mysql - Hibernate allow foreign key to be one of many classes? -

i'm trying implement hashtag functionality in database, allowing me assign hashtag different classes. possible have foreign key inside tags class, 1 of many different classes (article, video, image)? mean having discriminator column.

e.g

@entity @table(name="tags") public class tags {     private string tagname; // hashtag name; e.g cool-photo     private <article, video, photo> relatedobject;      private string type; // can either article, video, photo } 

in example i'd able run simple query:

select t.* tags t type = 'article' , tagname = 'tag-searching-for'  inner join article on t.relatedobject = a.articleid; 

this return bunch of <type-requested> objects type requested (in case, articles)!

is there built in way of doing hibernate or have build own solution (which im happy do, i'd rather check see if theres concret 1 first).

there 2 ways, can use super entity - inheritance.

1. create taggable, new super entity article, video, ...

   @entity public class tag  {     private string tagname; // hashtag name; e.g cool-photo      @manytomany     @jointable(...)     private set<taggable> relatedobjects = new linkedhashset<>();  }  @entity @inheritance(...) public abstract class taggable {     @manytomany(mappedby = "relatedobjects")     protected set<tag> tags = new linkedhashset<>(); }  @entity public class article extends taggable  {     ... } 

2. make tag super entity

   @entity @inheritance(...) public abstract class tag  {     protected string tagname; // hashtag name; e.g cool-photo }  @entity public class articletag extends tag {     @manytomany(mappedby = "tags")     private set<article> articles = new linkedhashset<>(); }  @entity public class article {     @manytomany     @jointable(...)     private set<articletag> tags = new linkedhashset<>(); } 

in both cases query use more (conversely 1 brought in example) [jpql style - not sql!]:

select  article     join a.tags t t.tagname = 'tag-searching-for'  

to articles specific tagname.

imho first 1 requires less refactoring , less boilerplate code, but, due java single-class inheritance limitation, cause problem if/when you'll extend model in future.

as side note, don't see meaning in using single relatedobject, changed set<>