Edit Javadoc in MessageRoutingFunction and RoutingFunction

Refine implementation of RoutingFunction

Closes #1216

spring-cloud-function-context/src/main/java/org/springframework/cloud/function/context/MessageRoutingCallback.java

@@ -21,21 +21,22 @@ import org.springframework.messaging.Message;
 
 /**
  * Java-based strategy to assist with determining the name of the route-to function definition.
- * Once implementation is registered as a bean in application context
+ * Once an implementation is registered as a bean in application context
  * it will be picked up by the {@link RoutingFunction}.
- *
+ * <p/>
  * While {@link RoutingFunction} provides several mechanisms to determine the route-to function definition
  * this callback takes precedence over all of them.
  *
  * @author Oleg Zhurakousky
+ * @author John Blum
  * @since 3.1
  */
 public interface MessageRoutingCallback {
 
 	/**
-	 * Computes and returns the instance of {@link String} which encapsulates,
-	 * at the very minimum, function definition.
-	 * <br><br>
+	 * Computes and returns an instance of {@link String}, which encapsulates,
+	 * at the very minimum, a function definition.
+	 * <p/>
 	 * Providing such message is primarily an optimization feature. It could be useful for cases
 	 * where routing procedure is complex and results in, let's say, conversion of the payload to
 	 * the target type, which would effectively be thrown away if the ability to modify the target

spring-cloud-function-context/src/main/java/org/springframework/cloud/function/context/config/RoutingFunction.java

@@ -45,10 +45,11 @@ import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
 
 /**
- * An implementation of Function which acts as a gateway/router by actually
+ * An implementation of {@link Function} which acts as a gateway/router by actually
  * delegating incoming invocation to a function specified .. .
  *
  * @author Oleg Zhurakousky
+ * @author John Blum
  * @since 2.1
  *
  */
@@ -127,8 +128,7 @@ public class RoutingFunction implements Function<Object, Object> {
 	private Object route(Object input, boolean originalInputIsPublisher) {
 		FunctionInvocationWrapper function = null;
 
-		if (input instanceof Message) {
-			Message<?> message = (Message<?>) input;
+		if (input instanceof Message<?> message) {
 			if (this.routingCallback != null) {
 				String functionDefinition = this.routingCallback.routingResult(message);
 				if (StringUtils.hasText(functionDefinition)) {
@@ -155,7 +155,7 @@ public class RoutingFunction implements Function<Object, Object> {
 				}
 			}
 		}
-		else if (input instanceof Publisher) {
+		else if (input instanceof Publisher<?> publisher) {
 			if (StringUtils.hasText(functionProperties.getDefinition())) {
 				function = functionFromDefinition(functionProperties.getDefinition());
 			}
@@ -163,9 +163,9 @@ public class RoutingFunction implements Function<Object, Object> {
 				function = this.functionFromExpression(functionProperties.getRoutingExpression(), input);
 			}
 			else {
-				return input instanceof Mono
-							? Mono.from((Publisher<?>) input).map(v -> route(v, originalInputIsPublisher))
-									: Flux.from((Publisher<?>) input).map(v -> route(v, originalInputIsPublisher));
+				return input instanceof Mono<?> mono
+							? Mono.from(mono).map(v -> route(v, originalInputIsPublisher))
+									: Flux.from(publisher).map(v -> route(v, originalInputIsPublisher));
 			}
 		}
 		else {
@@ -184,7 +184,7 @@ public class RoutingFunction implements Function<Object, Object> {
 			}
 		}
 
-		if (function.getTarget().equals(this)) {
+		if (this.equals(function.getTarget())) {
 			throw new IllegalStateException("Failed to establish route, and routing to itself is not allowed as it creates a loop. Please provide: "
 					+ "'spring.cloud.function.definition' as Message header or as application property or "
 					+ "'spring.cloud.function.routing-expression' as application property.");