我正在使用hibernate。我有两张桌子：工作和公司。
Company.hbm.xml是：
<class name="com.jobs.admin.data.Company" table="S_COMPANY">
<id name="companyKid" column="COMPANY_KID" type="integer">
<generator class="sequence">
<param name="sequence">company_sequence</param>
</generator>
</id>
<property name="companyName" column="COMPANY_NAME" length="200" type="string" unique="true"/>
<property name="companyDesc" column="COMPANY_DESC" type="string" length="1000" unique="true" />
<property name="companySName" column="COMPANY_SNAME" type="string" length="100"/>
<property name="companyMail" column="COMPANY_MAIL" type="string" length="200"/>
<property name="companyPhone" column="COMPANY_PHONE" type="string" length="200"/>
</class>
我的Job.hbm.xml是：
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="com.jobs.admin.data.Job" table="S_JOBS">
<id name="jobKid" column="JOB_KID" type="integer">
<generator class="sequence">
<param name="sequence">job_sequence</param>
</generator>
</id>
<property name="jobTitle" column="JOB_TITLE" type="string"/>
<property name="jobDesc" column="JOB_DESC" type="string"></property>
<!-- <property name="jobCompany" column="JOB_COMPANY" type="integer"></property>-->
<property name="jobCity" column="JOB_CITY" type="integer"></property>
<property name="jobExp" column="JOB_EXP" type="integer"></property>
<property name="jobCat" column="JOB_CAT" type="integer"></property>
<property name="jobStartDate" column="JOB_STARTDATE" type="string"></property>
<property name="jobEndDate" column="JOB_ENDDATE" type="string"></property>
<many-to-one name="jobCompany" class="com.jobs.admin.data.Company" column="JOB_COMPANY" property-ref="companyKid" ></many-to-one>
</class>
</hibernate-mapping>
这是我加入这些表的方法代码
List<com.jobs.admin.data.JobCat> jobCat= null;
db_session= HibernateSessionFactory.getSessionFactory().openSession();
transaction=null;
try{
transaction = db_session.beginTransaction();
jobCat = db_session.createQuery("from Job as job inner join job.jobCompany as company").list();
transaction.commit();
}
catch (HibernateException e) {
transaction.rollback();
e.printStackTrace();
} finally {
db_session.close();
}
return jobCat;
当我跑步时，它给了我以下例外：
java.lang.NullPointerException
at org.hibernate.persister.entity.AbstractEntityPersister.loadByUniqueKey(AbstractEntityPersister.java:1662)
at org.hibernate.type.EntityType.loadByUniqueKey(EntityType.java:641)
at org.hibernate.type.EntityType.resolve(EntityType.java:415)
at org.hibernate.engine.TwoPhaseLoad.initializeEntity(TwoPhaseLoad.java:139)
at org.hibernate.loader.Loader.initializeEntitiesAndCollections(Loader.java:877)
at org.hibernate.loader.Loader.doQuery(Loader.java:752)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:259)
at org.hibernate.loader.Loader.doList(Loader.java:2232)
at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2129)
at org.hibernate.loader.Loader.list(Loader.java:2124)
at org.hibernate.loader.hql.QueryLoader.list(QueryLoader.java:401)
at org.hibernate.hql.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:363)
at org.hibernate.engine.query.HQLQueryPlan.performList(HQLQueryPlan.java:196)
at org.hibernate.impl.SessionImpl.list(SessionImpl.java:1149)
at org.hibernate.impl.QueryImpl.list(QueryImpl.java:102)
at com.jobs.admin.service.JobImpl.getJobs(JobImpl.java:91)
at com.jobs.admin.controller.JobController.showViewJobs(JobController.java:64)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.doInvokeMethod(HandlerMethodInvoker.java:710)
at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:167)
at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:414)
at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:402)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:771)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:716)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:647)
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:552)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:690)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:230)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:104)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:261)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:581)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
at java.lang.Thread.run(Thread.java:619)
请建议我，我的错误是什么？