title: What exactly does Hibernate new_generator_mappings actually do?
body: <p>New to Spring Boot/JPA/Hibernate and I'm trying to understand what the <a href="https://access.redhat.com/documentation/en-US/JBoss_Enterprise_Application_Platform/6.3/html/Migration_Guide/Preserve_the_Existing_Behavior_of_the_Hibernate_Identity_Auto_Generated_Value1.html" rel="noreferrer"><code>hibernate.id.new_generator_mappings</code></a> property <em>actually</em> does.</p>
  
  <p>According to that doc, it:</p>
  
  <blockquote>
    <p>"<em>...directs how identity or sequence columns are generated when using @GeneratedValue</em>"</p>
  </blockquote>
  
  <p>But it doesn't really explain the behavioral difference from when its <code>true</code> vs when its <code>false</code>. Any ideas?</p>