Refine receive() aop advice and its triggers

* Remove redundant interface for class `CompoundTriggerAdvice`
* Fix potential NPE in `DynamicPeriodicTrigger#nextExecution`
* use if-else in critical path instead of `requireNonNullElse`

Signed-off-by: Jiandong Ma <jiandong.ma.cn@gmail.com>

Author: mjd507

spring-integration-core/src/main/java/org/springframework/integration/aop/CompoundTriggerAdvice.java

@@ -39,8 +39,7 @@
  * @since 4.3
  *
  */
-public class CompoundTriggerAdvice
-		implements MessageSourceMutator, ReceiveMessageAdvice {
+public class CompoundTriggerAdvice implements MessageSourceMutator {
 
 	private final CompoundTrigger compoundTrigger;
 

spring-integration-core/src/main/java/org/springframework/integration/aop/SimpleActiveIdleReceiveMessageAdvice.java

@@ -25,7 +25,7 @@
 import org.springframework.util.Assert;
 
 /**
- A simple advice that polls at one rate when messages exist and another when
+ * A simple advice that polls at one rate when messages exist and another when
  * there are no messages.
  *
  * @author Gary Russell

spring-integration-core/src/main/java/org/springframework/integration/util/CompoundTrigger.java

@@ -23,7 +23,7 @@
 import org.springframework.util.Assert;
 
 /**
- * A {@link Trigger} that delegates the {@link #nextExecutionTime(TriggerContext)}
+ * A {@link Trigger} that delegates the {@link #nextExecution(TriggerContext)}
  * to one of two Triggers. If the {@link #setOverride(Trigger) override} trigger is
  * {@code null}, the primary trigger is invoked; otherwise the override trigger is
  * invoked.

spring-integration-core/src/main/java/org/springframework/integration/util/DynamicPeriodicTrigger.java

@@ -16,6 +16,7 @@
 
 package org.springframework.integration.util;
 
+import java.time.Clock;
 import java.time.Duration;
 import java.time.Instant;
 import java.util.Objects;
@@ -130,14 +131,18 @@ public boolean isFixedRate() {
 	@Override
 	public Instant nextExecution(TriggerContext triggerContext) {
 		Instant lastScheduled = triggerContext.lastScheduledExecution();
+		Clock clock = triggerContext.getClock();
 		if (lastScheduled == null) {
-			return Instant.now().plus(this.initialDuration);
+			return clock.instant().plus(this.initialDuration);
 		}
 		else if (this.fixedRate) {
 			return lastScheduled.plus(this.duration);
 		}
-		return
-				triggerContext.lastCompletion().plus(this.duration); // NOSONAR never null here
+		Instant lastCompletion = triggerContext.lastCompletion();
+		if (lastCompletion == null) {
+			return clock.instant().plus(this.duration);
+		}
+		return lastCompletion.plus(this.duration);
 	}
 
 	@Override