AJ-638: optimize error info for EventHandler constructor check eventSchemes;

Author: chengyitian

src/com/xxdb/streaming/cep/EventHandler.java

@@ -26,9 +26,9 @@ public EventHandler(List<EventScheme> eventSchemes, List<String> eventTimeKeys,
 
         String funcName = "createEventSender";
         // check eventSchemes
-        if (eventSchemes.isEmpty()) {
-            throw new IllegalArgumentException(funcName + " eventSchemes must not be empty");
-        }
+        if (Objects.isNull(eventSchemes) || eventSchemes.isEmpty())
+            throw new IllegalArgumentException("eventSchema must be non-null and non-empty for the EventClient Constructor.");
+
         List<EventScheme> expandEventSchemes = new ArrayList<>(eventSchemes);
         for (EventScheme event : expandEventSchemes) {
             if (Utils.isEmpty(event.getEventType()))