2.9. Value List Handler

The Value List Handler uses the GoF iterator pattern to provide query execution and processing services. The Value List Handler caches the results of the query execution and return subsets of the result to the clients as requested. By using this pattern, it is possible to avoid overheads associated with finding large numbers of entity beans. The Value List Handler uses a Data Access Object to execute a query and fetch the results from a persistent store. The Value List Handler pattern caches results and allows the client to traverse and select from the results. 

UML representation


The following lists the benefits of using the Value List Handler pattern:
  • Caches search results
  • Improves network performance
  • Improves separation of concerns

When to Use

You should use the Value List Handler pattern when you:
  • Want to iterate through a set of objects.
  • Implement read-only lists without transactions.