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[英]LazyInitializationException using hibernate enhancement with @Basic(fetch = FetchType.LAZY)
[英]Why am I getting a LazyInitializationException when using FetchType.LAZY on one Set, but not on the other?
我在這里遇到了一個非常特殊的問題。 似乎有些Set會延遲加載,而其他的則不會,但是底層類的布局完全相同:
在Spring-boot Hibernate映射中,我有4個類:
這些是頂級類Event :
@Entity
public class Event {
// Getters, setters, etc. are omitted.
@OneToMany(fetch = FetchType.LAZY, mappedBy = "event", cascade = CascadeType.ALL)
@ElementCollection(targetClass = Question.class)
private Set<Question> questions = new HashSet<>();
@OneToMany(fetch = FetchType.LAZY, mappedBy = "event", cascade = CascadeType.ALL)
@ElementCollection(targetClass = Participant.class)
private Set<Participant> participants = new HashSet<>();
@OneToMany(fetch = FetchType.LAZY, mappedBy = "event", cascade = CascadeType.ALL)
@ElementCollection(targetClass = Run.class)
private Set<Run> runs = new HashSet<>();
}
這是鏈接到此事件根節點類的3個類:
問題 :
@Entity
public class Question {
// Getters, setters, etc. are omitted.
@ManyToOne(fetch = FetchType.LAZY)
private Event event;
}
參加者 :
@Entity
public class Participant {
// Getters, setters, etc. are omitted.
@ManyToOne(fetch = FetchType.LAZY)
private Event event;
}
運行 :
@Entity
public class Run {
// Getters, setters, etc. are omitted.
@ManyToOne(fetch = FetchType.LAZY)
private Event event;
}
當然,有一些與JPA相關的空構造函數,其他構造函數,許多Hibernate / JPA標簽和更多基礎關系,但是我堅信,這些並不會在這里有所作為。 在將Set<Run>
變量引入Event類后,開始出現問題。
運行程序,創建Event類型的對象,然后添加事件,一切正常,但是創建一個新的Run對象並將其添加到Event.runs
字段中,則在JUnit測試中出現以下錯誤:
調用event.getRuns().add(<a new 'Run' object>)
:
org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.ps.model.orm.Event.runs, could not initialize proxy - no Session
at org.hibernate.collection.internal.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:576)
at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:215)
at org.hibernate.collection.internal.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:555)
at org.hibernate.collection.internal.PersistentSet.add(PersistentSet.java:202)
at com.ps.HibernateTestApplicationTests.testRunCreation(HibernateTestApplicationTests.java:88)
at com.ps.HibernateTestApplicationTests.testAllTheThings(HibernateTestApplicationTests.java:37)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:75)
at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:86)
at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:84)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:254)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:89)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:193)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:678)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)
在這一點上,懶惰的實例似乎對我來說很糟糕。 當我將FetchType.LAZY
的@OneToMany標記的Event.runs
為FetchType.EAGER
,程序將按預期方式執行,但是我一生無法弄清楚為什么LAZY在此期間無法正常工作它適用於其他類,因為它們的結構幾乎相同。
其他人都可以使用LAZY
和 EAGER
,而這兩者都沒有,我真的看不到映射或此處的任何內容的區別,所以即使我現在只使用EAGER
類型而不是LAZY
,我也知道灰心喪氣,想知道是否發生了什么事,我可能已經看過了。
stacktrace告訴您問題所在-
無法初始化代理-沒有會話
只需確保在仍可使用會話的事務中調用event.getRuns().add(<a new 'Run' object>)
即可。
如果使用Spring只是用@Transactional
注釋方法
像這樣
@Transactional
public void doSomething(){
Event event= // get Event from DB ;
event.getRuns.add(//new Run);
//some other stuff
}
我有同樣的問題。我已經解決了這個問題,在我的web.xml文件中添加了以下代碼,希望對您有所幫助;)
<filter>
<filter-name>SpringOpenEntityManagerInViewFilter</filter-name>
<filter-class>org.springframework.orm.jpa.support.OpenEntityManagerInViewFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>SpringOpenEntityManagerInViewFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
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