Springboot集成mapstruct

一、什麼是mapstruct

MapStruct是一個代碼生成器的工具類，簡化了不同的Java Bean之間映射的處理，所以映射指的就是從一個實體變化成一個實體。在實際項目中，我們經常會將PO轉DTO、DTO轉PO等一些實體間的轉換。在轉換時大部分屬性都是相同的，只有少部分的不同，這時我們可以通過mapStruct的一些註解來匹配不同屬性，可以讓不同實體之間的轉換變的簡單。
MapStruct官網地址： http://mapstruct.org/

二、添加依賴

<!--MapStruct依賴-->
<!-- https://mvnrepository.com/artifact/org.mapstruct/mapstruct-jdk8 -->
<dependency>
    <groupId>org.mapstruct</groupId>
    <artifactId>mapstruct-jdk8</artifactId>
    <version>1.0.0.Final</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.mapstruct/mapstruct-processor -->
<dependency>
    <groupId>org.mapstruct</groupId>
    <artifactId>mapstruct-processor</artifactId>
    <version>1.0.0.Final</version>
</dependency>

三、mapstruct實體間的轉換

//Info.java
public class Info{
    private Integer userId;
    private String email;
    private Integer score;
    private String remark;
    //constructor, getters, setters etc.
}

//InfoDto.java
public class InfoDto{
    private Integer id;
    private Integer value;
    private String remark;
    private User user;
    //constructor, getters, setters etc.
}

//User.java
public class User{
    private Integer userId;
    private String email;
    //constructor, getters, setters etc.
}

四、mapper接口

要生成一個PeopleDTO與PeopleEntity對象相互轉換的映射器，我們需要定義一個mapper接口。像這兩個實體類有些屬性不一樣時，我們可以通過@Mapping註解來進行轉換.

• @Mapper註解標記這個接口作爲一個映射接口，並且是編譯時MapStruct處理器的入口。
• @Mapping解決源對象和目標對象中，屬性名字不同的情況。
• Mappers.getMapper自動生成的接口的實現可以通過Mapper的class對象獲取,從而讓客戶端可以訪問Mapper接口的實現。

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

    /**
     * PO轉DTO
     *
     * @param info PO
     * @return DTO
     */
    @Mapping(target = "value", source = "score")
    @Mapping(target = "user.userId", source = "userId")
    @Mapping(target = "user.email", source = "email")
    InfoDTO entityToDTO(Info info);

    /**
     * DTO轉PO
     *
     * @param infoDTO DTO
     * @param entity    PO
     */
    @Mapping(target = "score", source = "value")
    @Mapping(target = "userId", source = "user.userId")
    @Mapping(target = "email", source = "user.email")
    void updateInfoFromDto(InfoDTO InfoDTO, @MappingTarget Info info);
}

當運行是將會自動編譯我們的InfoMapper.java

下面是我在學習時寫的Mapper文件以及編譯後的一個文件

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

    TeamVo poToTeamVo(TeamPo teamPo);

    Team poToTeamDo(TeamPo teamPo);

    List<TeamVo> poListToVoList(List<TeamPo> teamPoList);
}

@Generated(
    value = "org.mapstruct.ap.MappingProcessor",
    date = "2019-08-08T13:30:54+0800",
    comments = "version: 1.0.0.Final, compiler: javac, environment: Java 1.8.0_211 (Oracle Corporation)"
)
@Component
public class TeamMapperImpl implements TeamMapper {

    @Override
    public TeamVo poToTeamVo(TeamPo teamPo) {
        if ( teamPo == null ) {
            return null;
        }

        TeamVo teamVo = new TeamVo();

        teamVo.setId( teamPo.getId() );
        teamVo.setName( teamPo.getName() );
        teamVo.setDepartmentId( teamPo.getDepartmentId() );
        teamVo.setDepartmentName( teamPo.getDepartmentName() );

        return teamVo;
    }

    @Override
    public Team poToTeamDo(TeamPo teamPo) {
        if ( teamPo == null ) {
            return null;
        }

        Team team = new Team();

        team.setId( teamPo.getId() );
        team.setName( teamPo.getName() );
        team.setDepartmentId( teamPo.getDepartmentId() );

        return team;
    }

    @Override
    public List<TeamVo> poListToVoList(List<TeamPo> teamPoList) {
        if ( teamPoList == null ) {
            return null;
        }

        List<TeamVo> list = new ArrayList<TeamVo>();
        for ( TeamPo teamPo : teamPoList ) {
            list.add( poToTeamVo( teamPo ) );
        }

        return list;
    }
}

五、注意

1、 由於編譯可能不及時的原因，所以一開始遇到了修改了po或者dto的一個類，但是mapper沒有及時的重新編譯，所以dto，po，vo有更改的話，建議先clean一下之後重新編譯然後運行

2、 在使用mapstruct + lombok時要注意maven-comiler-plugin插件版本一定要在3.6.0以上，若版本低，則會報找不到屬性的錯誤
下面是一個依賴模板

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.1.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>xyz.suiwo</groupId>
    <artifactId>gradingdog</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>gradingdog</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
        <org.mapstruct.version>1.2.0.Beta2</org.mapstruct.version>
        <org.projectlombok.version>1.16.14</org.projectlombok.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>2.0.1</version>
        </dependency>

        <!--MapStruct依賴-->
        <dependency>
            <groupId>org.mapstruct</groupId>
            <artifactId>mapstruct</artifactId> <!-- use mapstruct-jdk8 for Java 8 or higher -->
            <version>${org.mapstruct.version}</version>
        </dependency>

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

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.6.0</version>
                <configuration>
                    <source>${java.version}</source> <!-- or higher, depending on your project -->
                    <target>${java.version}</target> <!-- or higher, depending on your project -->
                    <annotationProcessorPaths>
                        <path>
                            <groupId>org.projectlombok</groupId>
                            <artifactId>lombok</artifactId>
                            <version>${org.projectlombok.version}</version>
                        </path>
                        <path>
                            <groupId>org.mapstruct</groupId>
                            <artifactId>mapstruct-processor</artifactId>
                            <version>${org.mapstruct.version}</version>
                        </path>
                    </annotationProcessorPaths>
                    <compilerArgs>
                        <arg>-Amapstruct.suppressGeneratorTimestamp=true</arg>
                        <arg>-Amapstruct.defaultComponentModel=spring</arg>
                    </compilerArgs>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>