springboot+mapstruct初尝试

在日常开发中，是不是经常遇到实体转换的需求，敲实体转换的代码让人头疼又无奈，特别是字段多的时候，常用的工具有BeanUtils，下面尝试一个开源项目mapstruct，可以轻松优雅的对PO、VO、DTO进行转换。
mapstruct是一种实体类映射框架，能够通过Java注解将一个实体类的属性安全地赋值给另一个实体类。有了mapstruct，只需要定义一个映射器接口，声明需要映射的方法，在编译过程中，mapstruct会自动生成该接口的实现类，实现将源对象映射到目标对象的效果。
实例

	<properties>
        <java.version>1.8</java.version>
        <org.mapstruct.version>1.4.1.Final</org.mapstruct.version>
        <org.projectlombok.version>1.18.12</org.projectlombok.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.mapstruct</groupId>
            <artifactId>mapstruct</artifactId>
            <version>${org.mapstruct.version}</version>
        </dependency>
        <dependency>
            <groupId>org.mapstruct</groupId>
            <artifactId>mapstruct-processor</artifactId>
            <version>${org.mapstruct.version}</version>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>${org.projectlombok.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
            <!-- maven-compiler-plugin 插件，解决 Lombok + MapStruct 组合 -->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.8.1</version>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                    <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>
                </configuration>
            </plugin>
        </plugins>
    </build>

关于lombok和mapstruct的版本兼容问题多说几句，maven插件要使用3.6.0版本以上、lombok使用1.16.16版本以上，另外编译的lombok mapstruct的插件不要忘了加上。
实体

@Data
@Builder
@AllArgsConstructor
@NoArgsConstructor
public class Student {

    private String name;
    private int age;
    private GenderEnum gender;
    private Double height;
    private Date birthday;

}
@Data
@Builder
@AllArgsConstructor
@NoArgsConstructor
public class Course {

    private String courseName;
    private int sortNo;
    private long id;

}
@Data
@Builder
@AllArgsConstructor
@NoArgsConstructor
public class StudentVO {

    private String name;
    private int age;
    private String gender;
    private Double height;
    private String birthday;

    private String course;
}

枚举

public enum GenderEnum {
    Male("1", "男"),
    Female("0", "女");

    private String code;
    private String name;

    public String getCode() {
        return this.code;
    }

    public String getName() {
        return this.name;
    }

    GenderEnum(String code, String name) {
        this.code = code;
        this.name = name;
    }
}

实体转换

@Mapper
public interface StudentConverter {

    StudentConverter INSTANCE = Mappers.getMapper(StudentConverter.class);

    @Mapping(source = "student.gender.name", target = "gender")
    @Mapping(source = "student.birthday", target = "birthday", dateFormat = "yyyy-MM-dd HH:mm:ss")
    StudentVO student2StudentVO(Student student);

    @Mapping(source = "student.gender.name", target = "gender")
    @Mapping(source = "student.birthday", target = "birthday", dateFormat = "yyyy-MM-dd HH:mm:ss")
    @Mapping(source = "course.courseName", target = "course")
    StudentVO studentAndCourse2StudentVO(Student student, Course course);

    List<StudentVO> students2StudentVOs(List<Student> studentList);

}

实体类的代码编写是少不了的，就算是用工具生成也肯定是要有的，需要编写的部分就算这个converter接口，编译完成后会自动生成相应的实现类。
测试

	@Test
    void contextLoads() {
        Student student = Student.builder().name("小明").age(6).gender(GenderEnum.Male).height(121.1).birthday(new Date()).build();
        System.out.println(student);
        //这行代码便是实际要用的代码
        StudentVO studentVO = StudentConverter.INSTANCE.student2StudentVO(student);
        System.out.println(studentVO);
    }

    @Test
    void test1() {
        Student student = Student.builder().name("小明").age(6).gender(GenderEnum.Male).height(121.1).birthday(new Date()).build();
        System.out.println(student);
        List<Student> list = new ArrayList<>();
        list.add(student);
        List<StudentVO> result = StudentConverter.INSTANCE.students2StudentVOs(list);
        System.out.println(result);
    }

    @Test
    void test2() {
        Student student = Student.builder().name("小明").age(6).gender(GenderEnum.Male).height(121.1).birthday(new Date()).build();
        Course course = Course.builder().id(1L).courseName("语文").build();
        StudentVO studentVO = StudentConverter.INSTANCE.studentAndCourse2StudentVO(student, course);
        System.out.println(studentVO);
    }

converter可以进行字段映射，改变字段类型，指定格式化的方式，包括一些日期的处理，List类型转换，多个对象转换到一个对象。
测试结果如下



还需深入理解其实现原理，加油吧，少年。