Message Title

FullTextEntityManager fullTextEntityManager = Search.getFullTextEntityManager( entityManager );

FullTextSearchTarget<Book> target = fullTextEntityManager.search( Book.class );

FullTextQuery<MyProjectionBean> query = target.query()
                .asProjection( f ->
                                 f.composite(
                                                MyProjectionBean::new,
                                                f.field( "id_stored", Long.class )
                                                f.field( "title", String.class )
                                ).toProjection()
                )
                .predicate( f -> f.match()
                        .onFields( "title", "authors.name" )
                        .matching( "Refactoring: Improving the Design of Existing Code" )
                        .toPredicate()
                )
                .sort( f -> f.sort()
                        .byField( "title" ).asc()
                        .then().byField( "subtitle" ).asc()
                        .toSort()
                )
                .build();

List<MyProjectionBean> result = query.getResultList();

We could try to improve on that.
One idea would be to remove the need to call the toPredicate, toProjection and toSort methods even at the top level:

FullTextEntityManager fullTextEntityManager = Search.getFullTextEntityManager( entityManager );

FullTextSearchTarget<Book> target = fullTextEntityManager.search( Book.class );

FullTextQuery<MyProjectionBean> query = target.query()
                .asProjection( f -> f.composite(
                                                MyProjectionBean::new,
                                                f.field( "id_stored", Long.class )
                                                f.field( "title", String.class )
                 ) )
                .predicate( f -> f.match()
                        .onFields( "title", "authors.name" )
                        .matching( "Refactoring: Improving the Design of Existing Code" )
                )
                .sort( f -> f.sort()
                        .byField( "title" ).asc()
                        .then().byField( "subtitle" ).asc()
                )
                .build();

List<MyProjectionBean> result = query.getResultList();

That would, however, remove the ability to returned a cached SearchPredicate/SearchProjection/SearchSort object from the lambda: the lambda would be expected to return a Search(Predicate/Projection/Sort)TerminalContext.

Maybe we should add a method to the DSL to convert a SearchPredicate/SearchProjection/SearchSort to a Search(Predicate/Projection/Sort)TerminalContext? Something like f.from(searchPredicate)? If we do that, it could make sense to change the naming around SearchPredicate/SearchProjection/SearchSort: we could make it more obvious that these are mainly for re-use, and are not really necessary if you don't cache them. Maybe rename them to ReusablePredicate, or something similar?