RouterFunctionMapping provides getter for RouterFunction

Issue: SPR-15991

spring-webflux/src/main/java/org/springframework/web/reactive/function/server/support/RouterFunctionMapping.java

@@ -70,6 +70,18 @@ public class RouterFunctionMapping extends AbstractHandlerMapping implements Ini
 	}
 
 
+	/**
+	 * Return the configured {@link RouterFunction}.
+	 * <p><strong>Note:</strong> When router functions are detected from the
+	 * ApplicationContext, this method may return {@code null} if invoked
+	 * prior to {@link #afterPropertiesSet()}.
+	 * @return the router function or {@code null}
+	 */
+	@Nullable
+	public RouterFunction<?> getRouterFunction() {
+		return this.routerFunction;
+	}
+
 	/**
 	 * Configure HTTP message readers to de-serialize the request body with.
 	 * <p>By default this is set to the {@link ServerCodecConfigurer}'s defaults.

spring-webflux/src/test/java/org/springframework/web/reactive/DispatcherHandlerTests.java

@@ -17,18 +17,14 @@ package org.springframework.web.reactive;
 
 import java.nio.charset.StandardCharsets;
 import java.time.Duration;
-import java.util.function.Function;
 import java.util.function.Supplier;
 
 import org.junit.Test;
-import org.mockito.MockSettings;
-import org.mockito.Mockito;
 import reactor.core.publisher.Mono;
 
 import org.springframework.context.support.StaticApplicationContext;
 import org.springframework.core.MethodParameter;
 import org.springframework.core.Ordered;
-import org.springframework.core.codec.CharSequenceEncoder;
 import org.springframework.core.io.buffer.DataBuffer;
 import org.springframework.core.io.buffer.DefaultDataBufferFactory;
 import org.springframework.mock.http.server.reactive.test.MockServerHttpRequest;
@@ -43,7 +39,7 @@ import static org.mockito.Mockito.when;
 import static org.mockito.Mockito.withSettings;
 
 /**
- *
+ * Unit tests for {@link DispatcherHandler}.
  * @author Rossen Stoyanchev
  */
 public class DispatcherHandlerTests {

spring-webmvc/src/main/java/org/springframework/web/servlet/DispatcherServlet.java

@@ -774,13 +774,14 @@ public class DispatcherServlet extends FrameworkServlet {
 	 * Return the configured {@link HandlerMapping} beans that were detected by
 	 * type in the {@link WebApplicationContext} or initialized based on the
 	 * default set of strategies from {@literal DispatcherServlet.properties}.
-	 * @return immutable list with the configured mappings or an empty list
+	 * <p><strong>Note:</strong> This method may return {@code null} if invoked
+	 * prior to {@link #onRefresh(ApplicationContext)}.
+	 * @return immutable list with the configured mappings or {@code null}
 	 * @since 5.0
 	 */
+	@Nullable
 	public List<HandlerMapping> getHandlerMappings() {
-		return this.handlerMappings != null ?
-				Collections.unmodifiableList(this.handlerMappings) :
-				Collections.emptyList();
+		return this.handlerMappings != null ? Collections.unmodifiableList(this.handlerMappings) : null;
 	}
 
 	/**