Projection usage in new morphia [2.x]

[arivazhagan-jeganathan]

In Old morphia, 1.x i could build project pipeline in aggregate query like this:

_id:{fieldA:"text1", "fieldB":"text2} --> this section is built as part of Group pipeline operation.
{"$project": {"_id": "$null", "fieldA": "$_id.fieldA", "fieldB": "$_id.fieldB", "fieldC": 1}}]

How do build a similar Projection query with new Morphia (2.x)?
with code like
project(Projection.project().include("_id").include("fieldA").include("fieldB").include("fieldC")) -->

{"$project": {"_id": true, "fieldA": true, "fieldB": true, "fieldC": true}}
]);

Unable to build a customized project pipeline as explained above. Kindly suggest a way to do this.

[evanchooly]

Can you show me the code you're trying to use? I think I can guess reasonably close but I'd rather not make assumptions if I can help it. Old and new code would be ideal so I can see what you were doing vs how you're trying to do so now. Thanks.

[arivazhagan-jeganathan]

Old Code:
imports:
import static dev.morphia.aggregation.Group.grouping;
import static dev.morphia.aggregation.Projection.projection;

public List<TestEntity> getTestEntityPage(Criteria criteria) {
  Query<TestEntity> query = baseDao.getQueryByCriteria(criteria, false, true);
          Iterator<TestEntity> it = prepareTestEntityQuery(query)
                  .project(
                          projection("_id", "null"),
                          projection("fieldA", "_id.fieldA"),
                          projection("fieldB", "_id.fieldB"),
                          projection("fieldC")
                  )
                  .aggregate(TestEntity.class);
  return safeStream(it).collect(toList());
}

private AggregationPipeline prepareTestEntityQuery(Query<TestEntity> query) {
        return getDatastore().createAggregation(TestEntity.class)
                .sort(Sort.ascending("startTime"))
                .group(
                        asList(
                                grouping("fieldA", "fieldA"),
                                grouping("fieldB", "fieldB")),
                        grouping("fieldC", new Accumulator("$last", "fieldC")),
                        grouping("fieldA", new Accumulator("$last", "fieldA")),
                        grouping("fieldD", new Accumulator("$last", "fieldD")),
                        grouping("fieldE", new Accumulator("$last", "fieldE")))
                .match(query);
}

New Code

public List<TestEntity> getTestEntityPage(Criteria criteria) {
        Iterator<TestEntity> it = prepareTestEntityQuery(baseDao.getFilterByCriteria(criteria, false, true))
                .project(Projection.project().include("_id").include("fieldA").include("fieldB").include("fieldC"))
                .execute(TestEntity.class);

        return safeStream(it).collect(toList());
    }

private Aggregation<TestEntity> prepareTestEntityQuery(List<Filter> filter) {
        
        Aggregation<TestEntity> aggregates =  getDatastore().aggregate(TestEntity.class)
                .group(Group.group(Group.id()
                                    .field("fieldA")
                                    .field("fieldB"))
                            .field("fieldC",new Expression("$last", "$fieldC"))
                            .field("fieldD", new Expression("$last", "$fieldD"))
                            .field("fieldE", new Expression("$last", "$fieldE"))
                            .field("fieldF", new Expression("$last", "$fieldF")))
                .sort(dev.morphia.aggregation.experimental.stages.Sort.sort().ascending("startTime"));
              return aggregates.match(filter.toArray(new Filter[0]));    
    }

Help replicate the query built using old code using New Morphia (2.x)