使用JPA 1.0持久化Map的@ElementCollection的替代方法 <String,String> ？

Question

I'm trying to persist a simple Map of attributes as a key value pair for one of my persisted objects. I found a good guide on this matter here . But it only shows how to map when the value of the key is a mapped object (with a 'mapped by' property). My scenario is simpler than this. All I need is to persist a Map<String, String> for a key value pair. I found that I could use @ElementCollection but it is only supported on JPA 2 (the platform I'm working on is still on JPA1).

This is how my code looks like so far:

@Entity
public class MyClass {

    private Map<String, String> attributes;

    @OneToMany
    @MapKey(name="key")
    @JoinTable(name="MyClass_attributes")
    public Map<String, String> getAttributes () {
        return this.attributes;
    }

    public void setAttributes(Map<String, String> attributes) {
        this.attributes = attributes;
    }

}

But I'm getting this error:

Caused by: org.hibernate.AnnotationException: 
Use of @OneToMany or @ManyToMany targeting 
an unmapped class: mypackage.MyClass.attributes[java.lang.String]

Answer 1

Try to create a class for the map's value, like TargetClass. Then the map would be this:

private Map<String, TargetClass> attributes;

In this case the JoinTable doesn't need.