java - How to use MongoDB $let with Spring-Data? -

i have mongodb collection of places. typical place has of following fields:

{ "_id" : objectid("575014dc6b028f07bef53681"), "_class" : "domain.model.placev1", "name" : "Γιασεμί", "primary_photo_url" : "https://irs0.4sqi.net/img/general/original/34666238_sthsh6chic7hpaub4rztrvg6cfc5ylfi15arar7zuuq.jpg", "seendetails" : numberlong(0), "foursquare_checkins" : 646, "foursquare_tips" : 28, "keywords" : [      "" ], "verified" : 1, "location" : {     "loc" : {         "type" : "point",         "coordinates" : [              25.898318,              36.831486         ]     },     "formattedaddress" : "Χώρα",     "locality" : "amorgos",     "first_neighbourhood" : "katapola",     "greek_locality" : "Αμοργός",     "greek_first_neighbourhood" : "Κατάπολα" }, "contact" : {     "phone_numbers" : [          "+30 2285 074017"     ] }, "price" : {     "pricevotes" : numberlong(0),     "price" : 0,     "pricevotessum" : numberlong(0) }, "rating" : {     "rating" : 8,     "ratingvotes" : numberlong(0),     "ratingvotessum" : numberlong(0) }, "categories" : [      {         "cat_id" : numberlong(10310061000),         "category" : "café",         "greek_category" : "Καφετέρια",         "weight" : 4     },      {         "cat_id" : numberlong(11610021000),         "category" : "bar",         "greek_category" : "Μπαρ",         "weight" : 4     } ] } 

i want make queries sorting based on score result of expressions , conditions. mongo shell have tried this:

db.place.aggregate([ {$match:{"location.locality":"athens"}},  {$project:     {name:1, location:1, score:{                               $let: {                                      vars:{ foursquare: {                                      $cond: { if: { $gte: [ "$foursquare_checkins", 500 ] }, then: 500, else: "$foursquare_checkins" }                                     },                         rating: {$multiply:["$rating.rating", 100]},                         },                  in:{$add:["$$foursquare", "$$rating", "$seendetails"]}                             }                  }                      } }, {$sort: {score: -1}}]).pretty(); 

this simple example of queries. score contain more complex expressions distance location. problem cannot find way use $let , $cond operator in java code spring. help?

you should able using nested dbobject , custom aggregation operation.

for example:

map operations = new hashmap(); operations.put("name", 1); operations.put("location", 1); operations.put("score", new basicdbobject("$let", new basicdbobject("vars", new basicdbobject()))); 

then can create customaggregationoperation add project

customaggregationoperation project = new customaggregationoperation(new basicdbobject("$project", operation)); 

this give following pipeline:

{ "$project" : { "score" : { "$let" : { "vars" : { }}} , "name" : 1 , "location" : 1}} 

then can add other stages:

aggregation aggregate = aggregation.newaggregation(match, project, sort); 

---

public class customaggregationoperation implements aggregationoperation {     private dbobject operation;      public customaggregationoperation (dbobject operation) {         this.operation = operation;     }      @override     public dbobject todbobject(aggregationoperationcontext context) {         return context.getmappedobject(operation);     } }