I was thinking to switch to OpenJPA from Spring JDBC, just recently run
a very simple test with 2 classes, SQL insert basically, the difference
between plain JDBC and OpenJPA is more than 7 times!
Why such poor performance? Below is my sample code and results, I used
Enhancer as JVM argument, actually without it JPA result was almost
twice faster!

public static void main(String[] args) {
   
   
    Bill bill = new Bill();
    int id = new JVMRandom().nextInt(Integer.MAX_VALUE);
    bill.setId(id);
    bill.setCreated(new Date());
    bill.setPurchaseid(501253634);
    bill.setStatus(1);

    // System.out.println("bill id=" + id);

    Product prod = new Product();
    prod.setId(1);

    BillProduct bp = new BillProduct();
    bp.setBillid(bill);
    bp.setId(new JVMRandom().nextInt(Integer.MAX_VALUE));
    bp.setProductid(prod);    
   
    StopWatch sw = new StopWatch();    
   

    try {
       Class.forName("org.postgresql.Driver");

       String url =
"jdbc:postgresql://localhost/mydb?user=admin&password=admin";
       Connection conn = DriverManager.getConnection(url);
       conn.setAutoCommit(false);
     
       // System.out.println("bill id=" + id);
       sw.start();

       PreparedStatement pstm = conn
            .prepareStatement("insert into bill(id, status,
purchaseid, created) values (?, ?, ?, ?)");
       pstm.setInt(1, bill.getId());
       pstm.setInt(2, bill.getStatus());
       pstm.setInt(3, 501253634);
       pstm.setDate(4, new java.sql.Date(System.currentTimeMillis()));
       pstm.executeUpdate();
       pstm.close();

       pstm = conn
            .prepareStatement("insert into bill_product(id,
productid, billid) values (?, ?, ?)");
       pstm.setInt(1, new JVMRandom().nextInt(Integer.MAX_VALUE));
       pstm.setInt(2, 1);
       pstm.setInt(3, bill.getId());
       pstm.executeUpdate();
       pstm.close();

       conn.commit();
       sw.stop();

       System.out.println("jdbc time=" + sw.getTime());
       conn.close();

    } catch (Exception e) {
       // TODO Auto-generated catch block
       e.printStackTrace();
    }
   
    sw.reset();

   
    //openjpa
    id = new JVMRandom().nextInt(Integer.MAX_VALUE);
    bill.setId(id);
    bp.setId(new JVMRandom().nextInt(Integer.MAX_VALUE));

    // persist
    EntityManagerFactory emf = Persistence
          .createEntityManagerFactory("testjpa");
    EntityManager em = emf.createEntityManager();

    sw.start();

    em.getTransaction().begin();

    em.persist(bill);
    em.flush();
    em.persist(bp);

    em.getTransaction().commit();

    sw.stop();
    System.out.println("openjpa time=" + sw.getTime());  

 
    em.close();

  }



*Console output: *

jdbc time=78
93 testjpa INFO  [main] openjpa.Runtime - Starting OpenJPA 1.2.0
203 testjpa INFO  [main] openjpa.jdbc.JDBC - Using dictionary class
"org.apache.openjpa.jdbc.sql.PostgresDictionary".
openjpa time=547