From: Doug Clarke <douglas.clarke_at_oracle.com>
Date: Fri, 1 Sep 2006 12:25:53 -0400

I would create a shared EntityManagerFactory (EMF) and then create an EntityManager (EM) per thread/requests instead of an EMF per thread/request.

Doug
  -----Original Message-----
  From: Daniel Cavalcanti [mailto:dhcavalcanti_at_gmail.com]
  Sent: Friday, September 01, 2006 12:01 PM
  To: persistence_at_glassfish.dev.java.net
  Subject: Re: thread-safety


  Ok,
  thanks,

  So, a solution would be to either serializa access to the method, or the following, right?

  class Foo {

      // method accessed by several concurrent threads
      public void foo() {
          
          EntityManagerFactory emf = Persistence.createEntityManagerFactory("my-persistence-unit");
          EntityManager manager = emf.createEntityManager();

          try {
              manager.getTransaction().begin();
              // TODO: do somethinf
              manager.getTransaction().commit();
          } catch(Exception e) {
              manager.getTransaction().rollback();
          }
         
          manager.close();
          
      }
      
  }


  On 9/1/06, Doug Clarke <douglas.clarke_at_oracle.com> wrote:
    Daniel,

    The specification states in section 5.2:
    "An entity manager may not be shared among multiple concurrently executing threads. Entity managers may only be accessed in a single-threaded manner."

    The underlying TopLink implementation is thread safe but I cannot guarantee the JPA implementation on top of it is as it is not required to be.

    Doug Clarke
    Principal Product Manager
    Oracle TopLink
    douglas.clarke_at_oracle.com
      -----Original Message-----
      From: Daniel Cavalcanti [mailto:dhcavalcanti_at_gmail.com]
      Sent: Friday, September 01, 2006 11:13 AM
      To: persistence_at_glassfish.dev.java.net
      Subject: thread-safety


      Hello,

      Quick question: Is the EntityManager thread safe?

      For example,

      class Foo {

          private EntityManagerFactory emf = Persistence.createEntityManagerFactory("my-persistence-unit");
          private EntityManager manager = emf.createEntityManager();
          
          // method accessed by several concurrent threads
          public void foo() {
              
              try {
                  manager.getTransaction().begin();
                  // TODO: do somethinf
                  manager.getTransaction().commit();
              } catch(Exception e) {
                  manager.getTransaction().rollback();
              }
             
          }
          
      }

      thanks,
      Daniel.