Explicit note on scheduled methods with a return value

Issue: SPR-14195

spring-context/src/main/java/org/springframework/scheduling/annotation/Scheduled.java

@@ -24,12 +24,13 @@ import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
 
 /**
- * Annotation that marks a method to be scheduled. Exactly one of the
+ * An annotation that marks a method to be scheduled. Exactly one of
- * {@link #cron()}, {@link #fixedDelay()}, or {@link #fixedRate()}
+ * the {@link #cron()}, {@link #fixedDelay()}, or {@link #fixedRate()}
  * attributes must be specified.
  *
- * <p>The annotated method must expect no arguments and have a
+ * <p>The annotated method must expect no arguments. It will typically have
- * {@code void} return type.
+ * a {@code void} return type; if not, the returned value will be ignored
+ * when called through the scheduler.
  *
  * <p>Processing of {@code @Scheduled} annotations is performed by
  * registering a {@link ScheduledAnnotationBeanPostProcessor}. This can be

spring-context/src/main/resources/org/springframework/scheduling/config/spring-task-4.3.xsd

@@ -293,7 +293,9 @@
 		<xsd:attribute name="method" type="xsd:string" use="required">
 			<xsd:annotation>
 				<xsd:documentation><![CDATA[
-	The name of the method to be invoked.
+	The name of the method to be invoked. The target method must expect no arguments.
+	It will typically have a void return type; if not, the returned value will be
+	ignored when called through the scheduler.
 				]]></xsd:documentation>
 				<xsd:appinfo>
 					<tool:annotation>