JPA 2.1 Eager Fetch 属性
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【中文标题】JPA 2.1 Eager Fetch 属性【英文标题】:JPA 2.1 Eager Fetch Attribute 【发布时间】:2014-04-09 08:00:45 【问题描述】:我有一个属性(元数据中的creationTimestamp),我将其注释为延迟加载。不,我需要一个实体来加载渴望。我尝试使用获取图表但没有成功。是否有类似 JOIN FETCH 的功能可以用来在查询中获取它?
我将 Wildfly 与捆绑的休眠一起使用。
当我尝试使用 fetch graph 获取它时,我得到了 hibernate 找不到 id 字段的异常。此字段在实体库中(受保护)。
@NamedQueries( @NamedQuery(name = ChatMessage.FIND_BY_CHAT_TIME, query = "SELECT m FROM ChatMessage m "
+ "WHERE m.chat=:chat "
+ "AND m.creationTimestamp > :index ORDER BY m.creationTimestamp") )
@NamedEntityGraph(
name = ChatMessage.GRAPH_FETCH_ALL,
attributeNodes = @NamedAttributeNode("id"), @NamedAttributeNode("player"), @NamedAttributeNode("text"), @NamedAttributeNode("creationTimestamp")
)
public class ChatMessage extends EntityBase
@MappedSuperclass
public abstract class EntityBase extends MetaData
private static final long serialVersionUID = -5579667581450362176L;
public static final String FETCH_GRAPH_HINT = "javax.persistence.fetchgraph";
@Id
@Column(length = 36)
protected String id = java.util.UUID.randomUUID().toString();
@MappedSuperclass
public class MetaData implements Serializable
private static final long serialVersionUID = 8870539357817188030L;
@Version
private long version;
@Temporal(TemporalType.TIMESTAMP)
@Column(nullable = false, updatable = false)
@Basic(fetch=FetchType.LAZY)
protected Calendar creationTimestamp;
@Temporal(TemporalType.TIMESTAMP)
@Column(nullable = false)
@Basic(fetch=FetchType.LAZY)
private Calendar updateTimestamp;
导致此异常:
Caused by: java.lang.IllegalArgumentException: Unable to locate Attribute with the the given name [id] on this ManagedType [ChatMessage]
at org.hibernate.jpa.internal.metamodel.AbstractManagedType.checkNotNull(AbstractManagedType.java:144)
at org.hibernate.jpa.internal.metamodel.AbstractManagedType.getDeclaredAttribute(AbstractManagedType.java:137)
at org.hibernate.jpa.graph.internal.EntityGraphImpl.resolveAttribute(EntityGraphImpl.java:139)
at org.hibernate.jpa.graph.internal.AbstractGraphNode.buildAttributeNode(AbstractGraphNode.java:119)
at org.hibernate.jpa.graph.internal.AbstractGraphNode.addAttribute(AbstractGraphNode.java:114)
at org.hibernate.jpa.internal.EntityManagerFactoryImpl.applyNamedAttributeNodes(EntityManagerFactoryImpl.java:279)
at org.hibernate.jpa.internal.EntityManagerFactoryImpl.applyNamedEntityGraphs(EntityManagerFactoryImpl.java:266)
at org.hibernate.jpa.internal.EntityManagerFactoryImpl.<init>(EntityManagerFactoryImpl.java:173)
at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl$4.perform(EntityManagerFactoryBuilderImpl.java:865)
at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl$4.perform(EntityManagerFactoryBuilderImpl.java:843)
at org.hibernate.boot.registry.classloading.internal.ClassLoaderServiceImpl.withTccl(ClassLoaderServiceImpl.java:399)
at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:842)
at org.hibernate.jpa.HibernatePersistenceProvider.createEntityManagerFactory(HibernatePersistenceProvider.java:73)
有没有办法像 fetch join 一样获取属性?还是我必须以其他方式引用获取图?
最好的问候, 米
【问题讨论】:
【参考方案1】:看起来子类的属性必须以不同的方式引用:
@NamedEntityGraph(
name = ChatMessage.GRAPH_FETCH_ALL,
attributeNodes = @NamedAttributeNode("player"), @NamedAttributeNode("text")
, subgraphs=@NamedSubgraph(name="MetaData.subgraph", attributeNodes=@NamedAttributeNode("id"), @NamedAttributeNode("creationTimestamp"))
)
【讨论】:
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