Hi, I'm new to hibernate, so sorry for silly question. I have many-to-many mapping (Teacher to Languages they know). What I want to do is to avoid redundancy. So how to tell Hibernate when adding to "languages" table, that he should add language only and only if LANGUAGE_NAME is not repeated? Otherwise just add record in "middle" table (It do so, but also redundantly adds same language). I think that using equals would do the job but on the other hand that would be inefficient because he need to download all content from certain table (to run java method).
I have following class

The most natural approach to solve this, is to declare language name as @NaturalId



Then in your business code, you can check the existance of a language by:

Language lang = (Language) session.bySimpleNaturalId(Language.class).load(newlanguage);
if (lang == null) { // create the new language only if it does not exist yet
lang = new Language(newlanguage);
session.save(lang);
}

Furthermore the @NaturalId declaration has as conseguence that an unique index will be defined on column LANGUAGE_NAME when
you generate the schema. This avoids duplicate entries a priori.