Spring Transaction: What will happen if I don't give @Transaction annotation on method
<p>I am using Spring-Boot, Spring Rest Controller and Spring Data JPA. If I don't specify @Transaction then also record get's created but I will like to understand how it happens.My understanding is that Spring by default adds a transaction with default parameters but not sure where it adds is it add Service layer or at Repository.</p>

<pre><code> public interface CustomerRepository extends CrudRepository&lt;Customer, Long&gt; {

    List&lt;Customer&gt; findByLastName(String lastName);
 }

 @Service
 public class CustomerServiceImpl implements CustomerService&gt; {

   List&lt;Customer&gt; findByLastName(String lastName){
     //read operation
    }

 // What will happen if @Transaction is missing. How record get's created without the annotation
  public Customer insert(Customer customer){
  // insert operations
   }
 }
</code></pre>