Question

我有3个表的遗留数据库：ENTITY1，ENTITY2，PROPERTY。每个实体都有几个属性。两个实体表都通过entity_id键与属性表绑定，该键位于属性表中。所以我没有真正的限制。

DB方案：

我更喜欢将所有属性存储在Entity1-class中的Map中，因此我必须在Property-class中进行多对一的关联（我还没有建立其他解决方案。它们是否存在？）。

那么如何将Entity2-class与属性类相关联？

Enity1.class：

@Entity
@Table(name = "ENTITY1")
public class Entity1 {

    @Id
    @Column(name = "ENTITY_ID")
    private long id;

    @Column(name = "some_field")
    private String field;

    @OneToMany(mappedBy = "entityId")
    @MapKey(name="key")
    private Map<Long, Property> properties;
}

Property.class

    @Entity
    @Table(name = "PROPERTY")
    public class Property {

        @Id
        @Column(name = "property_id")
        private long id;

        @Column
        private long key;

        @Column
        private String value;

//are there other solutions?
        @ManyToOne
        @JoinColumn(name = "ENTITY_ID", referencedColumnName = "ENTITY_ID")
        private Entity1 entity1;
    }

Entity2.class skeleton

@Entity
@Table(name = "ENTITY1")
public class Entity2 {

    @Id
    @Column(name = "ENTITY_ID")
    private long id;

    @Column(name = "some_field")
    private String field;

    // What can I do?
    private Map<Long, Property> properties;
}

无法从下一个例外的Property.class中删除@ManuToOne annoutation：

11:38:40,825 ERROR [org.jboss.msc.service.fail] (ServerService Thread Pool -- 72) MSC000001: Failed to start service jboss.persistenceunit."sudir-gateway-ear-0.0.1-SNAPSHOT.ear#primary": org.jboss.msc.service.StartException in service jboss.persistenceunit."sudir-gateway-ear-0.0.1-SNAPSHOT.ear#primary": java.lang.NullPointerException
       at org.jboss.as.jpa.service.PersistenceUnitServiceImpl$1$1.run(PersistenceUnitServiceImpl.java:172) [wildfly-jpa-8.2.0.Final.jar:8.2.0.Final]
       at org.jboss.as.jpa.service.PersistenceUnitServiceImpl$1$1.run(PersistenceUnitServiceImpl.java:117) [wildfly-jpa-8.2.0.Final.jar:8.2.0.Final]
       at java.security.AccessController.doPrivileged(Native Method) [rt.jar:1.7.0_51]
       at org.wildfly.security.manager.WildFlySecurityManager.doChecked(WildFlySecurityManager.java:474)
       at org.jboss.as.jpa.service.PersistenceUnitServiceImpl$1.run(PersistenceUnitServiceImpl.java:182) [wildfly-jpa-8.2.0.Final.jar:8.2.0.Final]
       at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145) [rt.jar:1.7.0_51]
       at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) [rt.jar:1.7.0_51]
       at java.lang.Thread.run(Thread.java:744) [rt.jar:1.7.0_51]
       at org.jboss.threads.JBossThread.run(JBossThread.java:122)
Caused by: java.lang.NullPointerException
       at org.hibernate.cfg.annotations.CollectionBinder.bindCollectionSecondPass(CollectionBinder.java:1460) [hibernate-core-4.3.7.Final.jar:4.3.7.Final]
       at org.hibernate.cfg.annotations.CollectionBinder.bindOneToManySecondPass(CollectionBinder.java:864) [hibernate-core-4.3.7.Final.jar:4.3.7.Final]
       at org.hibernate.cfg.annotations.CollectionBinder.bindStarToManySecondPass(CollectionBinder.java:779) [hibernate-core-4.3.7.Final.jar:4.3.7.Final]
       at org.hibernate.cfg.annotations.MapBinder$1.secondPass(MapBinder.java:107) [hibernate-core-4.3.7.Final.jar:4.3.7.Final]
       at org.hibernate.cfg.CollectionSecondPass.doSecondPass(CollectionSecondPass.java:70) [hibernate-core-4.3.7.Final.jar:4.3.7.Final]
       at org.hibernate.cfg.Configuration.originalSecondPassCompile(Configuration.java:1697) [hibernate-core-4.3.7.Final.jar:4.3.7.Final]
       at org.hibernate.cfg.Configuration.secondPassCompile(Configuration.java:1426) [hibernate-core-4.3.7.Final.jar:4.3.7.Final]
       at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1846) [hibernate-core-4.3.7.Final.jar:4.3.7.Final]
       at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl$4.perform(EntityManagerFactoryBuilderImpl.java:852) [hibernate-entitymanager-4.3.7.Final.jar:4.3.7.Final]
       at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl$4.perform(EntityManagerFactoryBuilderImpl.java:845) [hibernate-entitymanager-4.3.7.Final.jar:4.3.7.Final]
       at org.hibernate.boot.registry.classloading.internal.ClassLoaderServiceImpl.withTccl(ClassLoaderServiceImpl.java:398) [hibernate-core-4.3.7.Final.jar:4.3.7.Final]
       at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:844) [hibernate-entitymanager-4.3.7.Final.jar:4.3.7.Final]
       at org.jboss.as.jpa.hibernate4.TwoPhaseBootstrapImpl.build(TwoPhaseBootstrapImpl.java:44) [jipijapa-hibernate4-3-1.0.1.Final.jar:]
       at org.jboss.as.jpa.service.PersistenceUnitServiceImpl$1$1.run(PersistenceUnitServiceImpl.java:154) [wildfly-jpa-8.2.0.Final.jar:8.2.0.Final]
       ... 8 more

Answer 1

您不需要ManyToOne。您只需要在OneToMany关联上指定JoinColumn批注：

@OneToMany
@JoinColumn(name = "entity_id")
private Map<Long, Property> properties;

AFAIK，在第二个实体上做同样的事情应该可以正常工作。我想你知道，只要Enity1与Entity2具有相同的ID，这个设计就会崩溃。

休眠。将两个表与逐个关键列

1 个答案: