title: Get lists of ids with JPA instead all Object
body: <p>I am trying to get only the list of ids from a JPA repository.
  Instead of using</p>
  
  <pre><code>List&lt;Case&gt; findAll(Specification&lt;Case&gt; filter);
  </code></pre>
  
  <p>Something like</p>
  
  <pre><code>List&lt;Integer&gt; findAll(Specification&lt;Case&gt; filter);
  </code></pre>
  
  <p>because I don´t need the full object. There is a lot of data on each record, and a lot of records. </p>