Refactor some lambdas to enable native image building

Without this change a function with a Tomcat wrapper cannot be compiled
to a native image (or it can but it fails at runtime) because there
are lambda$$$ methods in the byte code that refer to missing types.

spring-cloud-function-web/src/main/java/org/springframework/cloud/function/web/function/FunctionEndpointInitializer.java

@@ -108,8 +108,7 @@ class FunctionEndpointInitializer implements ApplicationContextInitializer<Gener
 		context.registerBean(FunctionEndpointFactory.class,
 				() -> new FunctionEndpointFactory(context.getBean(FunctionCatalog.class),
 						context.getBean(RequestProcessor.class), context.getEnvironment()));
-		context.registerBean(RouterFunction.class,
-				() -> context.getBean(FunctionEndpointFactory.class).functionEndpoints());
+		RouterFunctionRegister.register(context);
 	}
 
 	private HttpWebHandlerAdapter httpHandler(GenericApplicationContext context) {
@@ -131,6 +130,15 @@ class FunctionEndpointInitializer implements ApplicationContextInitializer<Gener
 		return handler;
 	}
 
+	private static class RouterFunctionRegister {
+
+		private static void register(GenericApplicationContext context) {
+			context.registerBean(RouterFunction.class,
+					() -> context.getBean(FunctionEndpointFactory.class).functionEndpoints());
+		}
+
+	}
+
 	private static class ServerListener implements SmartApplicationListener {
 
 		private static Log logger = LogFactory.getLog(ServerListener.class);

spring-cloud-function-web/src/main/java/org/springframework/cloud/function/web/source/FunctionExporterInitializer.java

@@ -16,6 +16,8 @@
 
 package org.springframework.cloud.function.web.source;
 
+import java.util.function.Supplier;
+
 import org.springframework.boot.web.reactive.context.ConfigurableReactiveWebEnvironment;
 import org.springframework.boot.web.reactive.context.ReactiveWebApplicationContext;
 import org.springframework.cloud.function.context.FunctionCatalog;
@@ -27,6 +29,7 @@ import org.springframework.util.ClassUtils;
 import org.springframework.web.context.ConfigurableWebEnvironment;
 import org.springframework.web.context.WebApplicationContext;
 import org.springframework.web.reactive.function.client.WebClient;
+import org.springframework.web.reactive.function.client.WebClient.Builder;
 
 /**
  * @author Dave Syer
@@ -49,7 +52,12 @@ class FunctionExporterInitializer implements ApplicationContextInitializer<Gener
 		if (ClassUtils.isPresent("org.springframework.web.reactive.function.client.WebClient",
 				getClass().getClassLoader())) {
 			if (context.getBeanFactory().getBeanNamesForType(WebClient.Builder.class, false, false).length == 0) {
-				context.registerBean(WebClient.Builder.class, () -> WebClient.builder());
+				context.registerBean(WebClient.Builder.class, new Supplier<WebClient.Builder>() {
+					@Override
+					public Builder get() {
+						return WebClient.builder();
+					}
+				});
 			}
 		}
 	}