Java& Mongo:获取存在字段的对象 [英] Java&Mongo: get object where field exist

问题描述

情况: 我收集了文档，每个文档都包含以下字段:"_ id"(ObjectId)，"userId"(String)，但也可以是字段"files"(Object).

Situation: I have collection with documents, each document contains such fields: "_id"(ObjectId), "userId"(String), but it also can be field "files"(Object).

当我这样做时:

final Query query = new Query();           
query.fields().include("_id");           

final List<File> fileList = mongo.find(query, File.class);

结果我得到了所有记录的fileList，这很好.

As a result I'm getting fileList with all records and that is fine.

但是当我这样做时，仅在文件"字段存在的地方获取记录-结果是错误的.

But when I'm doing like that, to get records only where "files" field exists - result is error.

final Query query = new Query();           
query.fields().include("files");           

final List<File> fileList = mongo.find(query, File.class);

是否由于尝试获取对象"字段而发生错误?以及如何使用查询或条件解决这个问题?

Does error occur because I'm trying to get Object field? And how I can solve this with Query or Criteria?

推荐答案

您可以构造此Query来获取包含files的所有文档:

You can construct this Query to get all documents that contains files filed:

Query.query(Criteria.where("files").exists(true))

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