相关疑难解决方法(0)

我有Hibernate Entities看起来像这样(getters和setter被遗漏):

@Entity
public class EntityA {
    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "parent_id")
    private EntityB parent;
}

@Entity
public class EntityB extends SuperEntity {
    @OneToMany(mappedBy = "parent")
    @Fetch(FetchMode.SUBSELECT)
    @JoinColumn(name = "parent_id")
    private Set<EntityA> children;
}

@MappedSuperclass
public class SuperEntity {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "id")
    private long itemId;
}

当我查询EntityA时,它加载正常,父关联被Hibernate代理替换(因为它是Lazy).如果我想访问父母的id,我执行以下调用:

EntityA entityA = queryForEntityA();
long parentId = entityA.getParent().getItemId();

据我所知,调用不应该向数据库进行往返,因为Id存储在EntityA表中,并且代理应该只返回该值.但是,在我的情况下,这将生成一个SQL语句,该语句提取EntityB,然后才返回Id.

我该如何调查这个问题？导致这种错误行为的可能原因是什么？

我试图坚持我的课程，但它总是引发我这个错误。

这是我的hibernate.cfg.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
  <session-factory>
    <!-- SQL dialect -->
    <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>

    <!-- Database connection settings -->
    <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
    <property name="hibernate.connection.url">jdbc:mysql://localhost:3306/Projecten2?zeroDateTimeBehavior=convertToNull</property>
    <property name="hibernate.connection.username">MyUser</property>
    <property name="hibernate.connection.password">MyPass</property>
    <property name="hibernate.current_session_context_class">org.hibernate.context.ThreadLocalSessionContext</property>

    <!-- Echo all executed SQL to stdout -->
    <property name="show_sql">false</property>

    <!-- Mappings -->
    <mapping class="entity.Presentation"/>
  </session-factory>
</hibernate-configuration>

这是我要坚持的课程

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