Forked from tcollins/-Spring-JPA-Dynamic-Query-With-Limit
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September 21, 2022 09:31
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Spring Data JPA - Limit results when using Specifications without an unnecessary count query being executed
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If you use the findAll(Specification, Pageable) method, a count query is first executed and then the | |
data query is executed if the count returns a value greater than the offset. | |
For what I was doing I did not need pageable, but simply wanted to limit my results. This is easy | |
to do with static named queries and methodNameMagicGoodness queries, but from my research (googling | |
for a few hours) I couldn't find a way to do it with dynamic criteria queries using Specifications. | |
During my search I found two things that helped me to figure out how to just do it myself. | |
1.) A stackoverflow question. | |
How to disable count when Specification and Pageable are used together? | |
http://stackoverflow.com/questions/26738199/how-to-disable-count-when-specification-and-pageable-are-used-together | |
(where I will add a link to this gist) | |
2.) Spring documentation - Adding custom behavior to all repositories | |
http://docs.spring.io/spring-data/data-jpa/docs/current/reference/html/#repositories.custom-behaviour-for-all-repositories | |
I followed the Spring documentation pretty closely and got this all working pretty quickly without | |
any real problems. |
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@NoRepositoryBean | |
public interface BaseRepository<T, ID extends Serializable> extends JpaRepository<T, ID> { | |
List<T> findAll(Specification<T> spec, int offset, int maxResults, Sort sort); | |
List<T> findAll(Specification<T> spec, int offset, int maxResults); | |
} |
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public class BaseRepositoryFactoryBean<R extends JpaRepository<T, I>, T, I extends Serializable> extends JpaRepositoryFactoryBean<R, T, I> { | |
@SuppressWarnings("rawtypes") | |
@Override | |
protected RepositoryFactorySupport createRepositoryFactory(EntityManager entityManager) { | |
return new BaseRepositoryFactory(entityManager); | |
} | |
private static class BaseRepositoryFactory<T, I extends Serializable> extends JpaRepositoryFactory { | |
private final EntityManager em; | |
public BaseRepositoryFactory(EntityManager em) { | |
super(em); | |
this.em = em; | |
} | |
@SuppressWarnings({ "unchecked", "rawtypes", "hiding" }) | |
protected <T, ID extends Serializable> SimpleJpaRepository<?, ?> getTargetRepository(RepositoryMetadata metadata, EntityManager entityManager) { | |
SimpleJpaRepository<?, ?> repo = new BaseRepositoryImpl(metadata.getDomainType(), entityManager); | |
return repo; | |
} | |
protected Class<?> getRepositoryBaseClass(RepositoryMetadata metadata) { | |
return BaseRepositoryImpl.class; | |
} | |
} | |
} |
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public class BaseRepositoryImpl<T, ID extends Serializable> extends SimpleJpaRepository<T, ID> implements BaseRepository<T, ID> { | |
private final EntityManager entityManager; | |
public BaseRepositoryImpl(Class<T> domainClass, EntityManager entityManager) { | |
super(domainClass, entityManager); | |
this.entityManager = entityManager; | |
} | |
public List<T> findAll(Specification<T> spec, int offset, int maxResults) { | |
return findAll(spec, offset, maxResults, null); | |
} | |
public List<T> findAll(Specification<T> spec, int offset, int maxResults, Sort sort) { | |
TypedQuery<T> query = getQuery(spec, sort); | |
if (offset < 0) { | |
throw new IllegalArgumentException("Offset must not be less than zero!"); | |
} | |
if (maxResults < 1) { | |
throw new IllegalArgumentException("Max results must not be less than one!"); | |
} | |
query.setFirstResult(offset); | |
query.setMaxResults(maxResults); | |
return query.getResultList(); | |
} | |
} |
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@SpringBootApplication | |
@EnableJpaRepositories(repositoryFactoryBeanClass = BaseRepositoryFactoryBean.class) | |
public class MySpringBootApplication { | |
public static void main(String[] args) { | |
SpringApplication app = new SpringApplication(MySpringBootApplication.class); | |
app.run(args); | |
} | |
} |
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// This is just to show an example of a repo | |
public interface UserRepository extends BaseRepository<User, Long>, JpaSpecificationExecutor<User> { | |
} |
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