title: How to get the primary key of any JPA entity?
body: <p>For every @Entity I need to perform the following:</p>
  
  <pre><code>public &lt;Entity&gt; boolean insert(final Entity entity){
      if (em.find(entity.getClass(), entity.getId()) == null) {
          et.begin();
          em.persist(entity);
          et.commit();
          return true;
      }
      return false;
  }
  </code></pre>
  
  <p>That is persist the entity if it didn't exist, and know if it did or not exist.
  With Entity I'm trying to reach @Entity, although I realize it's not an inheritance relationship.
  What class can I use to refer to every JPA entity? I could just create an interface/abstract class MyEntities and have all of them inherit, but is that the way?
  I'm hoping for less code. Also, I'd expect to be able to extract the primary key of every entity, as I attempt in .getId().</p>