Append QueryDSL 谓词或基于过滤器值构建谓词

Question

I'm new to Querydsl and Im looking for a way to append/build predicate based on filters. You can see in the example that if one of the fields in the filter doesn't have value it shouldn't go in predicate.

If something like this is not possible, what is the best approach then?

For example filter (GetPaintingRequest) contains these fields (there are more in the filter, but not important):

public class GetPaintingsRequest {
    private String author;
    private Integer style;
    private String paintingName;

    //.....getters and setters
}

So in a service class I want to filter painting like this

public List<Painting> getFilteredPaintings(GetPaintingsRequest request) {
        
        QPainting painting = QPainting.painting;
        
        //predicate for all paintings that are not deleted and not sold
        Predicate query = painting.deleted.isFalse().and(painting.isSold.isFalse());
        
        if (!request.getAuthor().equals("")) {
            //append to existing predicate name of the author
            query.and.painting.autor.eq(request.getAuthor()); //obviously not working - just as an example what I want
            
        }

        if (!request.getPaintingName().equals("")) {
            //append to existing predicate painting name
            query.and.painting.paintingName.eq(request.getPaintingName()); //obviously not working - just as an example what I want
        }
        
        var paintingList = paintingRepository.findAll(query);

}

Answer 1

I've found a solution!

QPainting painting = QPainting.painting;
        
        BooleanBuilder booleanBuilder = new BooleanBuilder();
        
        booleanBuilder.and(painting.deleted.isFalse().and(painting.isSold.isFalse()));      
        

        if (!request.getAuthor().equals("")) {
            booleanBuilder.and(painting.author.eq(request.getAuthor()));

        }

        if (!request.getPaintingName().equals("")) {
            booleanBuilder.and(painting.paintingName.eq(request.getPaintingName()));
        }
        
        
        
        Predicate predicate = booleanBuilder;
        var paintingList = paintingRepository.findAll(predicate);