Polish contribution

Closes spring-projectsgh-6666

Author: snicoll

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/amqp/RabbitProperties.java

@@ -504,7 +504,7 @@ public static class Listener {
 		private Boolean defaultRequeueRejected;
 
 		/**
-		 * How often to publish idle container events.
+		 * How often idle container events should be published in milliseconds.
 		 */
 		private Long idleEventInterval;
 
@@ -571,7 +571,7 @@ public void setDefaultRequeueRejected(Boolean defaultRequeueRejected) {
 		}
 
 		public Long getIdleEventInterval() {
-			return idleEventInterval;
+			return this.idleEventInterval;
 		}
 
 		public void setIdleEventInterval(Long idleEventInterval) {

spring-boot-docs/src/main/asciidoc/appendix-application-properties.adoc

@@ -863,6 +863,7 @@ content into your application; rather pick only the properties that you need.
 	spring.rabbitmq.listener.auto-startup=true # Start the container automatically on startup.
 	spring.rabbitmq.listener.concurrency= # Minimum number of consumers.
 	spring.rabbitmq.listener.default-requeue-rejected= # Whether or not to requeue delivery failures; default `true`.
+	spring.rabbitmq.idle-event-interval= # How often idle container events should be published in milliseconds.
 	spring.rabbitmq.listener.max-concurrency= # Maximum number of consumers.
 	spring.rabbitmq.listener.prefetch= # Number of messages to be handled in a single request. It should be greater than or equal to the transaction size (if used).
 	spring.rabbitmq.listener.retry.enabled=false # Whether or not publishing retries are enabled.