休眠和通用字段映射 [英] hibernate and generic field mapping
问题描述
我的母类是:
<$>
我想用Hibernate映射一个超类的泛型字段。 p $ p $
@Table(name =ParameterValue)
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name =parameterType ,discriminatorType = DiscriminatorType.STRING)
public abstract class ParameterValue< C>
{
私人C值;
/ *需要帮助* /
public C getValue()
{
返回值;
}
public void setValue(C value)
{
this.value = value;
$ / code $ / pre
$ b $ p一个子类:
@Entity
@DiscriminatorValue(value =integer)
@AttributeOverride(name =value,column = @Column(name =intValue))
public class IntegerParameterValue extends ParameterValue< Integer>
{
}
正如你所看到的,我重写了value字段来指定在数据库中使用哪个列。
我的表ParameterValue由多个列组成,每个类型一个。
CREATE TABLE`ParameterValue`(
`intValue` int(11)DEFAULT NULL,
`doubleValue` double DEFAULT NULL,
`stringValue` text
)ENGINE = InnoDB DEFAULT CHARSET = utf8;
但是hibernate抱怨:
ParameterValue.value具有未绑定类型,并且没有明确的目标实体。解决这个泛型使用问题或者设置一个明确的目标属性(例如@OneToMany(target =)或者使用显式@Type
好吧,但超类中getValue的好配置是什么?(我在HELP NEEDED HERE中发表了评论)
@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)
私人整数intValue;
@Override
public Integer getValue(){
return intValue;
}
@Override
public void setValue(Integer value){
this.intValue = value;
}
}
I want to map a generic field in a superclass with Hibernate.
My mother class is :
@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;
}
}
One subclass :
@Entity
@DiscriminatorValue(value = "integer")
@AttributeOverride(name = "value", column = @Column(name = "intValue"))
public class IntegerParameterValue extends ParameterValue<Integer>
{
}
As you can see I override the value field to specify what column to use in the database. My table ParameterValue is composed of several column, one for each type.
CREATE TABLE `ParameterValue` (
`intValue` int(11) DEFAULT NULL,
`doubleValue` double DEFAULT NULL,
`stringValue` text
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
But hibernate complains that :
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
Ok, but what's the good configuration for getValue in the superclass ? (I've put a comment with "HELP NEEDED HERE")
I'm pretty sure you can't map a single Java attribute to three different columns. You will have to use this:
@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;
}
}
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