Java8处理扁平化的List为层级结构

数据示例

原始扁平的列表如下：

json data: [
    {
        "chapterTitle":"怎么说员工才爱听",
        "chapterUuid":"a459cb9d-4abf-4607-aa24-92e614a884c3",
        "chapterWeight":1,
        "courseId":2174,
        "id":0,
        "lessonCourseId":100,
        "lessonTitle":"说话的艺术,第1讲",
        "lessonUuid":"82b2e1eb-849d-4450-9a62-49eb69eb2f11",
        "lessonWeight":1,
        "tenantId":22
    },
    {
        "chapterTitle":"怎么说员工才爱听",
        "chapterUuid":"a459cb9d-4abf-4607-aa24-92e614a884c3",
        "chapterWeight":1,
        "courseId":2174,
        "id":1,
        "lessonCourseId":101,
        "lessonTitle":"说话的艺术,第2讲",
        "lessonUuid":"b9741ea7-6b48-4354-b344-a44c6f147dad",
        "lessonWeight":2,
        "tenantId":22
    },
    {
        "chapterTitle":"怎么说员工才爱听",
        "chapterUuid":"a459cb9d-4abf-4607-aa24-92e614a884c3",
        "chapterWeight":1,
        "courseId":2174,
        "id":2,
        "lessonCourseId":102,
        "lessonTitle":"说话的艺术,第3讲",
        "lessonUuid":"8848245f-d3b1-4023-a8ec-6015c4008837",
        "lessonWeight":3,
        "tenantId":22
    },
    {
        "chapterTitle":"怎么说员工才爱听",
        "chapterUuid":"a459cb9d-4abf-4607-aa24-92e614a884c3",
        "chapterWeight":1,
        "courseId":2174,
        "id":3,
        "lessonCourseId":103,
        "lessonTitle":"说话的艺术,第4讲",
        "lessonUuid":"e251fda2-62c6-45e2-96ae-80cdf84bccab",
        "lessonWeight":4,
        "tenantId":22
    },
    {
        "chapterTitle":"怎么说员工才爱听",
        "chapterUuid":"a459cb9d-4abf-4607-aa24-92e614a884c3",
        "chapterWeight":1,
        "courseId":2174,
        "id":4,
        "lessonCourseId":104,
        "lessonTitle":"说话的艺术,第5讲",
        "lessonUuid":"56b55099-d047-4a65-99b4-deaef7146d62",
        "lessonWeight":5,
        "tenantId":22
    }
]

处理为带层次结构后：

[
    {
        "children":[
            {
                "id":0,
                "lessonCourseId":100,
                "tenantId":22,
                "title":"3分钟玩转HSR如何提升房源质量分,第1讲",
                "uuid":"c008e373-734b-4647-be17-a9843be731db",
                "weight":1
            },
            {
                "id":1,
                "lessonCourseId":101,
                "tenantId":22,
                "title":"3分钟玩转HSR如何提升房源质量分,第2讲",
                "uuid":"64540c91-413f-4bfa-a5b0-41c70a451ee7",
                "weight":2
            },
            {
                "id":2,
                "lessonCourseId":102,
                "tenantId":22,
                "title":"3分钟玩转HSR如何提升房源质量分,第3讲",
                "uuid":"d57ba179-a6f2-4c17-8798-c2a54d63d367",
                "weight":3
            },
            {
                "id":3,
                "lessonCourseId":103,
                "tenantId":22,
                "title":"3分钟玩转HSR如何提升房源质量分,第4讲",
                "uuid":"16394439-5a17-44c4-b085-6cf2e119d49d",
                "weight":4
            },
            {
                "id":4,
                "lessonCourseId":104,
                "tenantId":22,
                "title":"3分钟玩转HSR如何提升房源质量分,第5讲",
                "uuid":"57cf2d26-3481-46b8-b3e6-a089eee9fad8",
                "weight":5
            }
        ],
        "title":"怎么说员工才爱听",
        "uuid":"a459cb9d-4abf-4607-aa24-92e614a884c3",
        "weight":1
    }
]

代码示例

处理思路：先分组得到Map> 再处理每个K,V

List<DxSeriesCourseChapter> courseChapters = Lists.newArrayList();
        for (int i = 0; i < 5; i++) {
            DxSeriesCourseChapter data = new DxSeriesCourseChapter();
            data.setId(Long.valueOf(i + 0));
            data.setTenantId(22L);
            data.setCourseId(2174L);
            data.setChapterTitle("怎么说员工才爱听");
            data.setChapterUuid("a459cb9d-4abf-4607-aa24-92e614a884c3");
            data.setChapterWeight(1);
            data.setLessonTitle(String.format("说话的艺术,第%s讲", (i + 1)));
            data.setLessonWeight((i + 1));
            data.setLessonUuid(UUID.randomUUID().toString());
            data.setLessonCourseId(Long.valueOf(i + 100));
            courseChapters.add(data);
        }
        logger.info("json data: {}", JSON.toJSONString(courseChapters, true));
        List<DxSeriesCourseChapterVo> chapters = courseChapters.stream()
                .collect(Collectors.groupingBy(courseChapter -> {
                    DxSeriesCourseChapterVo chapterVo = new DxSeriesCourseChapterVo();
                    chapterVo.setTitle(courseChapter.getChapterTitle());
                    chapterVo.setWeight(courseChapter.getChapterWeight());
                    chapterVo.setUuid(courseChapter.getChapterUuid());
                    return chapterVo;
                })).entrySet().stream().map(entry -> {
                    List<DxSeriesCourseChapter> child = entry.getValue();
                    List<DxSeriesCourseLessonVo> transformedList = child.stream().map(item -> {
                        DxSeriesCourseLessonVo lessonVo = new DxSeriesCourseLessonVo();
                        lessonVo.setId(item.getId());
                        lessonVo.setTitle(item.getLessonTitle());
                        lessonVo.setUuid(item.getLessonUuid());
                        lessonVo.setWeight(item.getLessonWeight());
                        lessonVo.setTenantId(item.getTenantId());
                        lessonVo.setLessonCourseId(item.getLessonCourseId());
                        return lessonVo;
                    }).collect(Collectors.toList());
                    DxSeriesCourseChapterVo key = entry.getKey();
                    key.setChildren(transformedList);
                    return key;
        }).collect(Collectors.toList());
        logger.info(JSON.toJSONString(chapters, true));