title: findOne() method is undefined
body: <p>I am new to SpringBoot , and learning about JPA.
  I am trying to create a method to retreive the instance(row) of my Table(entity)
  based on a variable Id(String, primary key) .</p>
  
  <p>I have created an interface TopicRepository extends CrudRepository
  here Topic is my entity class and String is primary key data type(id).</p>
  
  <p>Now while I am following some tutorial , I am trying to retrieve the row based on Id , using the method findOne(id) 
  eg. topicRepository.findOne(id);</p>
  
  <p>but the method is not located or undefined to use.
  Please help me out with this. I am a newbie.
  Thanks in advance.</p>