Question

当我尝试从数据库中提取时，我有一个例外。

我有三个具有ManyToOne关系的实体。一个A - ＆gt;许多B，One A - ＆gt; C和一个B - ＆gt;很多D.我使用的是EAGER＆＃39; Type。但我得到例外。见下文。

第一个实体：

@Entity
@Table
public class A {

    @Id
    @Column(columnDefinition = "VARCHAR(50)", nullable = false)
    private String aId;

    @OneToMany(mappedBy = "a", targetEntity = B.class, fetch = FetchType.EAGER, cascade = CascadeType.ALL)
    private List<B> b;

    @OneToMany(mappedBy = "a", targetEntity = C.class, cascade = CascadeType.ALL)
    private List<C> c;

第二个：

@Entity
@Table
public class B {

    @Id
    @Column(columnDefinition = "VARCHAR(50)", nullable = false)
    private String bId;

    @ManyToOne(targetEntity = A.class, cascade = CascadeType.ALL)
    @JoinColumn(name = "aId", referencedColumnName = "aId")
    private A a;

    @OneToMany(mappedBy = "b", targetEntity = D.class, fetch = FetchType.EAGER, cascade = CascadeType.ALL)
    private List<D> d;

最后一个：

@Entity
@Table
public class D {

    @Id
    @Column(columnDefinition = "VARCHAR(50)", nullable = false)
    private String dId;

    @ManyToOne(targetEntity = B.class, cascade = CascadeType.ALL)
    @JoinColumn(name = "bId", referencedColumnName = "bId",)
    private B b;

当我运行查询时，我得到了这个执行：

Invocation of init method failed; nested exception is org.hibernate.loader.MultipleBagFetchException: cannot simultaneously fetch multiple bags
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1566)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:539)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:476)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:303)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:299)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194)
    at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:956)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:747)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:480)
    at org.springframework.context.annotation.AnnotationConfigApplicationContext.<init>(AnnotationConfigApplicationContext.java:84)
    at de.emo.cit.tuberlin.GetController.getUDDISLA(GetController.java:44)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)

当我将fetch＆＃39;类型改为LAZY时，我得到了这个例子：

引起：org.hibernate.LazyInitializationException：懒得初始化角色集合：B.d，无法初始化代理 - 没有会话

有什么想法吗？谢谢; - ）

Answer 1

使用@LazyCollection(LazyCollectionOption.FALSE)可以解决您的问题，请参阅Hibernate cannot simultaneously fetch multiple bags了解详情

无法在org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean同时获取多个行李

1 个答案: