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代码简洁之道-mapstruct(图文)

第十三双眼睛2022-03-05【Java】人已围观

简介mapstruct的简单介绍及使用

要使用mapstruct，请确保你的jdk版本是1.8+。
官网：https://mapstruct.org/

1：导入依赖

<dependency>
   <groupId>org.mapstruct</groupId>
   <artifactId>mapstruct-processor</artifactId>
   <version>1.2.0.Final</version>
</dependency>
<dependency>
   <groupId>org.mapstruct</groupId>
   <artifactId>mapstruct</artifactId>
   <version>${mapstruct.version}</version>
</dependency>

2：准备几个实体类

public class UserAddRequest {

   private String name;

   private Integer age;

   private Long birthday;

   private Double salary;

   private List<HouseAddRequest> houseList;

}

public class HouseAddRequest {

private String estateName;

private String address;

private Integer building;

private Integer unit;

private Integer floor;

private String houseNumber;

}

public class UserAddParam {

   private String name;

   private Integer age;

   private Date birthday;

   private Double salary;

   private List<HouseAddParam> houseList;

}

public class HouseAddParam {

private String estateName;

private String address;

private Integer building;

private Integer unit;

private Integer floor;

private String houseCode;

}

定义一个映射器

@Mapper(componentModel = "spring")
public abstract class HouseConverter {

@Mappings({
@Mapping(target = "houseCode",source = "houseNumber")
})
public abstract HouseAddParam request2param(HouseAddRequest request);

}

@Mapper(componentModel ="spring",imports = {Date.class})
public abstract class UserConverter {

   @Autowired
   private HouseConverter houseConverter;

   @Mappings({
       @Mapping(target = "birthday",expression = "java(new Date(request.getBirthday()))")
   })
   public abstract UserAddParam request2param(UserAddRequest request);

   public HouseAddParam houseRequest2param(HouseAddRequest request){
       return houseConverter.request2param(request);
   }

}

定义一个定时任务，我们来测试一下

@Scheduled(cron = "0/10 * * * * *")
public void converterUserAddRequest2AddParam(){
   UserAddRequest userAddRequest = new UserAddRequest();
   userAddRequest.setName("张三");
   userAddRequest.setAge(1);
   userAddRequest.setBirthday(new Date().getTime());
   userAddRequest.setSalary(5434.56);
   List<HouseAddRequest> houseAddRequestList = new ArrayList<>();
   HouseAddRequest houseAddRequest1 = new HouseAddRequest();
   houseAddRequest1.setAddress("杭州滨江区");
   houseAddRequest1.setEstateName("缤纷东苑");
   houseAddRequest1.setBuilding(3);
   houseAddRequest1.setUnit(1);
   houseAddRequest1.setFloor(4);
   houseAddRequest1.setHouseNumber("401");
   houseAddRequestList.add(houseAddRequest1);
   userAddRequest.setHouseList(houseAddRequestList);
   UserAddParam userAddParam = userConverter.request2param(userAddRequest);
   System.out.println("=================================================");
   System.out.println(userAddParam);
}

结果成功输出了
UserAddParam(name=张三, age=1, birthday=Sat Mar 05 12:27:10 CST 2022, salary=5434.56,
houseList=[HouseAddParam(estateName=缤纷东苑, address=杭州滨江区, building=3, unit=1, floor=4, houseCode=401)])

提示：8种基本类型和String可以自动转换

数字格式化：
我们现在把目标对象的薪资属性salary改为字符串，并且要保留一位小数，做如下配置就可以做到

@Mapping(target = "salary",source = "salary",numberFormat = "#0.0")

日期格式化
我们现在把目标对象的生日属性birthday改为字符串，格式要求2012-12-12 12:12:12这种做如下配置就可以做到
我们首先需要将源对象的生日属性birthday类型改为Date

@Mapping(target = "birthday",dateFormat = "yyyy-MM-dd HH:mm:ss")

忽略目标对象的某个属性赋值

@Mapping(target = "age",ignore = true)

自定义处理方法

@AfterMapping
public void afterMapping(@MappingTarget UserAddParam userAddParam,UserAddRequest request){

}

@AfterMapping 注解的作用是，当UserAddRequest 到 UserAddParam 转换方法完成后，会来调用这个方法
@MappingTarget 注解用来标记目标对象

当属性很多，并且名字都相同，但是只想映射少量属性时该怎么办呢，如果一个一个设置忽略，则会很多。用如下注解就可以解决
@BeanMapping(ignoreByDefault = true)
此注解的作用是，先禁用默认映射。再手动设置我们想映射的属性就可以了。

@InheritConfiguration
MapStruct允许对映射关系进行继承，使用@InheritConfiguration标记当前方法继承其他映射方法的映射关系。会自动查找相同类型映射源、映射目标的方法进行继承，如果存在多个相同类型的方法，则需要手工指定

@InheritInverseConfiguration
除了正向继承规则外，还可以进行规则逆向继承，从被继承方法的目标对象映射到源对象
只会继承@Mapping 不会继承@BeanMapping

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