User?user,?@MappingTarget?UserRoleDto?userRoleDto);??
??
}??

通過(guò)@MappingTarget來(lái)指定目標(biāo)類是誰(shuí)（誰(shuí)的屬性需要被更新）。@Mapping還是用來(lái)定義屬性對(duì)應(yīng)規(guī)則。

以此為例說(shuō)明：

@Mappings({??
????????????@Mapping(source?=?"id",?target?=?"userId"),??
????????????@Mapping(source?=?"username",?target?=?"name"),??
????????????@Mapping(source?=?"role.roleName",?target?=?"roleName")??
????})??
????void?update(User?user,?@MappingTarget?UserRoleDto?userRoleDto);??

@MappingTarget標(biāo)注的類UserRoleDto 為目標(biāo)類，user類為源類，調(diào)用此方法，會(huì)把源類中的屬性更新到目標(biāo)類中。更新規(guī)則還是由@Mapping指定。

7.沒(méi)有g(shù)etter/setter也能賦值

對(duì)于沒(méi)有g(shù)etter/setter的屬性也能實(shí)現(xiàn)賦值操作

public?class?Customer?{??
??
????private?Long?id;??
????private?String?name;??
??
????//getters?and?setter?omitted?for?brevity??
}??
??
public?class?CustomerDto?{??
??
????public?Long?id;??
????public?String?customerName;??
}??
??
@Mapper??
public?interface?CustomerMapper?{??
??
????CustomerMapper?INSTANCE?=?Mappers.getMapper(?CustomerMapper.class?);??
??
????@Mapping(source?=?"customerName",?target?=?"name")??
????Customer?toCustomer(CustomerDto?customerDto);??
??
????@InheritInverseConfiguration??
????CustomerDto?fromCustomer(Customer?customer);??
}??

@Mapping(source = “customerName”, target = “name”)不是用來(lái)指定屬性映射的，如果兩個(gè)對(duì)象的屬性名相同是可以省略@Mapping的。

MapStruct生成的實(shí)現(xiàn)類：

@Generated(??
????value?=?"org.mapstruct.ap.MappingProcessor",??
????date?=?"2019-02-14T15:41:21+0800",??
????comments?=?"version:?1.3.0.Final,?compiler:?javac,?environment:?Java?1.8.0_181?(Oracle?Corporation)"??
)??
public?class?CustomerMapperImpl?implements?CustomerMapper?{??
??
????@Override??
????public?Customer?toCustomer(CustomerDto?customerDto)?{??
????????if?(?customerDto?==?null?)?{??
????????????return?null;??
????????}??
??
????????Customer?customer?=?new?Customer();??
??
????????customer.setName(?customerDto.customerName?);??
????????customer.setId(?customerDto.id?);??
??
????????return?customer;??
????}??
??
????@Override??
????public?CustomerDto?toCustomerDto(Customer?customer)?{??
????????if?(?customer?==?null?)?{??
????????????return?null;??
????????}??
??
????????CustomerDto?customerDto?=?new?CustomerDto();??
??
????????customerDto.customerName?=?customer.getName();??
????????customerDto.id?=?customer.getId();??
??
????????return?customerDto;??
????}??
}??

@InheritInverseConfiguration在這里的作用就是實(shí)現(xiàn)customerDto.customerName = customer.getName();功能的。如果沒(méi)有這個(gè)注解，toCustomerDto這個(gè)方法則不會(huì)有customerName 和name兩個(gè)屬性的對(duì)應(yīng)關(guān)系的。

8.使用Spring依賴注入

@Data??
@NoArgsConstructor??
@AllArgsConstructor??
public?class?Customer?{??
????private?Long?id;??
????private?String?name;??
}??
??
@Data??
public?class?CustomerDto?{??
????private?Long?id;??
????private?String?customerName;??
}??
??
//?這里主要是這個(gè)componentModel?屬性，它的值就是當(dāng)前要使用的依賴注入的環(huán)境??
@Mapper(componentModel?=?"spring")??
public?interface?CustomerMapper?{??
??
????@Mapping(source?=?"name",?target?=?"customerName")??
????CustomerDto?toCustomerDto(Customer?customer);??
}??

@Mapper(componentModel = “spring”)，表示把當(dāng)前Mapper類納入spring容器?？梢栽谄渌愔兄苯幼⑷肓耍?/p>

@SpringBootApplication??
@RestController??
public?class?DemoMapstructApplication?{??
??
?//?注入Mapper??
????@Autowired??
????private?CustomerMapper?mapper;??
??
????public?static?void?main(String[]?args)?{??
????????SpringApplication.run(DemoMapstructApplication.class,?args);??
????}??
??
????@GetMapping("/test")??
????public?String?test()?{??
????????Customer?customer?=?new?Customer(1L,?"zhangsan");??
????????CustomerDto?customerDto?=?mapper.toCustomerDto(customer);??
????????return?customerDto.toString();??
????}??
??
}??

看一下由mapstruct自動(dòng)生成的類文件，會(huì)發(fā)現(xiàn)標(biāo)記了@Component注解。

@Generated(??
????value?=?"org.mapstruct.ap.MappingProcessor",??
????date?=?"2019-02-14T15:54:17+0800",??
????comments?=?"version:?1.3.0.Final,?compiler:?javac,?environment:?Java?1.8.0_181?(Oracle?Corporation)"??
)??
@Component??
public?class?CustomerMapperImpl?implements?CustomerMapper?{??
??
????@Override??
????public?CustomerDto?toCustomerDto(Customer?customer)?{??
????????if?(?customer?==?null?)?{??
????????????return?null;??
????????}??
??
????????CustomerDto?customerDto?=?new?CustomerDto();??
??
????????customerDto.setCustomerName(?customer.getName()?);??
????????customerDto.setId(?customer.getId()?);??
??
????????return?customerDto;??
????}??
}??

9.自定義類型轉(zhuǎn)換

有時(shí)候，在對(duì)象轉(zhuǎn)換的時(shí)候可能會(huì)出現(xiàn)這樣一個(gè)問(wèn)題，就是源對(duì)象中的類型是Boolean類型，而目標(biāo)對(duì)象類型是String類型，這種情況可以通過(guò)@Mapper的uses屬性來(lái)實(shí)現(xiàn)：

@Data??
@NoArgsConstructor??
@AllArgsConstructor??
public?class?Customer?{??
????private?Long?id;??
????private?String?name;??
????private?Boolean?isDisable;??
}??
??
@Data??
public?class?CustomerDto?{??
????private?Long?id;??
????private?String?customerName;??
????private?String?disable;??
}??

定義轉(zhuǎn)換規(guī)則的類：

public?class?BooleanStrFormat?{??
????public?String?toStr(Boolean?isDisable)?{??
????????if?(isDisable)?{??
????????????return?"Y";??
????????}?else?{??
????????????return?"N";??
????????}??
????}??
????public?Boolean?toBoolean(String?str)?{??
????????if?(str.equals("Y"))?{??
????????????return?true;??
????????}?else?{??
????????????return?false;??
????????}??
????}??
}??

定義Mapper，@Mapper( uses = { BooleanStrFormat.class})，注意，這里的users屬性用于引用之前定義的轉(zhuǎn)換規(guī)則的類：

@Mapper(?uses?=?{?BooleanStrFormat.class})??
public?interface?CustomerMapper?{??
??
????CustomerMapper?INSTANCES?=?Mappers.getMapper(CustomerMapper.class);??
??
????@Mappings({??
????????????@Mapping(source?=?"name",?target?=?"customerName"),??
????????????@Mapping(source?=?"isDisable",?target?=?"disable")??
????})??
????CustomerDto?toCustomerDto(Customer?customer);??
}??

這樣子，Customer類中的isDisable屬性的true就會(huì)轉(zhuǎn)變成CustomerDto中的disable屬性的yes。

MapStruct自動(dòng)生成的類中的代碼：

@Generated(??
????value?=?"org.mapstruct.ap.MappingProcessor",??
????date?=?"2019-02-14T16:49:18+0800",??
????comments?=?"version:?1.3.0.Final,?compiler:?javac,?environment:?Java?1.8.0_181?(Oracle?Corporation)"??
)??
public?class?CustomerMapperImpl?implements?CustomerMapper?{??
??
?//?引用?uses?中指定的類??
????private?final?BooleanStrFormat?booleanStrFormat?=?new?BooleanStrFormat();??
??
????@Override??
????public?CustomerDto?toCustomerDto(Customer?customer)?{??
????????if?(?customer?==?null?)?{??
????????????return?null;??
????????}??
??
????????CustomerDto?customerDto?=?new?CustomerDto();??
??//?轉(zhuǎn)換方式的使用??
????????customerDto.setDisable(?booleanStrFormat.toStr(?customer.getIsDisable()?)?);??
????????customerDto.setCustomerName(?customer.getName()?);??
????????customerDto.setId(?customer.getId()?);??
??
????????return?customerDto;??
????}??
}??

要注意的是，如果使用了例如像spring這樣的環(huán)境，Mapper引入uses類實(shí)例的方式將是自動(dòng)注入，那么這個(gè)類也應(yīng)該納入Spring容器：

CustomerMapper.java指定使用spring

@Mapper(componentModel?=?"spring",?uses?=?{?BooleanStrFormat.class})??
public?interface?CustomerMapper?{??
??
????CustomerMapper?INSTANCES?=?Mappers.getMapper(CustomerMapper.class);??
??
????@Mappings({??
????????????@Mapping(source?=?"name",?target?=?"customerName"),??
????????????@Mapping(source?=?"isDisable",?target?=?"disable")??
????})??
????CustomerDto?toCustomerDto(Customer?customer);??
}??

轉(zhuǎn)換類要加入Spring容器：

@Component??
public?class?BooleanStrFormat?{??
????public?String?toStr(Boolean?isDisable)?{??
????????if?(isDisable)?{??
????????????return?"Y";??
????????}?else?{??
????????????return?"N";??
????????}??
????}??
????public?Boolean?toBoolean(String?str)?{??
????????if?(str.equals("Y"))?{??
????????????return?true;??
????????}?else?{??
????????????return?false;??
????????}??
????}??
}??

MapStruct自動(dòng)生成的類：

@Generated(??
????value?=?"org.mapstruct.ap.MappingProcessor",??
????date?=?"2019-02-14T16:55:35+0800",??
????comments?=?"version:?1.3.0.Final,?compiler:?javac,?environment:?Java?1.8.0_181?(Oracle?Corporation)"??
)??
@Component??
public?class?CustomerMapperImpl?implements?CustomerMapper?{??
??
?//?使用自動(dòng)注入的方式引入??
????@Autowired??
????private?BooleanStrFormat?booleanStrFormat;??
??
????@Override??
????public?CustomerDto?toCustomerDto(Customer?customer)?{??
????????if?(?customer?==?null?)?{??
????????????return?null;??
????????}??
??
????????CustomerDto?customerDto?=?new?CustomerDto();??
??
????????customerDto.setDisable(?booleanStrFormat.toStr(?customer.getIsDisable()?)?);??
????????customerDto.setCustomerName(?customer.getName()?);??
????????customerDto.setId(?customer.getId()?);??
??
????????return?customerDto;??
????}??
}