CODEWITHSUNDEEP
javamongodbmongodb-queryaggregation-frameworkspring-data-mongodb
Sandeep
Sandeep

Reputation: 243

Spring data mongo aggregation with @Field annotation

I have requirement to perform group by on nested fields in mongo. The second level nested field is annotated with @Field. I am using projection with groupBy. Example

ProjectionOperation projectionOperation = Aggregation.project("id")
            .and("author.eid").as("user");
GroupOperation groupOperation = Aggregation.group(aggregationBy, "user").count().as("total");
Aggregation aggregation =
        Aggregation.newAggregation(projectionOperation groupOperation);
AggregationResults<Document> aggregationResults = myRepository.getMongoTemplate().aggregate(aggregation, MyClass.class, Document.class);

On execution I am getting error "org.springframework.data.mapping.PropertyReferenceException: No property eid found for type User!"

public class MyClass {
 User author;
}
public class User {
 @Field("eid")
 @JsonProperty("eid") // fasterxml
 public String externalId;
}

What I can think of is when casting the aggregation result to MyClass, it is unable to find "eid" because it is annotated.

How to handle this usecase ?

Upvotes: 1

Views: 5356

Answers (1)

s7vr
s7vr

Reputation: 75934

The @Field annotation parsed to replace the pojo property with the field name.

So you should be using

ProjectionOperation projectionOperation = Aggregation.project("id")
            .and("author.externalId").as("user");

the query generated will be

{ "$project" : { "user" : "$author.eid" }

Upvotes: 4

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