はじめに

Beanの変換に詰め替え作業は手動で実施するとコード量は増えてしまい、メンテナンス性は良くないです。
BeanUtils.copyPropertiesのような便利メソッドがありますが、ほかのマッピングライブラリをまとめてみます。

FasterXML ObjectMapper

JSON関連する処理はこれを使うと便利です。

使い方

build.gradleに追加

build.gradle

// https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-databind
compile group: 'com.fasterxml.jackson.core', name: 'jackson-databind', version: '2.9.8'

Beanクラス作成

package com.test.lombok;

import lombok.Getter;
import lombok.Setter;
import lombok.ToString;

@Getter
@Setter
@ToString
public class User {
    private String userId;

    private String userName;

    private String age;

    private String gender;
}

user.jsonサンプル作成

user.json

{
"userId": "user001",
"userName": "テスト 太郎",
"age": 20,
"gender": "famale"
}

テストコード

package com.test.lombok;

import java.io.File;
import java.util.Map;

import com.fasterxml.jackson.databind.ObjectMapper;

public class TestMain {

    public static void main(String[] args) throws Exception {
        ObjectMapper mapper = new ObjectMapper();

        // ファイルパスで指定
        User user1 = mapper.readValue(
                new File("C:\\workspace_sts\\lombok\\src\\main\\java\\com\\test\\lombok\\user.json"), User.class);
        System.out.println(user1);

        // URL形式で指定
        User user2 = mapper.readValue(TestMain.class.getResource("user.json"), User.class);
        System.out.println(user2);

        // 文字列から変換
        User user3 = mapper.readValue(
                "{\"userId\":\"user001\", \"userName\": \"テスト 太郎２\", \"age\": 22, \"gender\": \"male\"}", User.class);
        System.out.println(user3);

        // オブジェクトから文字列に変換
        String jsonString = mapper.writeValueAsString(user3);
        System.out.println(jsonString);

        // 文字列からMapに変換
        Map<String, String> userMap = mapper.readValue(jsonString, Map.class);
        System.out.println(userMap);

    }

}

結果：

User(userId=user001, userName=テスト太郎, age=20, gender=famale)
User(userId=user001, userName=テスト太郎, age=20, gender=famale)
User(userId=user001, userName=テスト太郎２, age=22, gender=male)
{"userId":"user001","userName":"テスト太郎２","age":"22","gender":"male"}
{userId=user001, userName=テスト太郎２, age=22, gender=male}

ModelMapper

使い方

build.gradleに追加

build.gradle

    // https://mvnrepository.com/artifact/org.modelmapper/modelmapper
    compile group: 'org.modelmapper', name: 'modelmapper', version: '2.3.5'

元Beanクラス

package com.test.lombok;

import lombok.Data;

@Data
public class User {
    private String userId;

    private String userName;

    private String age;

    private String gender;

    private Address addr;
}

@Data
class Address {
    private String zipCode;
    private String address1;
    private String address2;
    private String address3;
}

DTOクラス

package com.test.lombok;

import lombok.Getter;
import lombok.Setter;
import lombok.ToString;

@Getter
@Setter
@ToString
public class UserDTO {
    private String userId;

    private String userName;

    private String age;

    private String gender;

    private String addrZipCode;

    private String addrAddress1;

    private String addrAddress2;

    private String addrAddress3;
}

テストコード

package com.test.lombok;

import org.modelmapper.ModelMapper;

public class TestMain {

    public static void main(String[] args) throws Exception {
        ModelMapper modelMapper = new ModelMapper();

        User user = new User();
        user.setUserId("user001");
        user.setUserName("テスト");
        user.setAge("18");
        user.setGender("male");
        Address addr = new Address();
        addr.setZipCode("984-0031");
        addr.setAddress1("○○県");
        user.setAddr(addr );

        UserDTO userDTO = modelMapper.map(user, UserDTO.class);
        System.out.println(userDTO);

    }

}

結果：

UserDTO(userId=user001, userName=テスト, age=18, gender=male, addrZipCode=984-0031, addrAddress1=○○県, addrAddress2=null, addrAddress3=null)

明示的にマッピング（Explicit Mapping）

package com.test.lombok;

import org.modelmapper.ModelMapper;
import org.modelmapper.TypeMap;

public class TestMain {

    public static void main(String[] args) throws Exception {
        ModelMapper modelMapper = new ModelMapper();

        User user = new User();
        user.setUserId("user001");
        user.setUserName("テスト");
        user.setAge("18");
        user.setGender("male");
        Address addr = new Address();
        addr.setZipCode("984-0031");
        addr.setAddress1("○○県");
        user.setAddr(addr);

        TypeMap<User, UserDTO> typeMap = modelMapper.typeMap(User.class, UserDTO.class).addMappings(mapper -> {
            mapper.map(src -> src.getAddr().getZipCode(), UserDTO::setAddrZipCode);
            mapper.map(src -> src.getAddr().getAddress1(), UserDTO::setAddrAddress1);
        });

        System.out.println(typeMap.map(user));

    }

}

結果：

UserDTO(userId=user001, userName=テスト, age=18, gender=male, addrZipCode=984-0031, addrAddress1=○○県, addrAddress2=null, addrAddress3=null)

SpringBootのControllerにてFormのBeanから自分のDTOに変換するに使うと便利です。

MapStruct

使い方

build.gradleに追加

build.gradle

plugins {
    id 'java'
    id 'net.ltgt.apt' version '0.20'
}

repositories {
    jcenter()
}

dependencies {
    // lombok
    compileOnly "org.projectlombok:lombok:1.18.12"
    annotationProcessor "org.projectlombok:lombok:1.18.12"

    // https://mvnrepository.com/artifact/org.mapstruct/mapstruct
    implementation  group: 'org.mapstruct', name: 'mapstruct', version: '1.3.1.Final'

    // https://mvnrepository.com/artifact/org.mapstruct/mapstruct-processor
    annotationProcessor group: 'org.mapstruct', name: 'mapstruct-processor', version: '1.3.1.Final'

}

[compileJava, compileTestJava]*.options*.encoding= "UTF-8"

sourceSets {
    main.java.srcDirs += "build/generated/sources/annotationProcessor/java/main"
}

Mapperインタフェース

package com.test.lombok;

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

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

    @Mapping(source = "addr.zipCode", target = "addrZipCode")
    @Mapping(source = "addr.address1", target = "addrAddress1")
    @Mapping(source = "addr.address2", target = "addrAddress2")
    UserDTO userToUserDTO(User user);
}

上記定義し、ビルドするとbuild\generated\sources\annotationProcessor\java\main\com\test\lombokにUserMapperImpl.javaクラスが生成されます。

UserMapperImpl.java

package com.test.lombok;

import javax.annotation.Generated;

@Generated(
    value = "org.mapstruct.ap.MappingProcessor",
    date = "2020-06-28T21:47:47+0900",
    comments = "version: 1.3.1.Final, compiler: javac, environment: Java 1.8.0_201 (Oracle Corporation)"
)
public class UserMapperImpl implements UserMapper {

    @Override
    public UserDTO userToUserDTO(User user) {
        if ( user == null ) {
            return null;
        }

        UserDTO userDTO = new UserDTO();

        userDTO.setAddrAddress2( userAddrAddress2( user ) );
        userDTO.setAddrAddress1( userAddrAddress1( user ) );
        userDTO.setAddrZipCode( userAddrZipCode( user ) );
        userDTO.setUserId( user.getUserId() );
        userDTO.setUserName( user.getUserName() );
        userDTO.setAge( user.getAge() );
        userDTO.setGender( user.getGender() );

        return userDTO;
    }

    private String userAddrAddress2(User user) {
        if ( user == null ) {
            return null;
        }
        Address addr = user.getAddr();
        if ( addr == null ) {
            return null;
        }
        String address2 = addr.getAddress2();
        if ( address2 == null ) {
            return null;
        }
        return address2;
    }

    private String userAddrAddress1(User user) {
        if ( user == null ) {
            return null;
        }
        Address addr = user.getAddr();
        if ( addr == null ) {
            return null;
        }
        String address1 = addr.getAddress1();
        if ( address1 == null ) {
            return null;
        }
        return address1;
    }

    private String userAddrZipCode(User user) {
        if ( user == null ) {
            return null;
        }
        Address addr = user.getAddr();
        if ( addr == null ) {
            return null;
        }
        String zipCode = addr.getZipCode();
        if ( zipCode == null ) {
            return null;
        }
        return zipCode;
    }
}

テストコード

package com.test.lombok;

public class TestMain {

    public static void main(String[] args) throws Exception {

        User user = new User();
        user.setUserId("user001");
        user.setUserName("テスト");
        user.setAge("18");
        user.setGender("male");
        Address addr = new Address();
        addr.setZipCode("984-0031");
        addr.setAddress1("○○県");
        user.setAddr(addr);


        UserDTO userDTO = UserMapper.INSTANCE.userToUserDTO(user);

        System.out.println(userDTO);

    }
}

結果：

UserDTO(userId=user001, userName=テスト, age=18, gender=male, addrZipCode=984-0031, addrAddress1=○○県, addrAddress2=null, addrAddress3=null)

ClassNotFoundエラー

Exception in thread "main" java.lang.ExceptionInInitializerError
    at com.test.lombok.TestMain.main(TestMain.java:18)
Caused by: java.lang.RuntimeException: java.lang.ClassNotFoundException: Cannot find implementation for com.test.lombok.UserMapper
    at org.mapstruct.factory.Mappers.getMapper(Mappers.java:61)
    at com.test.lombok.UserMapper.<clinit>(UserMapper.java:9)
    ... 1 more
Caused by: java.lang.ClassNotFoundException: Cannot find implementation for com.test.lombok.UserMapper
    at org.mapstruct.factory.Mappers.getMapper(Mappers.java:75)
    at org.mapstruct.factory.Mappers.getMapper(Mappers.java:58)

build.gradleにsourceSetsを追加

build.gradle

sourceSets {
    main.java.srcDirs += "build/generated/sources/annotationProcessor/java/main"
}

詳細Doc：https://mapstruct.org/documentation/stable/reference/html/

Dozer

使い方

build.gradleに追加

build.gradle

// https://mvnrepository.com/artifact/com.github.dozermapper/dozer-core
compile group: 'com.github.dozermapper', name: 'dozer-core', version: '6.5.0'

テストコード

package com.test.lombok;

import org.modelmapper.ModelMapper;
import org.modelmapper.TypeMap;

import com.github.dozermapper.core.DozerBeanMapperBuilder;
import com.github.dozermapper.core.Mapper;

public class TestMain {

    public static void main(String[] args) throws Exception {

        User user = new User();
        user.setUserId("user001");
        user.setUserName("テスト");
        user.setAge("18");
        user.setGender("male");
        Address addr = new Address();
        addr.setZipCode("984-0031");
        addr.setAddress1("○○県");
        user.setAddr(addr);

        Mapper mapper = DozerBeanMapperBuilder.buildDefault();
        UserDTO userDTO = mapper.map(user, UserDTO.class);

        System.out.println(userDTO);

    }
}

結果：

UserDTO(userId=user001, userName=テスト, age=18, gender=male, addrZipCode=null, addrAddress1=null, addrAddress2=null, addrAddress3=null)

同じ項目名はコピーされましたが、それ以外nullでした。

違う項目の場合はXML、API、アノテーションで定義して対応可能

違う項目名の場合は @Mapping("binaryData")のように設定で対応可能ですが、複雑のタイプの場合はXMLで設定する必要があります。

好きなライブラリを選択すればと思います。

以上

JAVAオブジェクトマッピングライブラリ

はじめに

FasterXML ObjectMapper

使い方

build.gradleに追加

Beanクラス作成

user.jsonサンプル作成

テストコード

ModelMapper

使い方

build.gradleに追加

元Beanクラス

DTOクラス

テストコード

明示的にマッピング（Explicit Mapping）

MapStruct

使い方

build.gradleに追加

Mapperインタフェース

テストコード

ClassNotFoundエラー

Dozer

使い方

build.gradleに追加

テストコード

違う項目の場合はXML、API、アノテーションで定義して対応可能