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在学习 Hibernate 时，我遇到了这个问题。从合同表中进行查询（我想在数据库中列出可用的合同）。我无法在我的 jsp 中显示关税实体字段（例如 Contract.Tariff.title）。同时，在实体 Contract 中，Tariff 上明确指定了 JoinColumn。合同中的选项列表正确显示。由于合同和关税实体中的选项列表，是否会出现此问题。下面附上图表和代码。

架构

注意到实体和架构之间的差异。更新了实体以匹配架构。(24.07.20)

选项实体代码：

   @Entity
@Table(name = "option_table")
public class Option implements Serializable {
    @Id
    @Column(name = "option_id", unique = true, nullable = false)
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer optionId;

    @Column(name = "title")
    private String title;

    @Column(name = "price")
    private Integer price;

    @Column(name = "cost")
    private Integer cost;
        //getters,setters

关税实体代码：

    Entity
@Table(name = "tariff_table")
public class Tariff implements Serializable {
    @Id
    @Column(name = "tariff_id", unique = true, nullable = false)
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer tariffId;

    @Column(name = "title")
    private String title;

    @Column(name = "price")
    private Double price;


    @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
   @JoinTable( name = "tariff_option",
                joinColumns = {@JoinColumn(name = "tariff_id")},
                inverseJoinColumns = {@JoinColumn(name = "option_id")})
    private List<Option> optionList;enter code here
        //getters,setters

合同实体代码：

@Entity
@Table(name = "contract_table")
public class Contract implements Serializable {
    @Id
    @Column(name = "contract_id", unique = true, nullable = false)
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer contractId;

    @Column(name = "number")
    private String number;


    @OneToOne(fetch = FetchType.LAZY, cascade = CascadeType.ALL)
    @JoinColumn(name = "tariff_id", referencedColumnName = "tariff_id")
    private Tariff contractTariff;

    @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
    @JoinTable( name = "contract_option",
            joinColumns = {@JoinColumn(name = "contract_id")},
            inverseJoinColumns = {@JoinColumn(name = "option_id")})
    private List<Option> contractOptionList;
     //getters,setters

Tomcat日志：

22-Jul-2020 19:16:41.640 INFO [RMI TCP Connection(3)-127.0.0.1] org.apache.catalina.core.ApplicationContext.log 1 Spring WebApplicationInitializers detected on classpath
22-Jul-2020 19:16:41.858 INFO [RMI TCP Connection(3)-127.0.0.1] org.apache.catalina.core.ApplicationContext.log Initializing Spring root WebApplicationContext
22-Jul-2020 19:16:58.441 INFO [RMI TCP Connection(3)-127.0.0.1] org.apache.catalina.core.ApplicationContext.log Initializing Spring DispatcherServlet 'dispatcher'
22-Jul-2020 19:17:44.898 SEVERE [http-nio-8080-exec-2] org.apache.catalina.core.ApplicationDispatcher.invoke Servlet.service() for servlet [jsp] threw exception
    org.hibernate.LazyInitializationException: could not initialize proxy [ecare.domain.Tariff#1] - no Session
        at org.hibernate.proxy.AbstractLazyInitializer.initialize(AbstractLazyInitializer.java:170)
        at org.hibernate.proxy.AbstractLazyInitializer.getImplementation(AbstractLazyInitializer.java:310)
        at org.hibernate.proxy.pojo.bytebuddy.ByteBuddyInterceptor.intercept(ByteBuddyInterceptor.java:45)
        at org.hibernate.proxy.ProxyConfiguration$InterceptorDispatcher.intercept(ProxyConfiguration.java:95)
        at ecare.domain.Tariff$HibernateProxy$qthLTppY.toString(Unknown Source)
        at org.apache.el.lang.ELSupport.coerceToString(ELSupport.java:492)
        at org.apache.el.lang.ELSupport.coerceToType(ELSupport.java:524)
        at org.apache.el.ExpressionFactoryImpl.coerceToType(ExpressionFactoryImpl.java:47)
        at javax.el.ELContext.convertToType(ELContext.java:304)
        at org.apache.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:192)
        at org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate(PageContextImpl.java:701)
        at org.apache.jsp.WEB_002dINF.views.contract_jsp._jspx_meth_c_005fforEach_005f0(contract_jsp.java:211)
        at org.apache.jsp.WEB_002dINF.views.contract_jsp._jspService(contract_jsp.java:160)
        at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:71)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
        at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:477)
        at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:385)
        at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:329)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:712)
        at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:459)
        at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:384)
        at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:312)
        at org.springframework.web.servlet.view.InternalResourceView.renderMergedOutputModel(InternalResourceView.java:171)
        at org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:316)
        at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1373)
        at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1118)
        at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1057)
        at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943)
        at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
        at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:634)
        at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
        at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139)
36:                         <p>Contract Info</p>
37:                         <h3>Contract id: ${contract.tariff}</h3>
38:                         <h3>Contract option list:</h3>
39:                         <h3></h3>
40: 


Stacktrace:] with root cause
    org.hibernate.LazyInitializationException: could not initialize proxy [ecare.domain.Tariff#1] - no Session
        at org.hibernate.proxy.AbstractLazyInitializer.initialize(AbstractLazyInitializer.java:170)
        at org.hibernate.proxy.AbstractLazyInitializer.getImplementation(AbstractLazyInitializer.java:310)
        at org.hibernate.proxy.pojo.bytebuddy.ByteBuddyInterceptor.intercept(ByteBuddyInterceptor.java:45)
        at org.hibernate.proxy.ProxyConfiguration$InterceptorDispatcher.intercept(ProxyConfiguration.java:95)
        at ecare.domain.Tariff$HibernateProxy$qthLTppY.toString(Unknown Source)
        at org.apache.el.lang.ELSupport.coerceToString(ELSupport.java:492)
        at org.apache.el.lang.ELSupport.coerceToType(ELSupport.java:524)
        at org.apache.el.ExpressionFactoryImpl.coerceToType(ExpressionFactoryImpl.java:47)
        at javax.el.ELContext.convertToType(ELContext.java:304)
        at org.apache.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:192)
        at org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate(PageContextImpl.java:701)
        at org.apache.jsp.WEB_002dINF.views.contract_jsp._jspx_meth_c_005fforEach_005f0(contract_jsp.java:211)
        at org.apache.jsp.WEB_002dINF.views.contract_jsp._jspService(contract_jsp.java:160)
        at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:71)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
        at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:477)
        at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:385)
        at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:329)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:712)
        at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:459)
        at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:384)
        at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:312)
        at org.springframework.web.servlet.view.InternalResourceView.renderMergedOutputModel(InternalResourceView.java:171)
        at org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:316)
        at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1373)
        at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1118)
        at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1057)
        at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943)
        at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
        at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:634)
        at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
        at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
        at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:690)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
        at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:373)
        at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
        at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868)
        at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1590)
        at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
        at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
        at java.lang.Thread.run(Thread.java:748)
22-Jul-2020 19:17:44.898 SEVERE [http-nio-8080-exec-2] org.apache.catalina.core.StandardWrapperValve.invoke Servlet.service() for servlet [dispatcher] in context with path [] threw exception [Произошла ошибка при обработке [/WEB-INF/views/contract.jsp] в строке [37]

34:                 <div class="thumbnail">
35:                     <div class="caption">
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
        at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:690)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
        at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:373)
        at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
        at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868)
        at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1590)
        at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
        at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
        at java.lang.Thread.run(Thread.java:748)
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1 回答 1

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在 jps 调用 getTariff() 之前，我不确定会话是否仍然有效，因为我从未使用过 jsp 或任何类型的 Spring 模板。但是由于您的关系是 LAZY，如果会话关闭，休眠将无法加载关税。

同时，您可以在获得合同时尝试加载关税，EntityGraphs 很有用： https://docs.spring.io/spring-data/jpa/docs/current/reference/html/#jpa。实体图

在示例 77中，查询从实体中getByGroupName获取属性membersGroupInfo

于 2020-07-22T21:21:06.160 回答