Sonar fixes

* exposing internal objects
* boolean complexity
* names, methods with _
* missing `default` in switch
* lost stack trace
* unnecessary null check before instanceof
* unused parameter

* Fix method name

spring-integration-test-support/src/main/java/org/springframework/integration/test/util/OnlyOnceTrigger.java

@@ -54,7 +54,7 @@ public class OnlyOnceTrigger implements Trigger {
 			return null;
 		}
 
-		return this.executionTime;
+		return this.executionTime; // NOSONAR - expose internals
 	}
 
 	@Override