使用 MapStruct 的嵌套列表映射

Question

对于以下场景，我如何使用 MapStruct 进行 bean 映射。

class Source {
private String sourceId;
private List<Course> courses;  //always returns only one course
}

class Course {
private String courseName;
private List<Student> students; 
}

class Student {
private String studentName;
}

class Target {
private String targetId;
private String subjectName;
private List<Member> members;
}

class Member {
private String memberName;
}

现在我想将 sourceId 映射到 targetId，将 courseName 映射到 subjectName，将 studentName 映射到 memberName（列表到列表）。

Answer 1

首先Source 总是包含一个课程，为什么不将其设为Course 元素而不是List？

如果你这样做，映射会简单得多。根据您当前的设置，它有点复杂。

@Mapper
public interface MyMapper {

    @Mapping(target = "targetId", source = "sourceId")
    @Mapping(target = "subjectName", source = "courses")
    @Mapping(target = "members", source = "courses")
    Target map(Source source);

    default String subjectName(List<Course> courses) {
        if (courses == null || courses.isEmpty()) {
            return null;
        }
        return courses.get(0).getCourseName();
    }

    default List<Member> toMembersFromCourses(List<Course> courses) {
        if (courses == null || courses.isEmpty()) {
            return null;
        }
        return toMembers(courses.get(0).getStudents());
    }

    List<Member> toMembers(List<Student> students);

    @Mapping(target = "memberName", source = "studentName")
    Member toMember(Student student);
}

如果Course 不是列表。那么你可以用 1.2.0.Final 做得更优雅。

@Mapper
public interface MyMapper {

    @Mapping(target = "targetId", source = "sourceId")
    @Mapping(target = "subjectName", source = "course.courseName")
    @Mapping(target = "members", source = "course.students")
    Target map(Source source);

    @Mapping(target = "memberName", source = "studentName")
    Member toMember(Student student);
}