How to map one-to-many collection with join table using discriminator

I'm trying to implement a basic tagging system with hibernate. The problem is that everyone has been subclassing Tag to make the mapping easier. I want to keep my Tag object agnostic to how it's used. It should never be specific to a type. However, the mapping has proven to be very difficult. Here is what I am trying to accomplish.

I am starting out with two classes Tag and Prefix. Prefix will contain a collection of tags. I have 3 tables. prefix, tags and tagged where tagged is a table joining prefix and tags. The enumeration lists the other objects 开发者_运维技巧that I will tag. This is how I want to support different types.

It looks like this:

CREATE TABLE tagged(
tag_id INT(11) NOT NULL,
object_id INT(11) NOT NULL,
discriminator ENUM('PREFIX', 'ROOT', 'SUFFIX') 
) ENGINE=INNODB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;

At the heart of my mapping I have a one-to-many mapping

@OneToMany
@JoinTable(name = "tagged", joinColumns = { @JoinColumn(name = "object_id") }, inverseJoinColumns = @JoinColumn(name = "id"))
public List<Tag> getTags() {
    return tags;
}

So, the question is, how do I join to the discriminator table and set a value for it? I initially tried:

@OneToMany
@JoinTable(name = "tagged", joinColumns = @JoinColumn(name = "object_id"), inverseJoinColumns = @JoinColumn(name = "id"))
@Where(clause = "discriminator='PREFIX'")
public List<Tag> getTags() {
    return tags;
}

This didn't work. Hibernate was looking in the tags table for the discriminator. Any ideas? Thanks!

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Have you tried using the WhereJoinTable annotation? Given its documentation, it should do what you want.