title: Java Persistence layer in regards to Service/Repository layers
body: <p>I need a solid explanation on three software architecture layers (listed below) in a Java EE environment, that I have taken from multiple contexts.  In short, this is what I have gained:</p>
  
  <ul>
  <li><strong>Service Layer</strong>: Contains services behind the front-end with functionality fit for re-use during the software's life cycle</li>
  <li><strong>Persistence Layer</strong>: Handles operations behind the front-end, intermediate between the front-end and the Repository layer.</li>
  <li><strong>Repository Layer</strong>: Wraps data-handling operations for data creation/retrieval in the back-end.</li>
  </ul>
  
  <p>After panning through multiple articles, I am confused as to where the <em>distinction</em> lies between the Service and Persistence layers - could they overlap or be synonyms of one another?  I never hear them mentioned in really the same context.  </p>
  
  <p>Are all of these layers always used/easily distinguishable?</p>
  
  <p>Thank you.</p>