Spring Data Mongo-查询方法和不同字段

Question

I'm currently working on a project using Spring Data Mongo. My repository is just an interface extending MongoRepository. I would like to add a custom query method in order to retrieve all distinct values for one of my collection's fields.

I tried something like this:

@RepositoryRestResource(path = "devices", collectionResourceRel = "deviceInfos")
public interface DeviceInfoRepository extends MongoRepository<DeviceInfo, String> {

    @RestResource(path = "distinctUnitIds")
    List<String> findDistinctUnitIdBy();

}

With that code, Spring give me an error because it's not able to build my list. So I tried this:

@RepositoryRestResource(path = "devices", collectionResourceRel = "deviceInfos")
public interface DeviceInfoRepository extends MongoRepository<DeviceInfo, String> {

    @RestResource(path = "distinctUnitIds")
    List<DeviceInfo> findDistinctUnitIdBy();

}

That code works but the distinct seems to be totally ignored.

The documentation about Distinct in query method is really not clear...

Did I do something wrong? What's the best way to solve get the distinct values of a field using Spring Data?

Thanks!

Answer 1

You will have to use Spring Data MongoTemplate - the MongoRepository interfaces are made only for basic functionality and for more fine grain control of what you are querying, its best to use MongoTemplate .

Here is an example of how one would get distinct values from a collection:

Criteria criteria = new Criteria();
criteria.where("dataset").is("d1");
Query query = new Query();
query.addCriteria(criteria);
List list = mongoTemplate.getCollection("collectionName")
    .distinct("source",query.getQueryObject());

Here is the link to more info: mongodb mongoTemplate get distinct field with some criteria

Answer 2

in SpringBoot2 you can do the following :

DistinctIterable<String> iterable = mongoTemplate.getCollection(COLLECTION_NAME).distinct("source",in(FieldValue,query.getQueryObject(), String.class);
        MongoCursor<String> cursor = iterable.iterator();
        List<String> list = new ArrayList<>();
        while (cursor.hasNext()) {
            list.add(cursor.next());
        }
        return list;