Provides to the Data Adapter a special interface for creating ItemEvents
in order to send updates to Lightstreamer Kernel.
If the external feed supplies Item data through old style objects,
like java.util.Hashtable or JMS MapMessage objects, that provide a
java.util.Enumeration to the Fields, then wrapping it into an OldItemEvent
can be simpler than wrapping it into an ItemEvent.
All implementation methods must execute fast and must be nonblocking.
All information needed to extract data must be provided at object
construction. If the implementation were slow, the whole update delivery
process, even for different sessions, would be slowed down.
Returns the value of a named Field (null is a legal value too).
Returns an iterator to browse the names of the supplied Fields,
expressed as String.
If the Item to which this ItemEvent refers has been subscribed
by setting the needsIterator flag as false, the method can return
a null value.
Returns the value of a named Field (null is a legal value too). Returns
null if the Field is not reported in the ItemEvent.
The value can be expressed as either a String or a byte array;
see ItemEvent.getValue(String) for details.
name - A Field name.
a String or a byte array containing the Field value, or null.