title: Most popular JPA implementation
body: <p>I am a junior programmer and was asked to develop an application that should utilize the Java Persistence API (JPA).</p>
  
  <p>Which is the most popular JPA implementation (Hibernate, Toplink, EclipseLink)</p>
  
  <p>Can I use any of the above with Apache Tomcat or every implementation is tied to a specific server application ?</p>
  
  <p>Are there any good introductory books or tutorials for this subject ?</p>