Add reflection hints for retrieving Undertow's ports

Closes gh-32303

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/embedded/undertow/UndertowWebServer.java

@@ -34,6 +34,8 @@ import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.xnio.channels.BoundChannel;
 
+import org.springframework.aot.hint.RuntimeHints;
+import org.springframework.aot.hint.RuntimeHintsRegistrar;
 import org.springframework.boot.web.server.GracefulShutdownCallback;
 import org.springframework.boot.web.server.GracefulShutdownResult;
 import org.springframework.boot.web.server.PortInUseException;
@@ -401,4 +403,22 @@ public class UndertowWebServer implements WebServer {
 
 	}
 
+	/**
+	 * {@link RuntimeHintsRegistrar} that allows Undertow's configured and actual ports to
+	 * be retrieved at runtime in a native image.
+	 */
+	static class UndertowWebServerRuntimeHints implements RuntimeHintsRegistrar {
+
+		@Override
+		public void registerHints(RuntimeHints hints, ClassLoader classLoader) {
+			hints.reflection().registerTypeIfPresent(classLoader, "io.undertow.Undertow",
+					(hint) -> hint.withField("listeners").withField("channels"));
+			hints.reflection().registerTypeIfPresent(classLoader, "io.undertow.Undertow$ListenerConfig",
+					(hint) -> hint.withField("type").withField("port"));
+			hints.reflection().registerTypeIfPresent(classLoader,
+					"io.undertow.protocols.ssl.UndertowAcceptingSslChannel", (hint) -> hint.withField("ssl"));
+		}
+
+	}
+
 }

spring-boot-project/spring-boot/src/main/resources/META-INF/spring/aot.factories

@@ -6,6 +6,7 @@ org.springframework.boot.env.PropertySourceRuntimeHints,\
 org.springframework.boot.json.JacksonRuntimeHints,\
 org.springframework.boot.logging.java.JavaLoggingSystemRuntimeHints,\
 org.springframework.boot.logging.logback.LogbackRuntimeHints,\
+org.springframework.boot.web.embedded.undertow.UndertowWebServer.UndertowWebServerRuntimeHints,\
 org.springframework.boot.web.server.MimeMappings.MimeMappingsRuntimeHints
 
 org.springframework.beans.factory.aot.BeanFactoryInitializationAotProcessor=\

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/embedded/undertow/UndertowWebServerRuntimeHintsTests.java

@@ -0,0 +1,54 @@
+/*
+ * Copyright 2012-2022 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.web.embedded.undertow;
+
+import io.undertow.Undertow;
+import org.junit.jupiter.api.Test;
+
+import org.springframework.aot.hint.RuntimeHints;
+import org.springframework.aot.hint.predicate.ReflectionHintsPredicates.FieldHintPredicate;
+import org.springframework.aot.hint.predicate.RuntimeHintsPredicates;
+import org.springframework.boot.web.embedded.undertow.UndertowWebServer.UndertowWebServerRuntimeHints;
+import org.springframework.util.ReflectionUtils;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link UndertowWebServerRuntimeHints}.
+ *
+ * @author Andy Wilkinson
+ */
+public class UndertowWebServerRuntimeHintsTests {
+
+	@Test
+	void registersHints() throws ClassNotFoundException {
+		RuntimeHints runtimeHints = new RuntimeHints();
+		new UndertowWebServerRuntimeHints().registerHints(runtimeHints, getClass().getClassLoader());
+		assertThat(RuntimeHintsPredicates.reflection().onField(Undertow.class, "listeners")).accepts(runtimeHints);
+		assertThat(RuntimeHintsPredicates.reflection().onField(Undertow.class, "channels")).accepts(runtimeHints);
+		assertThat(reflectionOnField("io.undertow.Undertow$ListenerConfig", "type")).accepts(runtimeHints);
+		assertThat(reflectionOnField("io.undertow.Undertow$ListenerConfig", "port")).accepts(runtimeHints);
+		assertThat(reflectionOnField("io.undertow.protocols.ssl.UndertowAcceptingSslChannel", "ssl"))
+				.accepts(runtimeHints);
+	}
+
+	private FieldHintPredicate reflectionOnField(String className, String fieldName) throws ClassNotFoundException {
+		return RuntimeHintsPredicates.reflection()
+				.onField(ReflectionUtils.findField(Class.forName(className), fieldName));
+	}
+
+}