Java 计算关系总数并将其映射到结果

给定

Post

将文档类型设置为：

@Getter
@AllArgsConstructor
class Post {
    String publisher;
    Set<String> interests;
}

---

要将该操作与实现进行比较，我将按照以下方法进行查找：

Set<Result> buildQuery(List<Post> postList) {
    return postList.stream()
            .flatMap(post -> post.getInterests().stream()
                    .map(interest -> new AbstractMap.SimpleEntry<>(interest, post.getPublisher())))
            .collect(Collectors.groupingBy(Function.identity(), Collectors.counting()))
            .entrySet().stream()
            .map(e -> new Result(e.getKey().getKey(), e.getKey().getValue(), e.getValue()))
            .collect(Collectors.toSet());
}

这将导致以下文件：

{
    "_id" : {
        "interestId" : "INTEREST1",
        "publisherId" : "PUBLISHER2"
    },
    "count" : 3.0
}

现在，我正在努力解决end

map

操作，以将其表述为一个预期结果，即：

{
    "_id" : ...
    "interestId" : "INTEREST1",
    "publisherId" : "PUBLISHER2"
    "count" : 3.0
}

如何修复查询以获得预期结果？

相当于Java的映射：

db.posts.aggregate([
    {"$unwind" :"$interestIds"},
    {"$group" : {"_id": {interestId: "$interestIds", publisherId:"$publisherId"}, "count": {"$sum" : 1}}},
    {"$project":{ _id: 0, interestId: "$_id.interestId", publisherId: "$_id.publisherId", count: 1 }}
]);

是Java地图的等价物：

db.posts.aggregate([
    {"$unwind" :"$interestIds"},
    {"$group" : {"_id": {interestId: "$interestIds", publisherId:"$publisherId"}, "count": {"$sum" : 1}}},
    {"$project":{ _id: 0, interestId: "$_id.interestId", publisherId: "$_id.publisherId", count: 1 }}
]);

db.posts.aggregate([
    {"$unwind" :"$interestIds"},
    {"$group" : {"_id": {interestId: "$interestIds", publisherId:"$publisherId"}, "count": {"$sum" : 1}}},
    {"$project":{ _id: 0, interestId: "$_id.interestId", publisherId: "$_id.publisherId", count: 1 }}
]);