【问题标题】:LazyInitializationException in selectManyCheckbox on @ManyToMany(fetch=LAZY)@ManyToMany(fetch=LAZY) 上的 selectManyCheckbox 中的 LazyInitializationException
【发布时间】:2015-07-18 03:35:29
【问题描述】:

当您需要填充 JPA M:N 关系时,处理多个 chackbox 的最佳方法是什么……例如,我有一个 JPA 实体硬件和实体连接。

硬件有一套连接性:

private Set<Connectivity> connectivities = new HashSet<Connectivity>(0);

并且有一个像这样的setter和getter:

@ManyToMany(fetch = FetchType.LAZY, cascade = { CascadeType.PERSIST, CascadeType.REFRESH }, mappedBy = "hwProviders")
    public Set<Connectivity> getConnectivities() {
        return this.connectivities;
    }

    public void setConnectivities(Set<Connectivity> connectivities) {
        this.connectivities = connectivities;
    }

我在我拥有的 gui 中使用 JSF2.2 和 primefaces 5.3:

<p:selectManyCheckbox id="connectivity" value="#{hardware.connectivities}" converter="omnifaces.SelectItemsConverter" layout="pageDirection">
     <f:selectItems value="#{connectivityes}" var="connect" itemValue="#{connect}" itemLabel="#{connect.name}"/>
</p:selectManyCheckbox>

即使我在渲染视图之前调用强制加载集合,我也遇到延迟异常的问题:

hardware.getConnectivities().size();

关于如何处理这种情况的任何建议?

我正在使用omnifaces进行实体转换。

Tnx to BalusC 我已经成功地加载了,但我仍然有保存的问题。当我选择复选框并提交表单时,我认为在转换中会出现惰性异常:

16:34:50,538 SEVERE [javax.enterprise.resource.webcontainer.jsf.context] (default task-12) org.hibernate.LazyInitializationException: failed to lazily initialize a collection, could not initialize proxy - no Session
    at org.hibernate.collection.internal.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:575)
    at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:214)
    at org.hibernate.collection.internal.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:554)
    at org.hibernate.collection.internal.PersistentSet.add(PersistentSet.java:202)
    at com.sun.faces.renderkit.html_basic.MenuRenderer.convertSelectManyValuesForModel(MenuRenderer.java:381)
    at com.sun.faces.renderkit.html_basic.MenuRenderer.convertSelectManyValue(MenuRenderer.java:128)
    at com.sun.faces.renderkit.html_basic.MenuRenderer.getConvertedValue(MenuRenderer.java:314)
    at org.primefaces.component.selectmanycheckbox.SelectManyCheckboxRenderer.getConvertedValue(SelectManyCheckboxRenderer.java:39)
    at javax.faces.component.UIInput.getConvertedValue(UIInput.java:1045)
    at javax.faces.component.UIInput.validate(UIInput.java:975)
    at javax.faces.component.UIInput.executeValidate(UIInput.java:1248)
    at javax.faces.component.UIInput.processValidators(UIInput.java:712)
    at javax.faces.component.UIForm.processValidators(UIForm.java:253)
    at javax.faces.component.UIComponentBase.processValidators(UIComponentBase.java:1260)
    at javax.faces.component.UIComponentBase.processValidators(UIComponentBase.java:1260)
    at javax.faces.component.UIViewRoot.processValidators(UIViewRoot.java:1195)
    at com.sun.faces.lifecycle.ProcessValidationsPhase.execute(ProcessValidationsPhase.java:76)
    at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
    at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:198)
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:646)
    at io.undertow.servlet.handlers.ServletHandler.handleRequest(ServletHandler.java:85)
    at io.undertow.servlet.handlers.FilterHandler$FilterChainImpl.doFilter(FilterHandler.java:130)
    at si.arctur.filter.SessionFilter.doFilter(SessionFilter.java:76)
    at io.undertow.servlet.core.ManagedFilter.doFilter(ManagedFilter.java:60)
    at io.undertow.servlet.handlers.FilterHandler$FilterChainImpl.doFilter(FilterHandler.java:132)
    at io.undertow.servlet.handlers.FilterHandler.handleRequest(FilterHandler.java:85)
    at io.undertow.servlet.handlers.security.ServletSecurityRoleHandler.handleRequest(ServletSecurityRoleHandler.java:61)
    at io.undertow.servlet.handlers.ServletDispatchingHandler.handleRequest(ServletDispatchingHandler.java:36)
    at org.wildfly.extension.undertow.security.SecurityContextAssociationHandler.handleRequest(SecurityContextAssociationHandler.java:78)
    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
    at io.undertow.servlet.handlers.security.SSLInformationAssociationHandler.handleRequest(SSLInformationAssociationHandler.java:131)
    at io.undertow.servlet.handlers.security.ServletAuthenticationCallHandler.handleRequest(ServletAuthenticationCallHandler.java:56)
    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
    at io.undertow.security.handlers.AbstractConfidentialityHandler.handleRequest(AbstractConfidentialityHandler.java:45)
    at io.undertow.servlet.handlers.security.ServletConfidentialityConstraintHandler.handleRequest(ServletConfidentialityConstraintHandler.java:63)
    at io.undertow.security.handlers.AuthenticationMechanismsHandler.handleRequest(AuthenticationMechanismsHandler.java:58)
    at io.undertow.servlet.handlers.security.CachedAuthenticatedSessionHandler.handleRequest(CachedAuthenticatedSessionHandler.java:70)
    at io.undertow.security.handlers.SecurityInitialHandler.handleRequest(SecurityInitialHandler.java:76)
    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
    at org.wildfly.extension.undertow.security.jacc.JACCContextIdHandler.handleRequest(JACCContextIdHandler.java:61)
    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
    at io.undertow.servlet.handlers.ServletInitialHandler.handleFirstRequest(ServletInitialHandler.java:261)
    at io.undertow.servlet.handlers.ServletInitialHandler.dispatchRequest(ServletInitialHandler.java:247)
    at io.undertow.servlet.handlers.ServletInitialHandler.access$000(ServletInitialHandler.java:76)
    at io.undertow.servlet.handlers.ServletInitialHandler$1.handleRequest(ServletInitialHandler.java:166)
    at io.undertow.server.Connectors.executeRootHandler(Connectors.java:197)
    at io.undertow.server.HttpServerExchange$1.run(HttpServerExchange.java:759)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)

【问题讨论】:

    标签: jsf jpa primefaces lazy-initialization selectmanycheckbox


    【解决方案1】:

    您需要在事务内部(因此,在服务方法内部)获取它,而在事务外部(因此,在例如 JSF 托管的 bean init/action 方法内部)获取它,这将因此抛出一个LazyInitializationException

    所以,你的尝试

    hardware.getConnectivities().size();
    

    必须在事务中进行。如有必要,创建一个新的服务方法,用于传递之前在另一个事务中获得的实体。

    hardwareService.fetchConnectivities(hardware);
    
    public void fetchConnectivities(Hardware hardware) {
        hardware.setConnectivities(em.merge(hardware).getConnectivities()); // Becomes managed.
        hardware.getConnectivities().size(); // Triggers lazy initialization.
    }
    

    另一种方法是为急切获取它的目的创建一个 DTO。

    然后要保存所选项目,请确保将选择组件的 collectionType 属性显式指定为标准 Java 类型,而不是让它自动发现 JPA impl 特定的延迟加载类型,例如您的特定情况下的 org.hibernate.collection.internal.PersistentSet . JSF 需要它来实例化集合,然后再用选定的项目填充它。

    <p:selectManyCheckbox ... collectionType="java.util.LinkedHashSet">
    

    另见org.hibernate.LazyInitializationException at com.sun.faces.renderkit.html_basic.MenuRenderer.convertSelectManyValuesForModel

    【讨论】:

    • 我在 ViewScoped cdi bean 的 PostConstruct 中这样做
    • 作为回答,这不在事务中。
    • 好的,当我尝试保存时,我也会遇到惰性异常......在这种情况下处理保存的正确方法是什么?
    • 只要确保它已经在事务中获取。你明白什么是交易吗?如果没有,这可能是阅读的食物:stackoverflow.com/q/18369356
    • 嗯,即使我在事务中获取它,例如在 EJB 方法中,当我尝试保存它时将它传递给托管 bean,它也会再次引发惰性异常
    【解决方案2】:

    我只能通过指定来修复它

    <f:attribute name="collectionType" value="java.util.LinkedHashSet" />
    

    【讨论】:

    • 那么您已经在另一个答案中提到的事务中
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