带有@Field批注的Spring数据mongo聚合

Question

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 ?

Answer 1

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" }