Java 实体映射工具 MapStruct

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2020-09-11 16:21:38

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SpringBoot 项目开发
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MapStruct 文章源自JAVA秀-https://www.javaxiu.com/21038.html

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Java 实体映射工具 MapStruct_zhuyu19911016520-CSDN博客文章源自JAVA秀-https://www.javaxiu.com/21038.html

项目复杂性提升后，应用与应用之间，还有单独的应用细分模块之后，DO 一般不会让外部依赖，这时候需要在提供对外接口的模块里放 DTO 用于对象传输，也即是 DO 对象对内，DTO对象对外，DTO 可以根据业务需要变更，并不需要映射 DO 的全部属性。文章源自JAVA秀-https://www.javaxiu.com/21038.html

这种对象与对象之间的互相转换，就需要有一个专门用来解决转换问题的工具，毕竟每一个字段都 get/set 会很麻烦。文章源自JAVA秀-https://www.javaxiu.com/21038.html

MapStruct 就是这样的一个属性映射工具，只需要定义一个 Mapper 接口，MapStruct 就会自动实现这个映射接口，避免了复杂繁琐的映射实现。MapStruct官网地址： http://mapstruct.org/ API教程下载：mapstruct-guide.pdf Java 实体映射工具 MapStruct_zhuyu19911016520-CSDN博客文章源自JAVA秀-https://www.javaxiu.com/21038.html

工程中引入 maven 依赖文章源自JAVA秀-https://www.javaxiu.com/21038.html

<properties>
    <mapstruct.version>1.4.1.Final</mapstruct.version>
</properties>

<dependencies>
    <dependency>
         <groupId>org.mapstruct</groupId>
         <artifactId>mapstruct</artifactId>
         <version>${mapstruct.version}</version>
     </dependency>
     <dependency>
         <groupId>org.mapstruct</groupId>
         <artifactId>mapstruct-jdk8</artifactId>
         <version>${mapstruct.version}</version>
     </dependency>
     <dependency>
         <groupId>org.mapstruct</groupId>
         <artifactId>mapstruct-processor</artifactId>
         <version>${mapstruct.version}</version>
     </dependency>
</dependencies>

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>3.8.1</version>
            <configuration>
                <source>1.8</source> <!-- depending on your project -->
                <target>1.8</target> <!-- depending on your project -->
                <annotationProcessorPaths>
                    <path>
                        <groupId>org.mapstruct</groupId>
                        <artifactId>mapstruct-processor</artifactId>
                        <version>${mapstruct.version}</version>
                    </path>
                    <!-- other annotation processors -->
                </annotationProcessorPaths>
            </configuration>
        </plugin>
    </plugins>
</build>
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基本映射

有两个对象 User 和 UserDto需要转换，下面是这2个实体的属性文章源自JAVA秀-https://www.javaxiu.com/21038.html

public class User implements Serializable {

    private String id;
    private String name;
    private String phoneNumber;
    private String email;
    private String photoUrl;
    private Boolean deleted;
    private Boolean used;
    
    //getter and setter ...
}

public class UserDto implements Serializable {
    private String name;
    private String phoneNumber;
    private String email;
    
    //getter and setter ...
}
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添加UserModelConveter 接口，引入MapStruct相关功能文章源自JAVA秀-https://www.javaxiu.com/21038.html

import org.mapstruct.Mapper;
import org.mapstruct.factory.Mappers;

@Mapper(componentModel = "spring")
public interface UserModelConverter {

    UserModelConverter INSTANCE = Mappers.getMapper(UserModelConverter.class);
    /**
     * 使用示例
     * 如果实体模型中的字段不一致，通过@Mapping注解手动对应
     @Mapping(source = "name", target = "fullName")
     PersonDto personToPersonDto(Person person);

     List<UserVO1> toConvertVOList(List<User> source);//转换集合
     */

    UserDto userToUserDto(User user);
}
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若源对象属性与目标对象属性名字一致，会自动映射对应属性，不一样的需要手动指定文章源自JAVA秀-https://www.javaxiu.com/21038.html

还可以用 format 转成自己想要的类型，如：转换格式的 birthDateFormat 加了dateFormat文章源自JAVA秀-https://www.javaxiu.com/21038.html

如果某个属性你不想映射，可以加个 ignore=true文章源自JAVA秀-https://www.javaxiu.com/21038.html

@Mapper(componentModel = "spring")
public interface UserModelConverter {
    UserModelConverter INSTANCE = Mappers.getMapper(UserModelConverter.class);
    @Mappings({
        @Mapping(source = "birthday", target = "birth"),
        @Mapping(source = "birthday", target = "birthDateFormat", dateFormat = "yyyy-MM-dd HH:mm:ss"),
        @Mapping(target = "birthExpressionFormat", expression = "java(org.apache.commons.lang3.time.DateFormatUtils.format(person.getBirthday(),\"yyyy-MM-dd HH:mm:ss\"))"),
        @Mapping(source = "user.age", target = "age"),
        @Mapping(target = "email", ignore = true)
    })
    PersonDTO domain2dto(Person person);

    List<PersonDTO> domain2dto(List<Person> people);
}
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使用UserModelConverter转换model文章源自JAVA秀-https://www.javaxiu.com/21038.html

User user = userService.getUserByPhoneNumber(phoneNumber);
UserDto userDto = UserModelConverter.INSTANCE.userToUserDto(user);
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启动项目，编译之后， UserModelConverter 接口目录下会自动生成实现类，在 target/classes 下生成对应的实现类文章源自JAVA秀-https://www.javaxiu.com/21038.html

Java 实体映射工具 MapStruct_zhuyu19911016520-CSDN博客文章源自JAVA秀-https://www.javaxiu.com/21038.html

下面这个 UserModelConverterImpl 是自动生成的文章源自JAVA秀-https://www.javaxiu.com/21038.html

package com.zypcy.userservice.mapstruct;

import com.zypcy.userservice.dto.UserDto;
import com.zypcy.userservice.entity.User;
import org.springframework.stereotype.Component;

@Component
public class UserModelConverterImpl implements UserModelConverter {
    public UserModelConverterImpl() {
    }

    public UserDto userToUserDto(User user) {
        if (user == null) {
            return null;
        } else {
            UserDto userDto = new UserDto();
            userDto.setId(user.getId());
            userDto.setName(user.getName());
            userDto.setPhoneNumber(user.getPhoneNumber());
            userDto.setEmail(user.getEmail());
            userDto.setPhotoUrl(user.getPhotoUrl());
            userDto.setUpdateDate(user.getUpdateDate());
            return userDto;
        }
    }
}
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多对一

MapStruct 可以将几种类型的对象映射为另外一种类型，比如将多个 DO 对象转换为 DTO文章源自JAVA秀-https://www.javaxiu.com/21038.html

例子：两个DO 对象（Item 和 Sku），一个 DTO 对象 SkuDTO文章源自JAVA秀-https://www.javaxiu.com/21038.html

@NoArgsConstructor
@AllArgsConstructor
@Data
public class Item {
    private Long id;
    private String title;
}

@NoArgsConstructor
@AllArgsConstructor
@Data
public class Sku {
    private Long id;
    private String code;
    private Integer price;
}

@NoArgsConstructor
@AllArgsConstructor
@Data
public class SkuDTO {
    private Long skuId;
    private String skuCode;
    private Integer skuPrice;
    private Long itemId;
    private String itemName;
}
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创建 ItemConverter（映射）接口，MapStruct 就会自动实现该接口文章源自JAVA秀-https://www.javaxiu.com/21038.html

@Mapper
public interface ItemConverter {
    ItemConverter INSTANCE = Mappers.getMapper(ItemConverter.class);

    @Mappings({
            @Mapping(source = "sku.id",target = "skuId"),
            @Mapping(source = "sku.code",target = "skuCode"),
            @Mapping(source = "sku.price",target = "skuPrice"),
            @Mapping(source = "item.id",target = "itemId"),
            @Mapping(source = "item.title",target = "itemName")
    })
    SkuDTO domain2dto(Item item, Sku sku);
}
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创建测试类，讲 Item 和 Sku 两个 DO对象，映射成一个 DTO 对象 SkuDTO文章源自JAVA秀-https://www.javaxiu.com/21038.html

public class ItemConverterTest {
    @Test
    public void test() {
        Item item = new Item(1L, "iPhone X");
        Sku sku = new Sku(2L, "phone12345", 1000000);
        SkuDTO skuDTO = ItemConverter.INSTANCE.domain2dto(item, sku);
        assertNotNull(skuDTO);
        assertEquals(skuDTO.getSkuId(),sku.getId());
        assertEquals(skuDTO.getSkuCode(),sku.getCode());
        assertEquals(skuDTO.getSkuPrice(),sku.getPrice());
        assertEquals(skuDTO.getItemId(),item.getId());
        assertEquals(skuDTO.getItemName(),item.getTitle());
    }
}
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MapStruct 注解关键词

@Mapper 只有在接口加上这个注解， MapStruct 才会去实现该接口
    @Mapper 里有个 componentModel 属性，主要是指定实现类的类型，一般用到两个
    default：默认，可以通过 Mappers.getMapper(Class) 方式获取实例对象
    spring：在接口的实现类上自动添加注解 @Component，可通过 @Autowired 方式注入
@Mapping：属性映射，若源对象属性与目标对象名字一致，会自动映射对应属性
    source：源属性
    target：目标属性
    dateFormat：String 到 Date 日期之间相互转换，通过 SimpleDateFormat，该值为 SimpleDateFormat              的日期格式
    ignore: 忽略这个字段
@Mappings：配置多个@Mapping
@MappingTarget 用于更新已有对象
@InheritConfiguration 用于继承配置
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