Building Queries with Spring Data JPA - Spring Data - page 68

JPA Criteria API
In order to build queries with the JPA Criteria API, the ContactRepository interface
must extend the JpaSpecificationExecutor<T> interface. This gives us access to
the Page<Contact> findAll(Specification spec, Pageable page) method that
can be used to paginate the query results of criteria queries. The only thing that is left
for us to do is to modify the search() method of the RepositoryContactService
class. Our implementation is explained as follows:

1. We get the used specification.
2.

We get the used PageRequest object.

3. We get the Page implementation by calling the repository method and

passing the specification and the PageRequest object as a parameter.

4. We return the requested list of contacts by calling the getContent() method

of the Page class.

The source code of our search method is given as follows:

@Transactional(readOnly = true)
@Override
public List<Contact> search(SearchDTO dto) {
Specification<Contact> contactSpec =
firstOrLastNameStartsWith(dto.getSearchTerm());
Pageable pageSpecification = buildPageSpecification(dto.
getPageIndex(), dto.getPageSize());

Page<Contact> page = repository.findAll(contactSpec,
pageSpecification);

return page.getContent();
}

Querydsl
Since the ContactRepository interface extends the
QueryDslPredicateExecutor<T> interface, we got access to the Page<Contact>
findAll(Predicate predicate, Pageable page) method that we can use
to paginate query results. In order to add pagination support to our search
function, we have to make some changes to the existing search() method of the
RepositoryContactService class. The new implementation of this method is
described in the following steps:

1. We get a reference to the used Predicate .

2. We get the used PageRequest object.