相关疑难解决方法(0)

我需要从DB只带一个结果.我怎么能用JPA做到这一点？

Select top 1 * from table

我试过了

"从表格中选择t"

query.setMaxResults(1);

query.getSingleResult();

但没有奏效.还有其他想法吗？

一个简单的问题,因为我确信这是愚蠢的.我有以下查询,我可以在NetBeans sql命令窗口中执行:

SELECT TOP 25 * FROM ARCUST_BIG  WHERE arcustno<='300000' ORDER BY arcustno DESC

我的目标是将它放在我的ArcustRepository类中:

公共接口ArcustRepository扩展了JpaRepository {

Arcust findByPrimaryKey(String id);

@Query("SELECT COUNT(a) FROM Arcust a")
Long countAll();

@Query("SELECT TOP 25 a FROM Arcust a WHERE a.arcustno<='?1' ORDER BY a.arcustno DESC")
List<Arcust> findByTop(String arcustno);
}

但是,findBytop查询似乎不起作用,当我用tomcat7启动我的服务时返回:

2013-08-15 08:15:20 ERROR ContextLoader:319 - Context initialization failed
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'arcustService': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private com.waudware.pics.repository.ArcustRepository com.waudware.pics.service.ArcustService.arcustRepository; nested exception is org.springframework.beans.factory.BeanCreationException: …

有没有办法让CrudRepository接口对具有多行的表进行排序并简单地返回第一行,例如按时间戳排序以仅返回最新的行？

public interface ImportReceiptRepository extends CrudRepository<ImportReceipt, Long>
{
    ImportReceipt getOneByImportTypeOrderByTimestampDesc(String importType);
    ImportReceipt findOneByImportTypeOrderByTimestampDesc(String importType);
}

findOneBy ...和getOneBy ... throw:

org.springframework.dao.IncorrectResultSizeDataAccessException: result returns more than one elements; nested exception is javax.persistence.NonUniqueResultException: result returns more than one elements
at org.springframework.orm.jpa.EntityManagerFactoryUtils.convertJpaAccessExceptionIfPossible(EntityManagerFactoryUtils.java:395)
at org.springframework.orm.jpa.vendor.HibernateJpaDialect.translateExceptionIfPossible(HibernateJpaDialect.java:216)
at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.translateExceptionIfPossible(AbstractEntityManagerFactoryBean.java:417)
at org.springframework.dao.support.ChainedPersistenceExceptionTranslator.translateExceptionIfPossible(ChainedPersistenceExceptionTranslator.java:59)
at org.springframework.dao.support.DataAccessUtils.translateIfNecessary(DataAccessUtils.java:213)
at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:147)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
at org.springframework.data.jpa.repository.support.LockModeRepositoryPostProcessor$LockModePopulatingMethodIntercceptor.invoke(LockModeRepositoryPostProcessor.java:105)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:207)
at com.sun.proxy.$Proxy109.findOneByImportTypeOrderByTimestampDesc(Unknown Source)
at edu.ucdavis.dss.dw.services.DefaultImportReceiptService.getLatestOneByImportType(DefaultImportReceiptService.java:26)
...

或者,换句话说,CrudRepository相当于:

SELECT * FROM ImportReceipts ORDER BY timestamp DESC LIMIT 0,1;