QueryDslMongoRepository Projection

I am using spring-data for mongodb with querydsl. I have a repository

public interface DocumentRepository extends MongoRepository<Document, String> ,QueryDslPredicateExecutor<Document> {}

and an entity

@QueryEntity
public class Document {

private String id;
private String name;
private String description;
private boolean locked;
private String message;

}

I need to load a list of documents with id and name informations. So only id and name should be loaded and set in my entity. I think query projection is the right word for it. Is this supported?

In addition I need to implement some lazy loading logic. Is there anything like "skip" and "limit" features in a repository?

According to the Answer of this -> Question <- I implemeted following solution.

Entity

@QueryEntity
public class Document extends AbstractObject {
}

Custom QuerydslMongoRepository

public interface CustomQuerydslMongoRepository<T extends AbstractObject,ID extends Serializable> extends MongoRepository<T, ID> ,QueryDslPredicateExecutor<T>{
    Page<T> findAll(Predicate predicate, Pageable pageable,Path... paths);
    Page<T> findAll(Predicate predicate, Pageable pageable,List<Path> projections);

}

Custom QuerydslMongoRepository Implementation

public class CustomQuerydslMongoRepositoryImpl<T extends AbstractObject,ID extends Serializable> extends QueryDslMongoRepository<T,ID> implements CustomQuerydslMongoRepository<T,ID> {

    //All instance variables are available in super, but they are private
    private static final EntityPathResolver DEFAULT_ENTITY_PATH_RESOLVER = SimpleEntityPathResolver.INSTANCE;


    private final EntityPath<T> path;
    private final PathBuilder<T> pathBuilder;
    private final MongoOperations mongoOperations;
    public CustomQuerydslMongoRepositoryImpl(MongoEntityInformation<T, ID> entityInformation, MongoOperations mongoOperations) {
        this(entityInformation, mongoOperations,DEFAULT_ENTITY_PATH_RESOLVER);
    }

    public CustomQuerydslMongoRepositoryImpl(MongoEntityInformation<T, ID> entityInformation, MongoOperations mongoOperations, EntityPathResolver resolver) {
        super(entityInformation, mongoOperations, resolver);
        this.path=resolver.createPath(entityInformation.getJavaType());
        this.pathBuilder = new PathBuilder<T>(path.getType(), path.getMetadata());
        this.mongoOperations=mongoOperations;
    }

    @Override
    public Page<T> findAll( Predicate predicate, Pageable pageable,Path... paths) {
        Class<T> domainType = getEntityInformation().getJavaType();
        MongodbQuery<T> query = new SpringDataMongodbQuery<T>(mongoOperations, domainType);
        long total = query.count();
        List<T> content = total > pageable.getOffset() ? query.where(predicate).list(paths) : Collections.<T>emptyList();
        return new PageImpl<T>(content, pageable, total);
    }

    @Override
    public Page<T> findAll(Predicate predicate, Pageable pageable, List<Path> projections) {
        Class<T> domainType = getEntityInformation().getJavaType();
        MongodbQuery<T> query = new SpringDataMongodbQuery<T>(mongoOperations, domainType);
        long total = query.count();
        List<T> content = total > pageable.getOffset() ? query.where(predicate).list(projections.toArray(new Path[0])) : Collections.<T>emptyList();
        return new PageImpl<T>(content, pageable, total);
    }
}

Custom Repository Factory

public class CustomQueryDslMongodbRepositoryFactoryBean<R extends QueryDslMongoRepository<T, I>, T, I extends Serializable> extends MongoRepositoryFactoryBean<R, T, I> {


    @Override
    protected RepositoryFactorySupport getFactoryInstance(MongoOperations operations) {
        return new CustomQueryDslMongodbRepositoryFactory<T,I>(operations);
    }

    public static class CustomQueryDslMongodbRepositoryFactory<T, I extends Serializable> extends MongoRepositoryFactory {
        private MongoOperations operations;

        public CustomQueryDslMongodbRepositoryFactory(MongoOperations mongoOperations) {
            super(mongoOperations);
            this.operations = mongoOperations;
        }


        @SuppressWarnings({ "rawtypes", "unchecked" })
        protected Object getTargetRepository(RepositoryMetadata metadata) {
                return new CustomQuerydslMongoRepositoryImpl(getEntityInformation(metadata.getDomainType()), operations);
          }

        protected Class<?> getRepositoryBaseClass(RepositoryMetadata metadata) {
            return CustomQuerydslMongoRepository.class;
        }
    }
}

Entity Repository

public interface DocumentRepository extends CustomQuerydslMongoRepository<Document, String>{

}

Usage in Service

@Autowired
DocumentRepository repository;

public List<Document> getAllDocumentsForListing(){
return repository.findAll(  QDocument.document.id.isNotEmpty().and(QDocument.document.version.isNotNull()), new PageRequest(0, 10),QDocument.document.name,QDocument.document.version).getContent();
}