Question

我有一个自定义对象：

@Embeddable
public class MyObject () {
    private String field1;
    private String field2;
    //getters and setters...
}

我有一个表示具有两列的表的持久性实体，我将它们称为colA和colB。在持久性实体中，我想将field1映射到colA，将field2映射到colB。我试过了：

@Embedded
@AttributeOverrides({
    @AttributeOverride(name="field1", column = @Column(name="colA", nullable=true)),
    @AttributeOverride(name="field2", column = @Column(name="colB", nullable=true))
})
private MyObject myObject;

但是，如果其中一个字段没有值，则无法持久保存到数据库。我知道JPA 2.1中的AttributeConverter允许我们将对象中的多个字段保存到一列，但有没有办法将对象中的两个字段保存到两个不同的列？

我在运行时遇到的错误：

javax.persistence.PersistenceException：无法构建EntityManagerFactory 在org.hibernate.ejb.Ejb3Configuration.buildEntityManagerFactory（Ejb3Configuration.java:915）引起：org.hibernate.HibernateException：无法实例化默认tuplizer [org.hibernate.tuple.component.PojoComponentTuplizer] 在org.hibernate.tuple.component.ComponentTuplizerFactory.constructTuplizer（ComponentTuplizerFactory.java:101）在org.hibernate.tuple.component.ComponentTuplizerFactory.constructDefaultTuplizer（ComponentTuplizerFactory.java:122）在org.hibernate.tuple.component.ComponentEntityModeToTuplizerMapping。（ComponentEntityModeToTuplizerMapping.java:75）在org.hibernate.tuple.component.ComponentMetamodel。（ComponentMetamodel.java:73）在org.hibernate.mapping.Component.buildType（Component.java:184）在org.hibernate.mapping.Component.getType（Component.java:177）在org.hibernate.tuple.PropertyFactory.buildStandardProperty（PropertyFactory.java:143）在org.hibernate.tuple.component.ComponentMetamodel。（ComponentMetamodel.java:68）在org.hibernate.mapping.Component.buildType（Component.java:184）在org.hibernate.mapping.Component.getType（Component.java:177）在org.hibernate.mapping.SimpleValue.isValid（SimpleValue.java:290）在org.hibernate.mapping.Property.isValid（Property.java:217）在org.hibernate.mapping.PersistentClass.validate（PersistentClass.java:464）在org.hibernate.mapping.RootClass.validate（RootClass.java:235）在org.hibernate.cfg.Configuration.validate（Configuration.java:1362）在org.hibernate.cfg.Configuration.buildSessionFactory（Configuration.java:1865）在org.hibernate.ejb.Ejb3Configuration.buildEntityManagerFactory（Ejb3Configuration.java:906） ......还有4个引起：java.lang.reflect.InvocationTargetException at sun.reflect.NativeConstructorAccessorImpl.newInstance0（Native Method） at sun.reflect.NativeConstructorAccessorImpl.newInstance（NativeConstructorAccessorImpl.java:57） at sun.reflect.DelegatingConstructorAccessorImpl.newInstance（DelegatingConstructorAccessorImpl.java:45） at java.lang.reflect.Constructor.newInstance（Constructor.java:526）在org.hibernate.tuple.component.ComponentTuplizerFactory.constructTuplizer（ComponentTuplizerFactory.java:98） ......还有20个引起：org.hibernate.PropertyNotFoundException：在com.mypackage.persistenceentities.MyEntity上找不到字段[field1] 在org.hibernate.property.DirectPropertyAccessor.getField（DirectPropertyAccessor.java:182）在org.hibernate.property.DirectPropertyAccessor.getField（DirectPropertyAccessor.java:174）在org.hibernate.property.DirectPropertyAccessor.getGetter（DirectPropertyAccessor.java:197）在org.hibernate.mapping.Property.getGetter（Property.java:304）在org.hibernate.tuple.component.PojoComponentTuplizer.buildGetter（PojoComponentTuplizer.java:156）在org.hibernate.tuple.component.AbstractComponentTuplizer。（AbstractComponentTuplizer.java:65）在org.hibernate.tuple.component.PojoComponentTuplizer。（PojoComponentTuplizer.java:60） ......还有25个

谢谢，亚历

如何使用JPA

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