You may wish to google for detailed explanation.
A service Locator pattern, suggests you to make a class which is responsible for all the JNDI look-ups of your resources. So, the classes looking for any resource, registered in JNDI, will just call the Service Locator to give that object to it.
A business delegate reduces coupling between presentation-tier clients and business services. It hides the underlying implementation details of the business service, such as lookup (for which it will use Service Locator ) and access details of the
EJB architecture.
Hope this helps !