在查詢DSL + Spring Data JPA中進行分組，並拋出NoSuchElementException

Question

我正在嘗試使用Spring Data JPA和Query DSL按組執行查詢。

但是，我得到以下異常：

org.springframework.beans.factory.UnsatisfiedDependencyException: 
Error creating bean with name 'japanWHTDaoImpl': 
   Unsatisfied dependency expressed through field 'wht21940000DataRepo'; 
       nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'japanWHT21940000DataRepository': 
    Invocation of init method failed; nested exception is java.util.NoSuchElementException

我試圖編寫自定義存儲庫實現，並在下面的接口和impl類中給出以下信息：

自定義界面：

public interface JapanWHT21940000DataRepositoryCustom {
        List<WHT21940000Royalties> findLocalCcyAmtsByRemarks();
}

自定義Impl類：

@Repository
@Transactional
public class JapanWHT21940000DataRepositoryCustomImpl extends QueryDslRepositorySupport implements JapanWHT21940000DataRepositoryCustom {

    public JapanWHT21940000DataRepositoryCustomImpl(Class<?> domainClass) {
    super(domainClass);
    // TODO Auto-generated constructor stub
    }

    @PersistenceContext
    private EntityManager entityManager;

    @Override
    public List<WHT21940000Royalties> findLocalCcyAmtsByRemarks() {
    QWHT21940000Data wht21940000Data = QWHT21940000Data.wHT21940000Data;
    JPAQuery<WHT21940000Royalties> query = new JPAQuery<WHT21940000Royalties>(entityManager);
    query.from(wht21940000Data).groupBy(wht21940000Data.remarks).select(wht21940000Data.remarks, wht21940000Data.localCcyAmt.sum());

    return null;
    }

}

Spring數據JPA接口：

public interface JapanWHT21940000DataRepository
    extends JpaRepository<WHT21940000Data, Long>, 
        QueryDslPredicateExecutor<WHT21940000Data>, 
        JapanWHT21940000DataRepositoryCustom {

}

在DAO類中：

@Repository
@Transactional("japanWhtTransactionManager")
public class JapanWHTDaoImpl implements JapanWHTDao {
    @Autowired
    JapanWHT21940000DataRepository wht21940000DataRepo;
    // more code to follow...

編輯：還是有比我正在嘗試的方法更簡單更好的方法來按Spring數據JPA +查詢DSL進行分組查詢？

Answer 1

我認為真正的問題是從JpaRepositories執行定制的querydsl查詢，盡管我建議使用定制的擴展基礎存儲庫類，如下所示。

首先，擴展基礎存儲庫類。

@NoRepositoryBean
public interface ExtendedQueryDslJpaRepository<T, ID extends Serializable> extends JpaRepository<T, ID>, QueryDslPredicateExecutor<T> {

    <T1> Page<T1> findAll(JPQLQuery jpqlQuery, Pageable pageable);
}

和相關的實現。

public class ExtendedQueryDslJpaRepositoryImpl<T, ID extends Serializable>
    extends QueryDslJpaRepository<T, ID> implements ExtendedQueryDslJpaRepository<T, ID> {

    private static final EntityPathResolver DEFAULT_ENTITY_PATH_RESOLVER = SimpleEntityPathResolver.INSTANCE;

    private final EntityPath<T> path;
    private final PathBuilder<T> builder;
    private final Querydsl querydsl;

    private EntityManager entityManager;

    public ExtendedQueryDslJpaRepositoryImpl(JpaEntityInformation<T, ID> entityInformation, EntityManager entityManager) {
        this(entityInformation, entityManager, DEFAULT_ENTITY_PATH_RESOLVER);
    }

    public ExtendedQueryDslJpaRepositoryImpl(JpaEntityInformation<T, ID> entityInformation, EntityManager entityManager, EntityPathResolver
        resolver) {

        super(entityInformation, entityManager);
        this.path = resolver.createPath(entityInformation.getJavaType());
        this.builder = new PathBuilder(this.path.getType(), this.path.getMetadata());
        this.querydsl = new Querydsl(entityManager, this.builder);
        this.entityManager = entityManager;
    }

    @Override
    public <T1> Page<T1> findAll(JPQLQuery jpqlQuery, Pageable pageable) {

        final JPQLQuery<?> countQuery = jpqlQuery;

        JPQLQuery<T1> query = querydsl.applyPagination(pageable, jpqlQuery);

        return PageableExecutionUtils.getPage(query.fetch(), pageable, countQuery::fetchCount);
    }
}

上面的類可以放在配置包中。

然后，我們將ExtendedQueryDslJpaRepositoryImpl定義為JpaRepository類應從其ExtendedQueryDslJpaRepositoryImpl默認類，如下所示：

@Configuration
@EnableJpaRepositories(basePackageClasses = Application.class, repositoryBaseClass = ExtendedQueryDslJpaRepositoryImpl.class)
public class JpaConfig {

    @PersistenceContext
    private EntityManager entityManager;

    @Bean
    public JPAQueryFactory jpaQueryFactory() {
        return new JPAQueryFactory(entityManager);
    }
}

下一步是為應用程序的Entity定義存儲庫，例如。 CustomEntity 。

public interface CustomRepository extends ExtendedQueryDslJpaRepository<CustomEntity, Long>, CustomRepositorySupport {
}

接下來，我們為自定義方法定義定義接口CustomRepositorySupport 。

public interface CustomRepositorySupport {

    JPQLQuery<CustomListDto> createCustomIndexQuery();
}

最后是自定義存儲庫實現。

@Repository
public class CustomRepositoryImpl implements CustomRepositorySupport {

    private JPAQueryFactory queryFactory;

    @Autowired
    public CustomRepositoryImpl(JPAQueryFactory queryFactory) {
        this.queryFactory = queryFactory;
    }

    @Override
    public JPQLQuery<CustomListDto> createCustomIndexQuery() {

        QCustomEntity qCustomEntity = QCustomEntity.customEntity;

        BooleanBuilder predicate = new BooleanBuilder();

        // Create predicate as desired
        // predicate.and(...);

        // Create projection of fields
        /* FactoryExpression<CustomListDto> factoryExpression = Projections.bean(CustomListDto.class,
            qCustomEntity.fieldA,
            qCustomEntity.fieldB,
            qCustomEntity.fieldC,
            qCustomEntity.fieldD,
            qCustomEntity.fieldE,
            qCustomEntity.fieldF); */

        return queryFactory.from(qCustomEntity).select(factoryExpression).where(predicate);
    }
}

最后一步是從Service類實際調用該方法，如下所示。

public interface CustomFinder {

    Page<CustomListDto> findIndex(Pageable pageable);
}

--

@Service
public class CustomFinderImpl implements CustomFinder {

    private CustomRepository customRepository;

    @Autowired
    public CustomFinderImpl(CustomRepository customRepository) {
        this.customRepository = customRepository;
    }

    @Override
    public Page<CustomListDto> findIndex(Pageable pageable) {

        JPQLQuery<CustomListDto> query = customRepository.createCustomIndexQuery();

        return customRepository.findAll(query, pageable);
    }
}

與我們實現public <T1> List<T1> findAll(JPQLQuery query, FactoryExpression<T1> factoryExpression) ，我們可以簡單地實現所需的所需方法，如public <T1> List<T1> findAll(JPQLQuery query, FactoryExpression<T1> factoryExpression) <T1> List<T1> findList(JPQLQuery query, FactoryExpression<T1> factoryExpression)等

這樣，我們為所有存儲庫添加了功能，以便利用所有類型的querydsl查詢，而不僅是group by或projections 。

它看起來似乎有些復雜，但是如果您選擇實現它，並查看它如何工作，則您會堅持下去。 它已在實際應用程序中成功使用，可以訪問投影查詢（無需在不需要它們的情況下加載完整實體），分頁查詢，存在子查詢等。

最后，使用一種中央基礎存儲庫類是一種僅可編寫一次的可重用代碼。

希望能有所幫助。