Problem with mongo AddFieldsOperation in java

Question

I have to filter documents by multiple fields using regex (text searching, but mongo text indexes don't allow partial search)

Everything works fine when I make big OR Criteria

    Criteria().orOperator(
            Criteria.where(fieldOne).regex(search, caseInsensitive),
            Criteria.where(fieldTwo).regex(search, caseInsensitive),
            ..

But probably this could be made smoother if I used: https://docs.mongodb.com/manual/reference/operator/aggregation/addFields/

My problem is when I trying to use this in java like that:

Aggregation.addFields()
        .addField("\$fullText")
        .withValueOfExpression("\$concat", fieldOne, fieldTwo, ..

MongoTemplate sees only first param from above function MongoTemplate : Executing aggregation: [{ "$addFields" : { "fullText" : "$concat"}},

Funny because if I write this like that:

        .addField("\$fullText")
        .withValueOfExpression(fieldOne, fieldTwo, "\$concat", ..

It returns me result filtered only by fieldOne and query looks like that: MongoTemplate : Executing aggregation: [{ "$addFields" : { "fullText" : "$fieldOne"}},

Did anyone have similar problem? Thanks in advance for any help :)