hibernate not null属性引用空值或瞬时值：

这个问题随机出现。这个程序已经运行了一个多月，但今天它崩溃了。添加新订单时，用户可以从下拉列表中选择公司。然后他可以将新订单保存到数据库中。即使是现在，当用户重新加载应用程序时，大多数情况下它都能正常工作。错误代码如下所示：

javax.persistence.PersistenceException:org.hibernate.PropertyValueException:notnull属性引用null或瞬态值：mapped.Order.company（odwzorowania.Zlecenie.firma）

使用Hibernate、JSF2.1、MySql 5.5、javax.persistence.*

这是代码（名字是从波兰语翻译过来的）

订单实体

    import javax.persistence.* //fixed in real code

    @Entity
    @Table(name = "order")


    public class Order implements Serializable {
    private static final long serialVersionUID = 1L;

    private Integer idOrder;
    private Company company;
    [...]

    @JoinColumn(name = "company_idCompany", referencedColumnName = "idCompany")
    @ManyToOne(optional = false, fetch = FetchType.LAZY)
    public Company getCompany() {
        return company;
    }

    public void setCompany(Company company) {
        this.company = company;
    }
    [...]

公司实体

import javax.persistence.*

@Entity
@Table(name = "company")

public class Company implements Serializable {

private static final long serialVersionUID = 1L;

private Integer idCompany;       
private List<Order> orderList;
[...]

@OneToMany(mappedBy = "company", fetch = FetchType.LAZY)
public List<Order> getOrderList() {
    return orderList;
}

public void setOrderList(List<Order>orderList) {
    this.orderList = orderList;
}
[...]

导入javax.persistence* @实体 @表（name=“公司”） 公共类公司实现可序列化{ 私有静态最终长serialVersionUID=1L； 私营公司； 私有列表订单列表； [...] @OneToMany（mappedBy=“company”，fetch=FetchType.LAZY） 公共列表getOrderList（）{ 返回订单列表； } 公共无效setOrderList（ListorderList）{ this.orderList=订单列表； } [...] 堆栈跟踪（mapped.Order.company与从波兰语翻译过来的odwzorowania.Zlecenie.firma相同）

2012 xx xx xx:xx:xx com.sun.faces.application.ApplicationImpl newThing
严重：无法加载类别：
javax.persistence.PersistenceException:org.hibernate.PropertyValueException:notnull属性引用空值或瞬时值：odwzorowania.Zlecenie.firma
位于org.hibernate.ejb.AbstractEntityManagerImpl.throwPersistenceException（AbstractEntityManagerImpl.java:637）
位于org.hibernate.ejb.QueryImpl.getResultList（QueryImpl.java:74）
位于controllery.FirmaController.get（FirmaController.java:84）
在validary.FirmyValidator（FirmyValidator.java:32）
位于sun.reflect.generatedconstructor或accessor154.newInstance（未知源）
在sun.reflect.DelegatingConstructorAccessorImpl.newInstance（DelegatingConstructorAccessorImpl.java:45）
位于java.lang.reflect.Constructor.newInstance（Constructor.java:532）
位于java.lang.Class.newInstance0（Class.java:372）
位于java.lang.Class.newInstance（Class.java:325）
位于com.sun.faces.application.ApplicationImpl.newThing（ApplicationImpl.java:1699）
位于com.sun.faces.application.ApplicationImpl.createValidator（ApplicationImpl.java:1557）
位于com.sun.faces.facelets.tag.jsf.ValidatorTagHandlerDelegateImpl.createValidator（ValidatorTagHandlerDelegateImpl.java:238）
位于com.sun.faces.facelets.tag.jsf.ValidatorTagHandlerDelegateImpl.applyAttachedObject（ValidatorTagHandlerDelegateImpl.java:132）
位于com.sun.faces.facelets.tag.jsf.ValidatorTagHandlerDelegateImpl.applyNested（ValidatorTagHandlerDelegateImpl.java:205）
位于com.sun.faces.facelets.tag.jsf.ValidatorTagHandlerDelegateImpl.apply（ValidatorTagHandlerDelegateImpl.java:87）
位于javax.faces.view.facelets.DelegatingMetaTagHandler.apply（DelegatingMetaTagHandler.java:120）
在javax.faces.view.facelets.CompositeFaceletHandler.apply（CompositeFaceletHandler.java:98）
位于javax.faces.view.facelets.DelegatingMetaTagHandler.applyNextHandler（DelegatingMetaTagHandler.java:137）
位于com.sun.faces.facelets.tag.jsf.ComponentTagHandlerDelegateImpl.apply（ComponentTagHandlerDelegateImpl.java:188）
位于javax.faces.view.facelets.DelegatingMetaTagHandler.apply（DelegatingMetaTagHandler.java:120）
在javax.faces.view.facelets.CompositeFaceletHandler.apply（CompositeFaceletHandler.java:98）
位于javax.faces.view.facelets.DelegatingMetaTagHandler.applyNextHandler（DelegatingMetaTagHandler.java:137）
位于com.sun.faces.facelets.tag.jsf.ComponentTagHandlerDelegateImpl.apply（ComponentTagHandlerDelegateImpl.java:188）
位于javax.faces.view.facelets.DelegatingMetaTagHandler.apply（DelegatingMetaTagHandler.java:120）
在javax.faces.view.facelets.CompositeFaceletHandler.apply（CompositeFaceletHandler.java:98）
位于javax.faces.view.facelets.DelegatingMetaTagHandler.applyNextHandler（DelegatingMetaTagHandler.java:137）
位于com.sun.faces.facelets.tag.jsf.ComponentTagHandlerDelegateImpl.apply（ComponentTagHandlerDelegateImpl.java:188）
位于javax.faces.view.facelets.DelegatingMetaTagHandler.apply（DelegatingMetaTagHandler.java:120）
在javax.faces.view.facelets.CompositeFaceletHandler.apply（CompositeFaceletHandler.java:98）
位于com.sun.faces.facelets.compiler.NamespaceHandler.apply（NamespaceHandler.java:93）
在javax.faces.view.facelets.CompositeFaceletHandler.apply（CompositeFaceletHandler.java:98）
位于com.sun.faces.facelets.compiler.EncodingHandler.apply（EncodingHandler.java:86）
在com.sun.faces.facelets.impl.DefaultFacelet.apply（DefaultFacelet.java:152）上
位于com.sun.faces.application.view.FaceletViewHandlingStrategy.buildView（FaceletViewHandlingStrategy.java:769）
位于com.sun.faces.application.view.StateManagementStrategyImpl.restoreView（StateManagementStrategyImpl.java:232）
位于com.sun.faces.application.StateManagerImpl.restoreView（StateManagerImpl.java:188）
在com.sun.faces.application.view.ViewHandlingStrategy.restoreView（ViewHandlingStrategy.java:123）上
在com.sun.faces.application.view.FaceletViewHandlingStrategy.restoreView（FaceletViewHandlingStrategy.java:452）
在com.sun.faces.application.view.MultiViewHandler.restoreView（MultiViewHandler.java:148）上
位于com.sun.faces.lifecycle.RestoreViewPhase.execute（RestoreViewPhase.java:192）
位于com.sun.faces.lifecycle.Phase.doPhase（Phase.java:101）
位于com.sun.faces.lifecycle.RestoreViewPhase.doPhase（RestoreViewPhase.java:116）
在com.sun.faces.lifecycle.LifecycleImpl.execute（LifecycleImpl.java:118）上
位于javax.faces.webapp.FacesServlet.service（FacesServlet.java:409）
位于org.apache.catalina.core.ApplicationFilterChain.internalDoFilter（ApplicationFilterChain.java:305）
位于org.apache.catalina.core.ApplicationFilterChain.doFilter（ApplicationFilterChain.java:210）
位于org.apache.catalina.core.StandardWrapperValve.invoke（StandardWrapperValve.java:225）
import javax.persistence.*

@Entity
@Table(name = "company")

public class Company implements Serializable {

private static final long serialVersionUID = 1L;

private Integer idCompany;       
private List<Order> orderList;
[...]

@OneToMany(mappedBy = "company", fetch = FetchType.LAZY)
public List<Order> getOrderList() {
    return orderList;
}

public void setOrderList(List<Order>orderList) {
    this.orderList = orderList;
}
[...]

2012-xx-xx xx:xx:xx com.sun.faces.application.ApplicationImpl newThing
SEVERE: Unable to load class: 
javax.persistence.PersistenceException: org.hibernate.PropertyValueException: not-null property references a null or transient value: odwzorowania.Zlecenie.firma
    at org.hibernate.ejb.AbstractEntityManagerImpl.throwPersistenceException(AbstractEntityManagerImpl.java:637)
    at org.hibernate.ejb.QueryImpl.getResultList(QueryImpl.java:74)
    at controllery.FirmaController.get(FirmaController.java:84)
    at validatory.FirmyValidator.<init>(FirmyValidator.java:32)
    at sun.reflect.GeneratedConstructorAccessor154.newInstance(Unknown Source)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:532)
    at java.lang.Class.newInstance0(Class.java:372)
    at java.lang.Class.newInstance(Class.java:325)
    at com.sun.faces.application.ApplicationImpl.newThing(ApplicationImpl.java:1699)
    at com.sun.faces.application.ApplicationImpl.createValidator(ApplicationImpl.java:1557)
    at com.sun.faces.facelets.tag.jsf.ValidatorTagHandlerDelegateImpl.createValidator(ValidatorTagHandlerDelegateImpl.java:238)
    at com.sun.faces.facelets.tag.jsf.ValidatorTagHandlerDelegateImpl.applyAttachedObject(ValidatorTagHandlerDelegateImpl.java:132)
    at com.sun.faces.facelets.tag.jsf.ValidatorTagHandlerDelegateImpl.applyNested(ValidatorTagHandlerDelegateImpl.java:205)
    at com.sun.faces.facelets.tag.jsf.ValidatorTagHandlerDelegateImpl.apply(ValidatorTagHandlerDelegateImpl.java:87)
    at javax.faces.view.facelets.DelegatingMetaTagHandler.apply(DelegatingMetaTagHandler.java:120)
    at javax.faces.view.facelets.CompositeFaceletHandler.apply(CompositeFaceletHandler.java:98)
    at javax.faces.view.facelets.DelegatingMetaTagHandler.applyNextHandler(DelegatingMetaTagHandler.java:137)
    at com.sun.faces.facelets.tag.jsf.ComponentTagHandlerDelegateImpl.apply(ComponentTagHandlerDelegateImpl.java:188)
    at javax.faces.view.facelets.DelegatingMetaTagHandler.apply(DelegatingMetaTagHandler.java:120)
    at javax.faces.view.facelets.CompositeFaceletHandler.apply(CompositeFaceletHandler.java:98)
    at javax.faces.view.facelets.DelegatingMetaTagHandler.applyNextHandler(DelegatingMetaTagHandler.java:137)
    at com.sun.faces.facelets.tag.jsf.ComponentTagHandlerDelegateImpl.apply(ComponentTagHandlerDelegateImpl.java:188)
    at javax.faces.view.facelets.DelegatingMetaTagHandler.apply(DelegatingMetaTagHandler.java:120)
    at javax.faces.view.facelets.CompositeFaceletHandler.apply(CompositeFaceletHandler.java:98)
    at javax.faces.view.facelets.DelegatingMetaTagHandler.applyNextHandler(DelegatingMetaTagHandler.java:137)
    at com.sun.faces.facelets.tag.jsf.ComponentTagHandlerDelegateImpl.apply(ComponentTagHandlerDelegateImpl.java:188)
    at javax.faces.view.facelets.DelegatingMetaTagHandler.apply(DelegatingMetaTagHandler.java:120)
    at javax.faces.view.facelets.CompositeFaceletHandler.apply(CompositeFaceletHandler.java:98)
    at com.sun.faces.facelets.compiler.NamespaceHandler.apply(NamespaceHandler.java:93)
    at javax.faces.view.facelets.CompositeFaceletHandler.apply(CompositeFaceletHandler.java:98)
    at com.sun.faces.facelets.compiler.EncodingHandler.apply(EncodingHandler.java:86)
    at com.sun.faces.facelets.impl.DefaultFacelet.apply(DefaultFacelet.java:152)
    at com.sun.faces.application.view.FaceletViewHandlingStrategy.buildView(FaceletViewHandlingStrategy.java:769)
    at com.sun.faces.application.view.StateManagementStrategyImpl.restoreView(StateManagementStrategyImpl.java:232)
    at com.sun.faces.application.StateManagerImpl.restoreView(StateManagerImpl.java:188)
    at com.sun.faces.application.view.ViewHandlingStrategy.restoreView(ViewHandlingStrategy.java:123)
    at com.sun.faces.application.view.FaceletViewHandlingStrategy.restoreView(FaceletViewHandlingStrategy.java:452)
    at com.sun.faces.application.view.MultiViewHandler.restoreView(MultiViewHandler.java:148)
    at com.sun.faces.lifecycle.RestoreViewPhase.execute(RestoreViewPhase.java:192)
    at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
    at com.sun.faces.lifecycle.RestoreViewPhase.doPhase(RestoreViewPhase.java:116)
    at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118)
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:409)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:225)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:169)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:927)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:999)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:565)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:309)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
    at java.lang.Thread.run(Thread.java:636)
Caused by: org.hibernate.PropertyValueException: not-null property references a null or transient value: odwzorowania.Zlecenie.firma
    at org.hibernate.engine.Nullability.checkNullability(Nullability.java:72)
    at org.hibernate.event.def.DefaultFlushEntityEventListener.scheduleUpdate(DefaultFlushEntityEventListener.java:270)
    at org.hibernate.event.def.DefaultFlushEntityEventListener.onFlushEntity(DefaultFlushEntityEventListener.java:128)
    at org.hibernate.event.def.AbstractFlushingEventListener.flushEntities(AbstractFlushingEventListener.java:196)
    at org.hibernate.event.def.AbstractFlushingEventListener.flushEverythingToExecutions(AbstractFlushingEventListener.java:76)
    at org.hibernate.event.def.DefaultAutoFlushEventListener.onAutoFlush(DefaultAutoFlushEventListener.java:35)
    at org.hibernate.impl.SessionImpl.autoFlushIfRequired(SessionImpl.java:969)
    at org.hibernate.impl.SessionImpl.list(SessionImpl.java:1114)
    at org.hibernate.impl.QueryImpl.list(QueryImpl.java:79)
    at org.hibernate.ejb.QueryImpl.getResultList(QueryImpl.java:65)
    ... 58 more

@ManyToOne(**optional = false**, fetch = FetchType.LAZY)