Question

1.this is how my dao class look like where the transaction code keep repeat for every method. possible to put these snippet code in super class so that i do no need to repeat below code all the time? any elaborate how to do this?

2.if there is a need to put the snippet in super.class. should the super.class be static?

 for (int i = 0; i < NUM_RETRIES; i++) {
     pm.currentTransaction().begin();

     <all my code will be here>

     try {
         pm.currentTransaction().commit();
         break;

     } catch (JDOCanRetryException ex) {
         if (i == (NUM_RETRIES - 1)) { 
             throw ex;
         }
     }
 }

Answer 1

Addressing only the “extract to superclass” issue, you could:

In your base class put:

public abstract Object doTransaction();

public abstract Object executeTransaction(some params){
for (int i = 0; i < NUM_RETRIES; i++) {
     pm.currentTransaction().begin();

     this.doTransaction();

     try {
         pm.currentTransaction().commit();
         break;

     } catch (JDOCanRetryException ex) {
         if (i == (NUM_RETRIES - 1)) { 
             throw ex;
         }
     }
 }
}

In your derived class, redefine doTransaction method

public Object doTransaction() {

 //access database and stuff;
}

Please adjust the return types and parameters accordingly.

Note that there’s nothing static (static methods cant be overridden), its just an implementation of the template method pattern.