SpringData JPARepository流MySql/MsSql

Question

我正在使用SpringData JPARepository从MySql和MsSql databases.When读取数据，我尝试以列表的形式获取查询结果。它工作得非常好。

 List<Employee> findByEmployeeId(String employeeId);

但当我尝试以流的形式获取

 Stream<Employee> findByEmployeeId(String employeeId);

我得到了NPE。但这会间歇性地发生。

java.lang.NullPointerException: null
    at com.mysql.jdbc.ResultSetImpl.findColumn(ResultSetImpl.java:1044) ~[mysql-connector-java-5.1.38.jar!/:5.1.38]
    at com.mysql.jdbc.ResultSetImpl.getInt(ResultSetImpl.java:2580) ~[mysql-connector-java-5.1.38.jar!/:5.1.38]
    at com.zaxxer.hikari.pool.HikariProxyResultSet.getInt(HikariProxyResultSet.java) ~[HikariCP-2.4.3.jar!/:na]
    at org.hibernate.type.descriptor.sql.IntegerTypeDescriptor$2.doExtract(IntegerTypeDescriptor.java:73) ~[hibernate-core-4.3.11.Final.jar!/:4.3.11.Final]
    at org.hibernate.type.descriptor.sql.BasicExtractor.extract(BasicExtractor.java:64) ~[hibernate-core-4.3.11.Final.jar!/:4.3.11.Final]
    at org.hibernate.type.AbstractStandardBasicType.nullSafeGet(AbstractStandardBasicType.java:267) ~[hibernate-core-4.3.11.Final.jar!/:4.3.11.Final]
    at org.hibernate.type.AbstractStandardBasicType.nullSafeGet(AbstractStandardBasicType.java:263) ~[hibernate-core-4.3.11.Final.jar!/:4.3.11.Final]
    at org.hibernate.type.AbstractStandardBasicType.nullSafeGet(AbstractStandardBasicType.java:253) ~[hibernate-core-4.3.11.Final.jar!/:4.3.11.Final]
    at org.hibernate.type.AbstractStandardBasicType.hydrate(AbstractStandardBasicType.java:338) ~[hibernate-core-4.3.11.Final.jar!/:4.3.11.Final]
    at org.hibernate.persister.entity.AbstractEntityPersister.hydrate(AbstractEntityPersister.java:2969) ~[hibernate-core-4.3.11.Final.jar!/:4.3.11.Final]
    at org.hibernate.loader.Loader.loadFromResultSet(Loader.java:1696) ~[hibernate-core-4.3.11.Final.jar!/:4.3.11.Final]
    at org.hibernate.loader.Loader.instanceNotYetLoaded(Loader.java:1628) ~[hibernate-core-4.3.11.Final.jar!/:4.3.11.Final]
    at org.hibernate.loader.Loader.getRow(Loader.java:1515) ~[hibernate-core-4.3.11.Final.jar!/:4.3.11.Final]
    at org.hibernate.loader.Loader.getRowFromResultSet(Loader.java:726) ~[hibernate-core-4.3.11.Final.jar!/:4.3.11.Final]
    at org.hibernate.loader.Loader.getRowFromResultSet(Loader.java:696) ~[hibernate-core-4.3.11.Final.jar!/:4.3.11.Final]
    at org.hibernate.loader.Loader.loadSingleRow(Loader.java:392) ~[hibernate-core-4.3.11.Final.jar!/:4.3.11.Final]
    at org.hibernate.internal.ScrollableResultsImpl.prepareCurrentRow(ScrollableResultsImpl.java:237) ~[hibernate-core-4.3.11.Final.jar!/:4.3.11.Final]
    at org.hibernate.internal.ScrollableResultsImpl.next(ScrollableResultsImpl.java:121) ~[hibernate-core-4.3.11.Final.jar!/:4.3.11.Final]
    at org.springframework.data.jpa.provider.PersistenceProvider$HibernateScrollableResultsIterator.hasNext(PersistenceProvider.java:396) ~[spring-data-jpa-1.9.2.RELEASE.jar!/:na]
    at java.util.Iterator.forEachRemaining(Iterator.java:115) ~[na:1.8.0_66]
    at java.util.Spliterators$IteratorSpliterator.forEachRemaining(Spliterators.java:1801) ~[na:1.8.0_66]
    at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:481) ~[na:1.8.0_66]
    at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471) ~[na:1.8.0_66]
    at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:708) ~[na:1.8.0_66]
    at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234) ~[na:1.8.0_66]
    at java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:499) ~[na:1.8.0_66]

但是使用MongoRepository我从来没有遇到过问题，即使是巨大的结果。

如果我遗漏了什么，请告诉我。

谢谢

Answer 1

您是否尝试过在存储库方法的查询中添加@Query注释？我见过并使用过的所有以Stream作为返回类型的查询都使用了它的注释。

下面是你的例子：

@Query(value = "select e from Employee e where e.employeeId = :employeeId)
Stream<Employee> findByEmployeeId(String employeeId)