Hibernate JPA 2.1按提示查找,如果@NamedEntityGraph中存在多个@NamedSubgraph,则返回冗余结果
在我的项目中,我将**JPA 2.1**与**Hibernate 5.0.2.final**结合使用。 问题是,当我加载类型为{@EventTO}的实例时,如果该实例一次没有与会者和assignedResources或其中一个集合,它将正确加载;但是,如果同时具有这两个集合,则实体图获取的结果将携带冗余数据。例如,如果有3个与会者和2个assignedResources,作为提示,它将返回4个与会者和3个assignedResources。我对这种行为感到困惑。我不知道为什么???。可能与hibernate查询有关,但我不确定。Hibernate JPA 2.1按提示查找,如果@NamedEntityGraph中存在多个@NamedSubgraph,则返回冗余结果,hibernate,jpa,repeat,subgraph,Hibernate,Jpa,Repeat,Subgraph,在我的项目中,我将**JPA 2.1**与**Hibernate 5.0.2.final**结合使用。 问题是,当我加载类型为{@EventTO}的实例时,如果该实例一次没有与会者和assignedResources或其中一个集合,它将正确加载;但是,如果同时具有这两个集合,则实体图获取的结果将携带冗余数据。例如,如果有3个与会者和2个assignedResources,作为提示,它将返回4个与会者和3个assignedResources。我对这种行为感到困惑。我不知道为什么???。可能与hi
现在,如果有人能帮我找到这个问题的天才解决方案,我将不胜感激。 上述实体以及调用JPA entity manager的find方法的代码段如下:
事件到实体:
事件分配给实体的资源:
通过提示调用实体管理器的find方法的代码段:
在修改了我的代码并对这个问题进行了长时间的思考之后,我想到了以下原因:
此问题可能与hibernate限制同时加载多个集合有关。由于我的ORM是hibernate,它可能会在将我的ORM获取到时造成这样的问题。
更多详细信息:Hibernate在一次查询获取多个行李时引发以下异常:
org.hibernate.loader.MultipleBagFetchException:无法同时执行 取多个包
使用NamedGraph可能会导致hibernate基于错误的外部左连接创建查询,这会导致获取冗余数据或无效数据 我的理解是hibernate创建查询,然后从数据库中获取行列表。每一行都包含所有数据:事件+与会者+资源,因此无法跟踪列表中的实体数量。 我不知道这在所有情况下都是可能的,但我用集合来解决这个问题。 请记住,在使用集合时,需要实现equals(和hashCode)方法
@Entity
@Table(name = "CALT_EVENT")
@SequenceGenerator(name = "seq", sequenceName = "seq_cal_event", allocationSize = 1)
@NamedEntityGraph(name = "loadGraph",
attributeNodes = {
@NamedAttributeNode(value = "attendees", subgraph = "attendees"),
@NamedAttributeNode(value = "assignedResources", subgraph = "assignedResources")
},
subgraphs = {
@NamedSubgraph(name = "attendees", attributeNodes = {@NamedAttributeNode("departmentAttendee"), @NamedAttributeNode(value = "personAttendee")}),
@NamedSubgraph(name = "assignedResources", attributeNodes = @NamedAttributeNode("resourceTO"))
}
)
})
public class EventTO {
private List<EventAttendeeTO> attendees = new ArrayList<EventAttendeeTO>();
private List<EventAssignedResourceTO> assignedResources = new ArrayList<EventAssignedResourceTO>();
/**
* @return the attendeesTOList
*/
@OneToMany(mappedBy = "eventTO", cascade = CascadeType.ALL, orphanRemoval = true)
public List<EventAttendeeTO> getAttendees() {
return attendees;
}
/**
* @param attendees the attendeesTOList to set
*/
public void setAttendees(List<EventAttendeeTO> attendees) {
if (attendees != null) {
this.attendees = attendees;
}
}
/**
* @return the assignedResourceTOList
*/
@OneToMany(cascade = CascadeType.ALL, mappedBy = "eventTO", orphanRemoval = true)
public List<EventAssignedResourceTO> getAssignedResources() {
return assignedResources;
}
/**
* @param assignedResources the assignedResourceTOList to set
*/
public void setAssignedResources(List<EventAssignedResourceTO> assignedResources) {
if (assignedResources != null) {
this.assignedResources = assignedResources;
}
}
}
@Entity
@Table(name = "CALT_EVENT_ATTENDEES")
@SequenceGenerator(name = "seq", sequenceName = "seq_cal_event_attendees", allocationSize = 1)
public class EventAttendeeTO extends RecordableExtEntityTO {
private EventTO eventTO;
private PersonTO personAttendee;
private DepartmentTO departmentAttendee;
/**
* @return the eventTO
*/
@JSON(serialize = false)
@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "EAT_EVN_ID", nullable = false)
public EventTO getEventTO() {
return eventTO;
}
/**
* @param eventTO
* the eventTO to set
*/
public void setEventTO(EventTO eventTO) {
this.eventTO = eventTO;
}
/**
* @return the attendee
*/
@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "EAT_PER_ID")
public PersonTO getPersonAttendee() {
return personAttendee;
}
/**
* @param personAttendee
* the personAttendee to set
*/
public void setPersonAttendee(PersonTO personAttendee) {
this.personAttendee = personAttendee;
if (personAttendee != null) {
this.perId = personAttendee.getId();
}
}
}
@Entity
@Table(name = "CALT_EVENT_ASSIGNED_RESOURCE")
@SequenceGenerator(name = "seq", sequenceName = "seq_cal_event_assigned_res", allocationSize = 1)
public class EventAssignedResourceTO extends ExtEntityTO {
private EventTO eventTO;
private EventResourceTO resourceTO;
/**
* @return the eventTO
*/
@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "EAR_EVN_ID", nullable = false)
public EventTO getEventTO() {
return eventTO;
}
/**
* @param eventTO
* the eventTO to set
*/
public void setEventTO(EventTO eventTO) {
this.eventTO = eventTO;
}
/**
* @return the resourceTO
*/
@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "EAR_ERS_ID")
public EventResourceTO getResourceTO() {
return resourceTO;
}
/**
* @param resourceTO
* the resourceTO to set
*/
public void setResourceTO(EventResourceTO resourceTO) {
this.resourceTO = resourceTO;
}
}
try {
EntityGraph graph = this.em.getEntityGraph("loadGraph");
Map hints = new HashMap();
hints.put("javax.persistence.fetchgraph", graph);
return em.find(EventTO.class, id, hints);
} catch (Exception e) {
new DAOException(e);
}