在计算字段上摆脱 LazyInitializationException 的最佳方法是什么？

【问题标题】：What is best way to get rid of LazyInitializationException on calculated fields?在计算字段上摆脱 LazyInitializationException 的最佳方法是什么？
【发布时间】：2017-10-16 17:29:45
【问题描述】：

嗨，我对 Hibernate 还很陌生，我遇到了 LazyInitiationException。请给我一个如何解决这个问题的例子。我已经计算了导出字段，并在其上添加了@transient，但似乎不起作用。请告诉我如何使用它并在 Jsf 中传递它。

另外，如果 DTO 是要走的路。你能给我一个如何做 DTO 的例子吗，因为这不是我可以从 db 获得并创建一个视图的东西。任何帮助将不胜感激？

这是我的 jsf：

<pe:dynaFormControl type="EMPLOYEE_VALUE" for="employeeDyna#{tab.id}-#{subtab.id}">
        <p:autoComplete id="employeeDyna#{tab.id}-#{subtab.id}" scrollHeight="250" value="#{data.entityValue.employee}" converter="#{entityConverter}" completeMethod="#{autoCompletionBean.employeeAutoCompleteList}"
            var="emp" itemLabel="#{emp.getFullName()}" itemValue="#{emp}" maxResults="500" dropdown="true" forceSelection="true" minQueryLength="2" queryDelay="800" required="#{data.cf.derived}" requiredMessage="#{secondEmployeeBean.getRequiredMessage(data.cf.name)}"
            disabled="#{empty bean_Data.selectedAccount and !PARAM_OPTIONAL}">
            <f:attribute name="selectedAccount" value="#{bean_Data.selectedAccount}" />
        </p:autoComplete>
    </pe:dynaFormControl>

这是我的实体类：

import java.beans.Transient;    

@Entity
@Table(name = "EMPLOYEE")
public class Employee extends AbstractIdentity {

    @Enumerated(EnumType.ORDINAL)
    @Column(name = "COMPANY_TYPE_CODE", insertable = false, updatable = false)
    @Getter
    private EEntityType companyTypeCode;


    @Any(metaColumn = @Column(name = "COMPANY_TYPE_CODE"))
    @AnyMetaDef(idType = "long", metaType = "long",
    metaValues = {
        @MetaValue(targetEntity = CLass1.class, value = EEntityType.CLass1_CODE),
        @MetaValue(targetEntity = CLass2.class, value = EEntityType.CLass2_CODE),
        @MetaValue(targetEntity = CLass3.class, value = EEntityType.CLass3_CODE),
        @MetaValue(targetEntity = CLass4.class, value = EEntityType.CLass4_CODE),
    })
    @JoinColumn(name = "COMPANY_ID")
    @BatchSize(size = AppConfig.BATCH_SIZE)
    @Getter
    @Setter
    private AbstractCompany entityCompany;

    @Transient
     public String getFullName(boolean withCompany) {
        StringBuffer stringBuffer = new StringBuffer(getName());

        if (withCompany) {

            if (null != getEntityCompany() && !getEntityCompany().getName().trim().equals("")) {
                stringBuffer.append(" - ");
                stringBuffer.append(getEntityCompany().getName());
            }
        }

        return stringBuffer.toString();
    }

}

这是错误：

javax.el.ELException: /includes/components/customFieldEditView.xhtml @76,70 itemLabel="#{emp.getFullName()}": org.hibernate.LazyInitializationException: could not initialize proxy - no Session
    at com.sun.faces.facelets.el.TagValueExpression.getValue(TagValueExpression.java:114)
    at javax.faces.component.ComponentStateHelper.eval(ComponentStateHelper.java:194)
    at org.primefaces.component.autocomplete.AutoComplete.getItemLabel(AutoComplete.java:162)
    at org.primefaces.component.autocomplete.AutoCompleteRenderer.encodeInput(AutoCompleteRenderer.java:212)
    at org.primefaces.component.autocomplete.AutoCompleteRenderer.encodeSingleMarkup(AutoCompleteRenderer.java:154)
    at org.primefaces.component.autocomplete.AutoCompleteRenderer.encodeMarkup(AutoCompleteRenderer.java:137)
    at org.primefaces.component.autocomplete.AutoCompleteRenderer.encodeEnd(AutoCompleteRenderer.java:115)
    at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:920)
    at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1863)
    at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1859)
    at org.primefaces.extensions.component.dynaform.DynaFormRenderer.encodeBody(DynaFormRenderer.java:283)
    at org.primefaces.extensions.component.dynaform.DynaFormRenderer.encodeMarkup(DynaFormRenderer.java:115)
    at org.primefaces.extensions.component.dynaform.DynaFormRenderer.encodeEnd(DynaFormRenderer.java:80)
    at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:920)
    at org.primefaces.renderkit.CoreRenderer.renderChild(CoreRenderer.java:89)
    at org.primefaces.renderkit.CoreRenderer.renderChildren(CoreRenderer.java:72)
    at org.primefaces.component.fieldset.FieldsetRenderer.encodeContent(FieldsetRenderer.java:94)
    at org.primefaces.component.fieldset.FieldsetRenderer.encodeMarkup(FieldsetRenderer.java:76)
    at org.primefaces.component.fieldset.FieldsetRenderer.encodeEnd(FieldsetRenderer.java:47)
    at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:920)
    at org.primefaces.renderkit.CoreRenderer.renderChild(CoreRenderer.java:89)
    at org.primefaces.renderkit.CoreRenderer.renderChildren(CoreRenderer.java:72)
    at org.primefaces.component.fieldset.FieldsetRenderer.encodeContent(FieldsetRenderer.java:94)
    at org.primefaces.component.fieldset.FieldsetRenderer.encodeMarkup(FieldsetRenderer.java:76)
    at org.primefaces.component.fieldset.FieldsetRenderer.encodeEnd(FieldsetRenderer.java:47)
    at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:920)
    at org.primefaces.renderkit.CoreRenderer.renderChild(CoreRenderer.java:89)
    at org.primefaces.renderkit.CoreRenderer.renderChildren(CoreRenderer.java:72)
    at org.primefaces.component.panelgrid.PanelGridRenderer.encodeRow(PanelGridRenderer.java:196)
    at org.primefaces.component.panelgrid.PanelGridRenderer.encodeStaticBody(PanelGridRenderer.java:151)
    at org.primefaces.component.panelgrid.PanelGridRenderer.encodeTableBody(PanelGridRenderer.java:104)
    at org.primefaces.component.panelgrid.PanelGridRenderer.encodeTableLayout(PanelGridRenderer.java:65)
    at org.primefaces.component.panelgrid.PanelGridRenderer.encodeEnd(PanelGridRenderer.java:37)
    at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:920)
    at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1863)
    at javax.faces.render.Renderer.encodeChildren(Renderer.java:176)
    at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:890)
    at org.primefaces.renderkit.CoreRenderer.renderChild(CoreRenderer.java:85)
    at org.primefaces.renderkit.CoreRenderer.renderChildren(CoreRenderer.java:72)
    at org.primefaces.component.fieldset.FieldsetRenderer.encodeContent(FieldsetRenderer.java:94)
    at org.primefaces.component.fieldset.FieldsetRenderer.encodeMarkup(FieldsetRenderer.java:76)
    at org.primefaces.component.fieldset.FieldsetRenderer.encodeEnd(FieldsetRenderer.java:47)
    at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:920)
    at org.primefaces.renderkit.CoreRenderer.renderChild(CoreRenderer.java:89)
    at org.primefaces.renderkit.CoreRenderer.renderChildren(CoreRenderer.java:72)
    at org.primefaces.component.panel.PanelRenderer.encodeContent(PanelRenderer.java:206)
    at org.primefaces.component.panel.PanelRenderer.encodeMarkup(PanelRenderer.java:123)
    at org.primefaces.component.panel.PanelRenderer.encodeEnd(PanelRenderer.java:58)
    at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:920)
    at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1863)
    at com.sun.faces.context.PartialViewContextImpl$PhaseAwareVisitCallback.visit(PartialViewContextImpl.java:582)
    at com.sun.faces.component.visit.PartialVisitContext.invokeVisitCallback(PartialVisitContext.java:183)
    at javax.faces.component.UIComponent.visitTree(UIComponent.java:1689)
    at javax.faces.component.UIComponent.visitTree(UIComponent.java:1700)
    at javax.faces.component.UIComponent.visitTree(UIComponent.java:1700)
    at javax.faces.component.UIComponent.visitTree(UIComponent.java:1700)
    at javax.faces.component.UIComponent.visitTree(UIComponent.java:1700)
    at com.sun.faces.context.PartialViewContextImpl.processComponents(PartialViewContextImpl.java:403)
    at com.sun.faces.context.PartialViewContextImpl.processPartial(PartialViewContextImpl.java:322)
    at org.primefaces.context.PrimePartialViewContext.processPartial(PrimePartialViewContext.java:57)
    at javax.faces.context.PartialViewContextWrapper.processPartial(PartialViewContextWrapper.java:219)
    at org.omnifaces.context.OmniPartialViewContext.processPartial(OmniPartialViewContext.java:143)
    at javax.faces.context.PartialViewContextWrapper.processPartial(PartialViewContextWrapper.java:219)
    at javax.faces.component.UIViewRoot.encodeChildren(UIViewRoot.java:1004)
    at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1856)
    at com.sun.faces.application.view.FaceletViewHandlingStrategy.renderView(FaceletViewHandlingStrategy.java:432)
    at com.sun.faces.application.view.MultiViewHandler.renderView(MultiViewHandler.java:134)
    at javax.faces.application.ViewHandlerWrapper.renderView(ViewHandlerWrapper.java:337)
    at javax.faces.application.ViewHandlerWrapper.renderView(ViewHandlerWrapper.java:337)
    at javax.faces.application.ViewHandlerWrapper.renderView(ViewHandlerWrapper.java:337)
    at javax.faces.application.ViewHandlerWrapper.renderView(ViewHandlerWrapper.java:337)
    at javax.faces.application.ViewHandlerWrapper.renderView(ViewHandlerWrapper.java:337)
    at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:120)
    at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
    at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:219)
    at org.springframework.faces.support.LifecycleWrapper.render(LifecycleWrapper.java:54)
    at org.springframework.faces.webflow.JsfView.render(JsfView.java:87)
    at org.springframework.webflow.engine.ViewState.render(ViewState.java:293)
    at org.springframework.webflow.engine.ViewState.doEnter(ViewState.java:185)
    at org.springframework.webflow.engine.State.enter(State.java:194)
    at org.springframework.webflow.engine.Transition.execute(Transition.java:228)
    at org.springframework.webflow.engine.DecisionState.doEnter(DecisionState.java:51)
    at org.springframework.webflow.engine.State.enter(State.java:194)
    at org.springframework.webflow.engine.Flow.start(Flow.java:527)
    at org.springframework.webflow.engine.impl.FlowExecutionImpl.start(FlowExecutionImpl.java:368)
    at org.springframework.webflow.engine.impl.RequestControlContextImpl.start(RequestControlContextImpl.java:234)
    at org.springframework.webflow.engine.SubflowState.doEnter(SubflowState.java:101)
    at org.springframework.webflow.engine.State.enter(State.java:194)
    at org.springframework.webflow.engine.Transition.execute(Transition.java:228)
    at org.springframework.webflow.engine.DecisionState.doEnter(DecisionState.java:51)
    at org.springframework.webflow.engine.State.enter(State.java:194)
    at org.springframework.webflow.engine.Transition.execute(Transition.java:228)
    at org.springframework.webflow.engine.impl.FlowExecutionImpl.execute(FlowExecutionImpl.java:395)
    at org.springframework.webflow.engine.impl.RequestControlContextImpl.execute(RequestControlContextImpl.java:214)
    at org.springframework.webflow.engine.Flow.handleEvent(Flow.java:552)
    at org.springframework.webflow.engine.impl.FlowExecutionImpl.handleEvent(FlowExecutionImpl.java:390)
    at org.springframework.webflow.engine.impl.RequestControlContextImpl.handleEvent(RequestControlContextImpl.java:210)
    at org.springframework.webflow.engine.ViewState.handleEvent(ViewState.java:231)
    at org.springframework.webflow.engine.ViewState.resume(ViewState.java:195)
    at org.springframework.webflow.engine.Flow.resume(Flow.java:537)
    at org.springframework.webflow.engine.impl.FlowExecutionImpl.resume(FlowExecutionImpl.java:259)
    at org.springframework.webflow.executor.FlowExecutorImpl.resumeExecution(FlowExecutorImpl.java:169)
    at org.springframework.webflow.mvc.servlet.FlowHandlerAdapter.handle(FlowHandlerAdapter.java:253)
    at org.springframework.faces.webflow.JsfFlowHandlerAdapter.handle(JsfFlowHandlerAdapter.java:57)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:963)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:897)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)
    at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:872)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:648)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:230)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
    at org.primefaces.webapp.filter.FileUploadFilter.doFilter(FileUploadFilter.java:100)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
    at com.abc.web.filter.abcWebAppFilter.doFilter(abcWebAppFilter.java:64)
    at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:346)
    at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:262)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:317)
    at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:127)
    at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:91)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
    at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:114)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
    at org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:137)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
    at org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:111)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
    at org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:170)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
    at org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:63)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
    at org.springframework.security.web.session.ConcurrentSessionFilter.doFilter(ConcurrentSessionFilter.java:155)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
    at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:200)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
    at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:116)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
    at org.springframework.security.web.header.HeaderWriterFilter.doFilterInternal(HeaderWriterFilter.java:64)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
    at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:82)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
    at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:105)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
    at org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter.doFilterInternal(WebAsyncManagerIntegrationFilter.java:56)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
    at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:214)
    at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:177)
    at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:346)
    at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:262)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
    at org.springframework.orm.jpa.support.OpenEntityManagerInViewFilter.doFilterInternal(OpenEntityManagerInViewFilter.java:178)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
    at org.apache.logging.log4j.web.Log4jServletFilter.doFilter(Log4jServletFilter.java:71)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:108)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:620)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:349)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:783)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:789)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1455)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:748)
Caused by: javax.el.ELException: org.hibernate.LazyInitializationException: could not initialize proxy - no Session
    at javax.el.BeanELResolver.invoke(BeanELResolver.java:164)
    at javax.el.CompositeELResolver.invoke(CompositeELResolver.java:79)
    at org.apache.el.parser.AstValue.getValue(AstValue.java:159)
    at org.apache.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:184)
    at com.sun.faces.facelets.el.TagValueExpression.getValue(TagValueExpression.java:109)
    ... 182 more

【问题讨论】：

    标签： java hibernate jsf lazy-initialization


    【解决方案1】：

    我的问题是：你的Employee 实体和你的AbstractCompany 是什么关系？作为一个单值对象（不是集合类型），我假设它可以是一对一或多对一的。

    从堆栈跟踪来看，您有延迟加载问题。默认情况下，无论关联映射如何，Hibernate 都会执行延迟加载。

    默认情况下，Hibernate 对集合使用惰性选择获取和 单值关联的惰性代理获取。这些默认值 对大多数应用程序中的大多数关联都有意义。

    我认为您的代码中的问题是： getEntityCompany().getName() 在您的 getFullName 方法中。您试图访问延迟加载实体 (AbstractCompany) 的属性。一旦您在 Hibernate 会话/事务之外，您将无法执行此操作。

    你有两个选择：

    1) EAGER 加载关系

    @ManyToOne(fetch=FetchType.EAGER)
private AbstractCompany entityCompany;

    或者如果你使用一对一（这就是为什么我首先问Employee和AbstractCompany之间的关系类型是什么）

    @OneToOne(fetch=FetchType.EAGER)
private AbstractCompany entityCompany;

    2) 在 Hibernate 会话中加载关系

    Hibernate.initialize(employee.getEntityCompany());

    【讨论】：

    • 对不起，我错过了一些代码。请查看更新的。
    • 尝试将此添加到您的 @Any 注释 fetch=FetchType.EAGER
    • 除了EAGER还有其他解决方案吗？不确定我是否想使用 Eager，因为它可能会影响性能。
    • 那么你就剩下选项 2 或者你可以按照另一个答案的建议 - 建造一个门面。
    • 我只是不知道如何构建立面。可以举个例子吗？
    【解决方案2】：

    您收到此异常是因为您尝试在用于检索数据的事务之外加载字段。

    当休眠检索数据时，它将为字段创建代理实体。当第一次访问这些代理之一时，休眠将发送一个新请求以获取此特定数据。问题是，一旦事务关闭，hibernate 就无法做到这一点。

    您需要确保您的数据库请求也加载了您感兴趣的字段（急切的注释或加入查询），或者您需要事先检索此数据（在事务中访问它或初始化代理，仍然在交易中）。

    由于您要将此数据发送到视图，因此我建议您使用外观。 外观将包含构建页面所需的所有数据。因此，在您拥有交易的服务中，将您的结果转换为您的页面将能够使用的外观。

    外观几乎只是一个 POJO，用于为您的视图存储数据。

    【讨论】：

    • 啊。你能给我一个外观的例子以及如何在 UI 中调用它吗？
    • 正如我所说的门面是 POJO，即只是成员和 getter setter。你将外观传递给你的视图，就像你做你的实体一样。实际上你使用你的外观就像你使用你的实体一样。唯一的区别是您正在抽象与视图相关的实体。
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