Enable Tomcat, Jetty and Undertow reactive auto-conf

Closes gh-8403

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/webflux/ReactiveWebServerAutoConfiguration.java

@@ -47,7 +47,10 @@ import org.springframework.util.ObjectUtils;
 @ConditionalOnWebApplication(type = ConditionalOnWebApplication.Type.REACTIVE)
 @EnableConfigurationProperties(ServerProperties.class)
 @Import({ReactiveWebServerAutoConfiguration.BeanPostProcessorsRegistrar.class,
-		ReactiveWebServerConfiguration.ReactorNettyAutoConfiguration.class})
+		ReactiveWebServerConfiguration.TomcatAutoConfiguration.class,
+		ReactiveWebServerConfiguration.JettyAutoConfiguration.class,
+		ReactiveWebServerConfiguration.ReactorNettyAutoConfiguration.class,
+		ReactiveWebServerConfiguration.UndertowAutoConfiguration.class})
 public class ReactiveWebServerAutoConfiguration {
 
 	@ConditionalOnMissingBean

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/webflux/ReactiveWebServerConfiguration.java

@@ -16,12 +16,16 @@
 
 package org.springframework.boot.autoconfigure.webflux;
 
+import io.undertow.Undertow;
 import reactor.ipc.netty.http.server.HttpServer;
 
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
 import org.springframework.boot.context.embedded.ReactiveWebServerFactory;
+import org.springframework.boot.context.embedded.jetty.JettyReactiveWebServerFactory;
 import org.springframework.boot.context.embedded.reactor.ReactorNettyReactiveWebServerFactory;
+import org.springframework.boot.context.embedded.tomcat.TomcatReactiveWebServerFactory;
+import org.springframework.boot.context.embedded.undertow.UndertowReactiveWebServerFactory;
 import org.springframework.context.annotation.Bean;
 
 /**
@@ -42,4 +46,32 @@ abstract class ReactiveWebServerConfiguration {
 		}
 	}
 
+	@ConditionalOnMissingBean(ReactiveWebServerFactory.class)
+	@ConditionalOnClass({org.apache.catalina.startup.Tomcat.class})
+	static class TomcatAutoConfiguration {
+		@Bean
+		public TomcatReactiveWebServerFactory tomcatReactiveWebServerFactory() {
+			return new TomcatReactiveWebServerFactory();
+		}
+	}
+
+	@ConditionalOnMissingBean(ReactiveWebServerFactory.class)
+	@ConditionalOnClass({org.eclipse.jetty.server.Server.class})
+	static class JettyAutoConfiguration {
+		@Bean
+		public JettyReactiveWebServerFactory jettyReactiveWebServerFactory() {
+			return new JettyReactiveWebServerFactory();
+		}
+	}
+
+	@ConditionalOnMissingBean(ReactiveWebServerFactory.class)
+	@ConditionalOnClass({Undertow.class})
+	static class UndertowAutoConfiguration {
+		@Bean
+		public UndertowReactiveWebServerFactory undertowReactiveWebServerFactory() {
+			return new UndertowReactiveWebServerFactory();
+		}
+
+	}
+
 }