Hi Alejandro,
I have a kids training attendance list which pick up data from the database if the child was present or not. The data is formed from two entities (Member.class and Training.class) that work very well.
Do you think will work with your report tool?
List<Training> trainings = trainingRepository.findAll);
for (Training training : trainings) {
grid.addColumn(member -> training
.getMember()
.contains(member) ? "X" : "")
.setHeader(training.getTrainingdate().format(formatter));