Hi Rajith, I have a few comments on the patch:
The broker does not currently depend on the JMS specification jar, so it cant use the javax.jms.DeliveryMode constants; there are a matching set of constants in the BasicContentHeaderProperties class, if not others.
The [pre-existing] log statements will now continue to output the int value for the DeliveryMode whilst the return value is updated to be a String, I think it should probably log the String now, or both.
There should be a constant (one may or may not exist in the code base) for the PERSISTENT and NON_PERSISTENT strings instead of sprinkling more literals around the code base for them.
The patch introduces a number of tabs instead of using spaces.