如何访问JPA中的鉴别器列-HowtoaccessdiscriminatorcolumninJPA

2  

If a discriminator column makes sense with InheritanceType.JOINED is worth discussing. I would tend to omit it on joined strategy and only use it with InheritanceType.SINGLE_TABLE.

如果一个鉴别器列对于InheritanceType有意义.JOINED值得讨论。我倾向于在加入策略中省略它,并且只将它与InheritanceType.SINGLE_TABLE一起使用。

Nevertheless, it's possible to map it without duplicate column errors.

不过,可以映射它而不会出现重复的列错误。

If your superclass entity has an inheritance / discriminator definition like:

如果您的超类实体具有继承/鉴别器定义,例如:

@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name = "subtype_id", discriminatorType = DiscriminatorType.INTEGER)

You just have to adjust the mapping to not update the value as usual by setting it readonly:

您只需通过将其设置为readonly来调整映射以不像往常一样更新值:

@Column(name="subtype_id", insertable = false, updatable = false)
protected int subTypeId;

public int getSubTypeId() {
    return subTypeId;
}

Now you can access the discriminator value of the entity.

现在您可以访问实体的鉴别器值。

0  

Same column name is used for relation FK to FeatureSubtype. Use other name for discriminator or don't use discriminator at all.

相同的列名用于FK与FeatureSubtype的关系。使用其他名称作为鉴别器或根本不使用鉴别​​器。

In Hibernate, discriminator column on joined inheritance is supported but not required. Hibernate is querying all subtables to determine correct subclass.

在Hibernate中,支持连接继承的discriminator列,但不是必需的。 Hibernate正在查询所有子表以确定正确的子类。