如何使用 $toLower 和 $trim 聚合运算符使用 MongoDB Java？

Question

I have a collection called Users, which contains an array called skills.

I use the following code to unwind the skills array and count the number of documents associated with each skill:

Bson uw = unwind("$skills");
Bson sbc = sortByCount("$skills");
Bson limit = limit(10);
coll.aggregate(Arrays.asList(uw, sbc,limit)).forEach(printDocuments());

Now I want to make use of $trim and $toLower operations for the above aggregation because in the database, some skills saved in different ways (eg, "CSS" , "CSS " , and "css" ).

I'm able to do this in the mongo shell with the following aggregation:

db.users.aggregate([{$unwind:"$skills"} , {$sortByCount:{$toLower:{$trim:{input:"$skills"}}}}])

But I'm having troubles with implementing it in Java.

Do you have any idea?

Answer 1

I managed to find a way to do this with changing the sortByCount to the following:

Bson sbc = sortByCount(eq("$toLower", eq("$trim", eq("input", "$skills"))));