Spring Data for MongoDB aggregation query

Question

I'm struggling with translating this mongoDB query in Spring Data MongoDB:

db.applicates.aggregate(
   [
   {
      "$match": {
        "claimantCategory": 1
      }
    },
      {
        $group : {
           _id : { month: { $month: "$claimDate" }, day: { $dayOfMonth: "$claimDate" }, year: { $year: "$claimDate" } },
       count: { $sum: 1 }
    }
  }
   ]
)

I've tryed this:

TypedAggregation<Applicate> aggregation = newAggregation(Applicate.class,
            match(Criteria.where("claimantCategory").is(claimantCategory)),
            project("claimDate")
                    .andExpression("dayOfMonth("+"\""+"claimDate"+"\""+")").as("day")
                    .andExpression("month(claimDate)").as("month")
                    .andExpression("year(claimDate)").as("year"),
            group(fields().and("day").and("month").and("year"))
                    .count().as("count"));
AggregationResults<ClaimsAggregator> groupResults = mongoOperations.aggregate(aggregation, ClaimsAggregator.class);

But it fails with exception : can't convert from BSON type String to Date

My Applicate.class:

public class Applicate {

@Id
private String id;

private int claimId;

@DateTimeFormat (iso = DateTimeFormat.ISO.DATE)
private Date claimDate;

private int codeOfForm;
private String claimStatus;
private String fio;
private int claimantCategory;
private int serviceCode;
private String subserviceName;
private String departmentName;
//getter,setters, constructor
}

ClaimsAggregator.class:

public class ClaimsAggregator {
private String claimDate;
private int count;
....
}

Replace the line .andExpression("dayOfMonth("+"\""+"claimDate"+"\""+")").as("day") with this .andExpression("dayOfMonth(claimDate)").as("day"). — chridam
– chridam, Commented Nov 23, 2015 at 12:56
@chridam, thanks for suggestion. Just tested that and now it returns null in date field. What may cause that? — MoOFueL
– MoOFueL, Commented Nov 23, 2015 at 13:02
Not too sure, might be some documents which don't have the claimDate field? — chridam
– chridam, Commented Nov 23, 2015 at 13:04

MoOFueL · Accepted Answer · 2015-11-23 13:17:47Z

I've found an answer! as @chridam suggested, u need to replace the line

.andExpression("dayOfMonth("+"\""+"claimDate"+"\""+")").as("day")

with this

.andExpression("dayOfMonth(claimDate)").as("day")

Now you need to add

.first("claimDate").as("claimDate")

to line

group(fields().and("day").and("month").and("year"))

Final code:

TypedAggregation<Applicate> aggregation = newAggregation(Applicate.class,
            match(Criteria.where("claimantCategory").is(claimantCategory)),
            project("claimDate")
                    .andExpression("dayOfMonth(claimDate)").as("day")
                    .andExpression("month(claimDate)").as("month")
                    .andExpression("year(claimDate)").as("year"),
            group(fields().and("day").and("month").and("year")).first("claimDate").as("claimDate")
                    .count().as("count"));

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