SpringData mongoDB API for Aggregation $map

Question

Following is my Native MongoDB query and below is the SpringData Mongo API equivalent. I am getting struck on using $map in $project in SpringData Mongo API. Appreciate your help on completing my conversion to API

db.users.aggregate([    
    { $match: {$and : [{userType:"200"} },    
     { $unwind: "$userOrgMap" },
    {
      $lookup:
        {
          from: "users",
          localField: "userOrgMap.createdbyuser",
          foreignField: "_id",
          as: "created_by"
        }
   },
   {$project:{
       _id:"$_id",
       login:"$login",
       firstName:"$firstName",
       lastName:"$lastName",
       email:"$email",
       deactivateFlag:"$deactivateFlag",
       createdOn:"$createdOn",
       createdBy:{
        "$map": { 
                    "input": "$created_by", 
                    "as": "u", 
                      "in": { 
                          "name": { "$concat" : [ "$$u.firstName", " ", "$$u.lastName" ] }, 
                      } 
                }
    }
      }
    },
    { $sort : { createdBy : 1} }

])

Spring Query

 Aggregation aggregation = newAggregation(
            Aggregation.match(Criteria.where("userType").is(userType)),
            Aggregation.unwind("userOrgMap"),
            Aggregation.lookup("users", "userOrgMap.createdbyuser", "_id", "created_by"),
            Aggregation.project("userId","login","firstName","lastName","email","deactivateFlag","createdOn")
        );

Possible duplicate of Filter array in sub-document array field in Spring framework — s7vr
– s7vr, Commented May 13, 2017 at 11:22
Thanks for info. But I need some more help to figure out the API . My requirement is different. Aggregation.project("userId","login","firstName","lastName","email","deactivateFlag","createdOn") .and(mapItemsOf("created_by").as("u"). ??? )).as("createdBy") — karmaker
– karmaker, Commented May 13, 2017 at 11:40

s7vr · Accepted Answer · 2017-05-13 14:30:10Z

4

You can try below $map aggregation.

  project().and(mapItemsOf("created_by").
                            as("u").
                            andApply(new AggregationExpression() {
                                @Override
                                public DBObject toDbObject(AggregationOperationContext aggregationOperationContext) {
                                    return new BasicDBObject("name", StringOperators.valueOf("u.firstName").concat(" ").concatValueOf("u.lastName").toDbObject(aggregationOperationContext));
                                }
                            }))
             .as("createdBy");

Using $let expression

 project().and(VariableOperators.Let.define(VariableOperators.Let.ExpressionVariable.newVariable("u").forExpression(ArrayOperators.arrayOf("created_by").elementAt(0))).
                            andApply(new AggregationExpression() {
                                @Override
                                public DBObject toDbObject(AggregationOperationContext aggregationOperationContext) {
                                    return new BasicDBObject("name", StringOperators.valueOf("u.firstName").concat(" ").concatValueOf("u.lastName").toDbObject(aggregationOperationContext));
                                }
                            }))
            .as("createdBy");

Use lambda and static imports.

import static org.springframework.data.mongodb.core.aggregation.ArrayOperators.arrayOf;
import static org.springframework.data.mongodb.core.aggregation.StringOperators.valueOf;
import static org.springframework.data.mongodb.core.aggregation.VariableOperators.Let.ExpressionVariable.*;
import static org.springframework.data.mongodb.core.aggregation.VariableOperators.Let.define;
import static org.springframework.data.mongodb.core.aggregation.VariableOperators.mapItemsOf;

project().and(mapItemsOf("created_by").
                as("u").
                andApply(aggregationOperationContext -> new BasicDBObject("name", valueOf("u.firstName").concat(" ").concatValueOf("u.lastName").toDbObject(aggregationOperationContext))))
                .as("createdBy");

    project().and(define(newVariable("u").forExpression(arrayOf("created_by").elementAt(0))).
            andApply(aggregationOperationContext -> new BasicDBObject("name", valueOf("u.firstName").concat(" ").concatValueOf("u.lastName").toDbObject(aggregationOperationContext))))
            .as("createdBy");

edited May 13, 2017 at 14:30

answered May 13, 2017 at 11:57

s7vr

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14 Comments

karmaker Over a year ago

Appreciate your quick reply.But I am getting "as" as undefined

s7vr Over a year ago

Np. Updated answer to include the name alias for you to use map. I can't see anything in the api to provide the alias in the nested expression. So I have utilize BasicDBObject to create expression. You can do this with $let operator too by using $arrayElemAt and $concat.

karmaker Over a year ago

Just realised that the result is not same for the created by. I am getting the following [{"userId":"249840105","login":"km993v","firstName":"Karthikeyan","lastName":"Maruthamuthu","createdOn":"2017-03-02 14:11:58.775","email":"[email protected]","deactivateFlag":false,"createdBy":"[ \"Chithra Nattamai Subburaman\"]"}] I am expecting the following "createdBy" : [ { "name" : "kaushik Mehta" } ]

s7vr Over a year ago

Do you mean it is missing name field ? from the output ? Yes, I've mentioned that in my second comment. Please use the latest code. It will work.

karmaker Over a year ago

My requirement is to have createdBy as an additional field with the concat of firstName and lastName. I heard of addField usage in aggregation. But not sure how to use it to achieve. If having createdBy is not possible without array, I am fine. But I don't want "[ \" from the output. Because in the output , I am getting "[" as a string value and not taken as array. I would prefer to get the same output as I got for my native query. Pls help

|

Divya Gopal · Accepted Answer · 2019-12-31 20:35:53Z

2

This is another approach I was able to do this.

Aggregation.project("userId","login","firstName","lastName","email","deactivateFlag","createdOn").and(VariableOperators.Map.itemsOf("created_by").as("u").andApply(StringOperators.Concat.valueOf("$$u.firstName").concat(" ").concatValueOf("$$u.lastName"))).as("createdBy");

answered Dec 31, 2019 at 20:35

Divya Gopal

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