Is it possible to combine an entity with aggregate query results?
example :
Criteria userCrit = session.createCriteria(Topic.class);

userCrit.createAlias("userTopics", "userTopics");
userCrit.createAlias("userTopics.user", "user");

userCrit.setProjection(Projections.count("user.userId").as("numInterested"));
userCrit.setProjection(Projections.groupProperty("topicId"));

This query should include all attributes of Topic class plus the count value using the group by clause

I never tried such thing but I think,
if it is possible at all, then by implementing and using a custom result-transformer