休眠和通用字段映射

Question

我想用Hibernate映射超类中的泛型字段.

我的母班是:

@Entity
@Table(name = "ParameterValue")
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name = "parameterType", discriminatorType = DiscriminatorType.STRING)
public abstract class ParameterValue<C>
{
    private C value;

    /* HELP NEEDED HERE */
    public C getValue()
    {
        return value;
    }

    public void setValue(C value)
    {
        this.value = value;
    }
}

一个子类:

@Entity
@DiscriminatorValue(value = "integer")
@AttributeOverride(name = "value", column = @Column(name = "intValue"))
public class IntegerParameterValue extends ParameterValue<Integer>
{
}

如您所见,我重写值字段以指定在数据库中使用的列.我的表ParameterValue由几列组成,每种类型一列.

CREATE TABLE `ParameterValue` (
    `intValue` int(11) DEFAULT NULL,
    `doubleValue` double DEFAULT NULL,
    `stringValue` text
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

但是hibernate抱怨说:

ParameterValue.value has an unbound type and no explicit target entity. Resolve this Generic usage issue or set an explicit target attribute (eg @OneToMany(target=) or use an explicit @Type

好的,但是超类中getValue的良好配置是什么？(我已经发表评论"需要帮助")

Answer 1

我很确定你不能将一个Java属性映射到三个不同的列.你将不得不使用这个:

@Entity
@Table(name = "ParameterValue")
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name = "parameterType", discriminatorType = DiscriminatorType.STRING)
public abstract class ParameterValue<C> {
    public abstract C getValue();

    public abstract void setValue(C value);
}

@Entity
@DiscriminatorValue(value = "integer")
public class IntegerParameterValue extends ParameterValue<Integer> {
    @Column(name = "intValue")
    private Integer intValue;

    @Override
    public Integer getValue() {
        return intValue;
    }

    @Override
    public void setValue(Integer value) {
        this.intValue = value;
    }
}