Limit search by id - spring

Question

I want to implement an endpoint which is used to search into table limited by class_id:
Table:
#Entity
#Table(name = "class_items")
public class ClassItems implements Serializable {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "id", unique = true, updatable = false, nullable = false)
private int id;
#Column(name = "class_id", length = 20)
private Integer classId;
#Column(name = "title", length = 75)
private String title;
}
#PostMapping("/{class_id}/find")
public Page<ClassCategoriesFullDTO> search(#PathVariable("class_id") Integer classId, #Valid ClassCategoriesSearchParams params, Pageable pageable) {
Page<ClassCategoriesFullDTO> list = classItemsRestService.findClassItemsByClassId(classId, params, pageable);
return list;
}
public Page<ClassCategoriesFullDTO> findClassItemsByClassId(Integer classId, ClassCategoriesSearchParams params, Pageable pageable) {
// Limit here queries by classId
Specification<Product> spec = (root, query, cb) -> {
List<Predicate> predicates = new ArrayList<>();
if (params.getTitle() != null) {
predicates.add(cb.equal(root.get("title"), params.getTitle()));
}
return cb.and(predicates.toArray(new Predicate[predicates.size()]));
};
return classItemsService.findAllByClassId(spec, pageable).map(classItemsMapper::toFullDTO);
}
#Service
#Transactional
public class ClassItemsServiceImpl implements ClassItemsService {
#PersistenceContext
private EntityManager entityManager;
private ClassItemsRepository dao;
#Autowired
public ClassItemsServiceImpl(ClassItemsRepository dao) {
this.dao = dao;
}
public Page<ClassItems> findAllByClassId(Specification spec, Pageable pageable) {
return this.dao.findAllByClassId(spec, pageable);
}
}
#Repository
public interface ClassItemsRepository extends JpaRepository<ClassItems, Long>, JpaSpecificationExecutor<ClassItems> {
Page<ClassItems> findAllByClassId(Specification spec, Pageable pageable);
}
I get error:
Parameter value [org.service.ClassItemsRestServiceImpl$$Lambda$1987/0x0000000801e21440#3c4de5a9] did not match expected type [java.lang.Integer (n/a)]; nested exception is java.lang.IllegalArgumentException: Parameter value [org.service.ClassItemsRestServiceImpl$$Lambda$1987/0x0000000801e21440#3c4de5a9] did not match expected type [java.lang.Integer (n/a)]",
Do you know how I can solve this issue?

Answer 1

You're getting this error because Spring Data is trying to generate a query based on the method name findAllByClassId, and so it expects an integer as the first parameter.
When working with specifications, you're supposed to use the methods provided by JpaSpecificationExecutor. Adding your own methods with specifications as parameters won't work. If you want to filter by classId, append the appropriate filter to the specification itself.
EDIT the solution is to add the extra condition when constructing the specification:
Specification<Product> spec = (root, query, cb) -> {
List<Predicate> predicates = new ArrayList<>();
if (params.getTitle() != null) {
predicates.add(cb.equal(root.get("title"), params.getTitle()));
}
predicates.add(cb.equal(root.get("classId"), classId));
return cb.and(predicates.toArray(new Predicate[predicates.size()]));
};
and then, in ClassItemsServiceImpl, call dao.findAll(spec)