Add native support for RSocketExchange.

This commit introduces new AOT processors that look for
`@RSocketExchange` annotated methods on interfaces implemented by beans
and registers reachability metadata accordingly:

* JDK proxies for the beans themselves
* invocation reflection for annotated methods
* binding reflection for arguments and return types

This allows to compile such clients to Native Images.

Closes gh-29877

spring-messaging/src/main/java/org/springframework/messaging/rsocket/service/RSocketExchange.java

@@ -22,6 +22,8 @@ import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
 
+import org.springframework.aot.hint.annotation.Reflective;
+
 /**
  * Annotation to declare a method on an RSocket service interface as an RSocket
  * endpoint. The endpoint route is determined through the annotation attribute,
@@ -65,6 +67,7 @@ import java.lang.annotation.Target;
 @Target({ElementType.TYPE, ElementType.METHOD})
 @Retention(RetentionPolicy.RUNTIME)
 @Documented
+@Reflective(RSocketExchangeReflectiveProcessor.class)
 public @interface RSocketExchange {
 
 	/**

spring-messaging/src/main/java/org/springframework/messaging/rsocket/service/RSocketExchangeBeanRegistrationAotProcessor.java

@@ -0,0 +1,84 @@
+/*
+ * Copyright 2002-2023 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.messaging.rsocket.service;
+
+import java.util.HashSet;
+import java.util.Set;
+
+import org.springframework.aop.framework.AopProxyUtils;
+import org.springframework.aot.generate.GenerationContext;
+import org.springframework.aot.hint.ProxyHints;
+import org.springframework.beans.factory.aot.BeanRegistrationAotContribution;
+import org.springframework.beans.factory.aot.BeanRegistrationAotProcessor;
+import org.springframework.beans.factory.aot.BeanRegistrationCode;
+import org.springframework.beans.factory.support.RegisteredBean;
+import org.springframework.core.annotation.MergedAnnotations;
+import org.springframework.util.ClassUtils;
+import org.springframework.util.ReflectionUtils;
+
+/**
+ * An AOT {@link BeanRegistrationAotProcessor} that detects the presence of
+ * {@link RSocketExchange @RSocketExchange} on methods and creates
+ * the required proxy hints.
+ * Based on {@code HttpExchangeBeanRegistrationAotProcessor}
+ *
+ * @author Sebastien Deleuze
+ * @author Olga Maciaszek-Sharma
+ * @since 6.0
+ * @see org.springframework.web.service.annotation.HttpExchangeBeanRegistrationAotProcessor
+ */
+class RSocketExchangeBeanRegistrationAotProcessor implements BeanRegistrationAotProcessor {
+
+	@Override
+	public BeanRegistrationAotContribution processAheadOfTime(RegisteredBean registeredBean) {
+		Class<?> beanClass = registeredBean.getBeanClass();
+		Set<Class<?>> exchangeInterfaces = new HashSet<>();
+		for (Class<?> interfaceClass : ClassUtils.getAllInterfacesForClass(beanClass)) {
+			ReflectionUtils.doWithMethods(interfaceClass, method -> {
+				if (!exchangeInterfaces.contains(interfaceClass) &&
+						MergedAnnotations.from(method, MergedAnnotations.SearchStrategy.TYPE_HIERARCHY)
+								.get(RSocketExchange.class).isPresent()) {
+					exchangeInterfaces.add(interfaceClass);
+				}
+			});
+		}
+		if (!exchangeInterfaces.isEmpty()) {
+			return new RSocketExchangeBeanRegistrationContribution(exchangeInterfaces);
+		}
+		return null;
+	}
+
+	private static class RSocketExchangeBeanRegistrationContribution implements BeanRegistrationAotContribution {
+
+		private final Set<Class<?>> rSocketExchangeInterfaces;
+
+		public RSocketExchangeBeanRegistrationContribution(Set<Class<?>> rSocketExchangeInterfaces) {
+			this.rSocketExchangeInterfaces = rSocketExchangeInterfaces;
+		}
+
+		@Override
+		public void applyTo(GenerationContext generationContext,
+				BeanRegistrationCode beanRegistrationCode) {
+			ProxyHints proxyHints = generationContext.getRuntimeHints().proxies();
+			for (Class<?> httpExchangeInterface : this.rSocketExchangeInterfaces) {
+				proxyHints.registerJdkProxy(AopProxyUtils
+						.completeJdkProxyInterfaces(httpExchangeInterface));
+			}
+		}
+
+	}
+}

spring-messaging/src/main/java/org/springframework/messaging/rsocket/service/RSocketExchangeReflectiveProcessor.java

@@ -0,0 +1,68 @@
+/*
+ * Copyright 2002-2023 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.messaging.rsocket.service;
+
+import java.lang.reflect.AnnotatedElement;
+import java.lang.reflect.Method;
+import java.lang.reflect.Parameter;
+
+import org.springframework.aot.hint.BindingReflectionHintsRegistrar;
+import org.springframework.aot.hint.ExecutableMode;
+import org.springframework.aot.hint.ReflectionHints;
+import org.springframework.aot.hint.annotation.ReflectiveProcessor;
+import org.springframework.core.MethodParameter;
+
+/**
+ * A {@link ReflectiveProcessor} implementation for {@link RSocketExchange @RSocketExchange}
+ * annotated methods. In addition to registering reflection hints for invoking
+ * the annotated method, this implementation handles reflection-based
+ * binding for return types and parameters.
+ * Based on {@code HttpExchangeReflectiveProcessor}.
+ *
+ * @author Sebastien Deleuze
+ * @author Olga Maciaszek-Sharma
+ * @since 6.0
+ * @see org.springframework.web.service.annotation.HttpExchangeReflectiveProcessor
+ */
+public class RSocketExchangeReflectiveProcessor implements ReflectiveProcessor {
+
+	private final BindingReflectionHintsRegistrar bindingRegistrar = new BindingReflectionHintsRegistrar();
+
+	@Override
+	public void registerReflectionHints(ReflectionHints hints, AnnotatedElement element) {
+		if (element instanceof Method method) {
+			this.registerMethodHints(hints, method);
+		}
+	}
+
+	protected void registerMethodHints(ReflectionHints hints, Method method) {
+		hints.registerMethod(method, ExecutableMode.INVOKE);
+		for (Parameter parameter : method.getParameters()) {
+			// Also register non-annotated parameters to handle metadata
+			this.bindingRegistrar.registerReflectionHints(hints,
+					MethodParameter.forParameter(parameter).getGenericParameterType());
+		}
+		registerReturnTypeHints(hints, MethodParameter.forExecutable(method, -1));
+	}
+
+	protected void registerReturnTypeHints(ReflectionHints hints, MethodParameter returnTypeParameter) {
+		if (!void.class.equals(returnTypeParameter.getParameterType())) {
+			this.bindingRegistrar.registerReflectionHints(hints, returnTypeParameter
+					.getGenericParameterType());
+		}
+	}
+}

spring-messaging/src/main/resources/META-INF/spring/aot.factories

@@ -0,0 +1,2 @@
+org.springframework.beans.factory.aot.BeanRegistrationAotProcessor=\
+org.springframework.messaging.rsocket.service.RSocketExchangeBeanRegistrationAotProcessor