Instead of using Hibernate Search 5 APIs, get a org.hibernate.search.mapper.orm.session.SearchSession
using org.hibernate.search.mapper.orm.Search#session(org.hibernate.Session),
create a SearchQuery with org.hibernate.search.mapper.orm.session.SearchSession#search(Class),
and define your projections using SearchQuerySelectStep.select(Function).
org.hibernate.search.mapper.orm.session.SearchSessionusingorg.hibernate.search.mapper.orm.Search#session(org.hibernate.Session), create aSearchQuerywithorg.hibernate.search.mapper.orm.session.SearchSession#search(Class), and define your projections usingSearchQuerySelectStep.select(Function).