Add Reactor classpath checks in argument resolvers

HTTP interface client argument resolvers for RequestBody and
RequestPart now handle reactive input conditionally.

See gh-30117

spring-web/src/main/java/org/springframework/web/service/invoker/HttpExchangeAdapter.java

@@ -22,8 +22,10 @@ import org.springframework.http.ResponseEntity;
 import org.springframework.lang.Nullable;
 
 /**
- * Contract to abstract an underlying HTTP client and decouple it from the
- * {@linkplain HttpServiceProxyFactory#createClient(Class) HTTP service proxy}.
+ * Contract to abstract an HTTP client from {@linkplain HttpServiceProxyFactory}
+ * and make it pluggable.
+ *
+ * <p>For reactive clients, see {@link ReactorHttpExchangeAdapter}.
  *
  * @author Rossen Stoyanchev
  * @since 6.1

spring-web/src/main/java/org/springframework/web/service/invoker/HttpRequestValues.java

@@ -43,7 +43,7 @@ import org.springframework.web.util.UriUtils;
  * Container for HTTP request values extracted from an
  * {@link org.springframework.web.service.annotation.HttpExchange @HttpExchange}-annotated
  * method and argument values passed to it. This is then given to
- * {@link HttpClientAdapter} to adapt to the underlying HTTP client.
+ * {@link HttpExchangeAdapter} to adapt to the underlying HTTP client.
  *
  * @author Rossen Stoyanchev
  * @since 6.0

spring-web/src/main/java/org/springframework/web/service/invoker/HttpServiceProxyFactory.java

@@ -53,6 +53,7 @@ import org.springframework.web.service.annotation.HttpExchange;
  *
  * @author Rossen Stoyanchev
  * @since 6.0
+ * @see org.springframework.web.client.support.RestTemplateAdapter
  * @see org.springframework.web.reactive.function.client.support.WebClientAdapter
  */
 public final class HttpServiceProxyFactory {
@@ -107,6 +108,7 @@ public final class HttpServiceProxyFactory {
 
 	/**
 	 * Return a builder that's initialized with the given client.
+	 * @since 6.1
 	 */
 	public static Builder builderFor(HttpExchangeAdapter exchangeAdapter) {
 		return new Builder().exchangeAdapter(exchangeAdapter);
@@ -114,7 +116,8 @@ public final class HttpServiceProxyFactory {
 
 	/**
 	 * Return a builder that's initialized with the given client.
-	 * @deprecated in favor of {@link #builderFor(HttpExchangeAdapter)}
+	 * @deprecated in favor of {@link #builderFor(HttpExchangeAdapter)};
+	 * to be removed in 6.2.
 	 */
 	@SuppressWarnings("removal")
 	@Deprecated(since = "6.1", forRemoval = true)
@@ -164,7 +167,8 @@ public final class HttpServiceProxyFactory {
 		 * Provide the HTTP client to perform requests through.
 		 * @param clientAdapter a client adapted to {@link HttpClientAdapter}
 		 * @return this same builder instance
-		 * @deprecated in favor of {@link #exchangeAdapter(HttpExchangeAdapter)}
+		 * @deprecated in favor of {@link #exchangeAdapter(HttpExchangeAdapter)};
+		 * to be removed in 6.2
 		 */
 		@SuppressWarnings("removal")
 		@Deprecated(since = "6.1", forRemoval = true)
@@ -260,10 +264,10 @@ public final class HttpServiceProxyFactory {
 
 			// Annotation-based
 			resolvers.add(new RequestHeaderArgumentResolver(service));
-			resolvers.add(new RequestBodyArgumentResolver());
+			resolvers.add(new RequestBodyArgumentResolver(this.exchangeAdapter));
 			resolvers.add(new PathVariableArgumentResolver(service));
 			resolvers.add(new RequestParamArgumentResolver(service));
-			resolvers.add(new RequestPartArgumentResolver());
+			resolvers.add(new RequestPartArgumentResolver(this.exchangeAdapter));
 			resolvers.add(new CookieValueArgumentResolver(service));
 			if (this.exchangeAdapter.supportsRequestAttributes()) {
 				resolvers.add(new RequestAttributeArgumentResolver());

spring-web/src/main/java/org/springframework/web/service/invoker/ReactorHttpExchangeAdapter.java

@@ -28,8 +28,8 @@ import org.springframework.http.ResponseEntity;
 import org.springframework.lang.Nullable;
 
 /**
- * Contract to abstract a Project Reactor, HTTP client to decouple it from the
- * {@linkplain HttpServiceProxyFactory#createClient(Class) HTTP service proxy}.
+ * Contract to abstract a reactive, HTTP client from
+ * {@linkplain HttpServiceProxyFactory} and make it pluggable.
  *
  * @author Rossen Stoyanchev
  * @since 6.1

spring-web/src/main/java/org/springframework/web/service/invoker/RequestBodyArgumentResolver.java

@@ -22,6 +22,7 @@ import org.springframework.core.ReactiveAdapter;
 import org.springframework.core.ReactiveAdapterRegistry;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
+import org.springframework.util.ClassUtils;
 import org.springframework.web.bind.annotation.RequestBody;
 
 /**
@@ -33,23 +34,28 @@ import org.springframework.web.bind.annotation.RequestBody;
  */
 public class RequestBodyArgumentResolver implements HttpServiceArgumentResolver {
 
+	private static final boolean REACTOR_PRESENT =
+			ClassUtils.isPresent("reactor.core.publisher.Mono", RequestBodyArgumentResolver.class.getClassLoader());
+
+
+	@Nullable
 	private final ReactiveAdapterRegistry reactiveAdapterRegistry;
 
 
 	/**
-	 * Default constructor that uses {@link ReactiveAdapterRegistry#getSharedInstance()}.
+	 * Constructor with a {@link HttpExchangeAdapter}, for access to config settings.
 	 * @since 6.1
 	 */
-	public RequestBodyArgumentResolver() {
-		this(ReactiveAdapterRegistry.getSharedInstance());
-	}
-
-	/**
-	 * Constructor with a {@link ReactiveAdapterRegistry}.
-	 */
-	public RequestBodyArgumentResolver(ReactiveAdapterRegistry reactiveAdapterRegistry) {
-		Assert.notNull(reactiveAdapterRegistry, "ReactiveAdapterRegistry is required");
-		this.reactiveAdapterRegistry = reactiveAdapterRegistry;
+	public RequestBodyArgumentResolver(HttpExchangeAdapter exchangeAdapter) {
+		if (REACTOR_PRESENT) {
+			this.reactiveAdapterRegistry =
+					(exchangeAdapter instanceof ReactorHttpExchangeAdapter reactorAdapter ?
+							reactorAdapter.getReactiveAdapterRegistry() :
+							ReactiveAdapterRegistry.getSharedInstance());
+		}
+		else {
+			this.reactiveAdapterRegistry = null;
+		}
 	}
 
 
@@ -63,21 +69,25 @@ public class RequestBodyArgumentResolver implements HttpServiceArgumentResolver
 		}
 
 		if (argument != null) {
-			ReactiveAdapter reactiveAdapter = this.reactiveAdapterRegistry.getAdapter(parameter.getParameterType());
-			if (reactiveAdapter == null) {
-				requestValues.setBodyValue(argument);
-			}
-			else {
-				MethodParameter nestedParameter = parameter.nested();
+			if (this.reactiveAdapterRegistry != null) {
+				ReactiveAdapter adapter = this.reactiveAdapterRegistry.getAdapter(parameter.getParameterType());
+				if (adapter != null) {
+					MethodParameter nestedParameter = parameter.nested();
 
-				String message = "Async type for @RequestBody should produce value(s)";
-				Assert.isTrue(!reactiveAdapter.isNoValue(), message);
-				Assert.isTrue(nestedParameter.getNestedParameterType() != Void.class, message);
+					String message = "Async type for @RequestBody should produce value(s)";
+					Assert.isTrue(!adapter.isNoValue(), message);
+					Assert.isTrue(nestedParameter.getNestedParameterType() != Void.class, message);
 
-				requestValues.setBody(
-						reactiveAdapter.toPublisher(argument),
-						ParameterizedTypeReference.forType(nestedParameter.getNestedGenericParameterType()));
+					requestValues.setBody(
+							adapter.toPublisher(argument),
+							ParameterizedTypeReference.forType(nestedParameter.getNestedGenericParameterType()));
+
+					return true;
+				}
 			}
+
+			// Not a reactive type
+			requestValues.setBodyValue(argument);
 		}
 
 		return true;

spring-web/src/main/java/org/springframework/web/service/invoker/RequestPartArgumentResolver.java

@@ -24,7 +24,9 @@ import org.springframework.core.ReactiveAdapterRegistry;
 import org.springframework.core.ResolvableType;
 import org.springframework.http.HttpEntity;
 import org.springframework.http.codec.multipart.Part;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
+import org.springframework.util.ClassUtils;
 import org.springframework.web.bind.annotation.RequestPart;
 
 /**
@@ -47,22 +49,28 @@ import org.springframework.web.bind.annotation.RequestPart;
  */
 public class RequestPartArgumentResolver extends AbstractNamedValueArgumentResolver {
 
+	private static final boolean REACTOR_PRESENT =
+			ClassUtils.isPresent("reactor.core.publisher.Mono", RequestPartArgumentResolver.class.getClassLoader());
+
+
+	@Nullable
 	private final ReactiveAdapterRegistry reactiveAdapterRegistry;
 
 
 	/**
-	 * Default constructor that uses {@link ReactiveAdapterRegistry#getSharedInstance()}.
+	 * Constructor with a {@link HttpExchangeAdapter}, for access to config settings.
 	 * @since 6.1
 	 */
-	public RequestPartArgumentResolver() {
-		this(ReactiveAdapterRegistry.getSharedInstance());
-	}
-
-	/**
-	 * Constructor with a {@link ReactiveAdapterRegistry}.
-	 */
-	public RequestPartArgumentResolver(ReactiveAdapterRegistry reactiveAdapterRegistry) {
-		this.reactiveAdapterRegistry = reactiveAdapterRegistry;
+	public RequestPartArgumentResolver(HttpExchangeAdapter exchangeAdapter) {
+		if (REACTOR_PRESENT) {
+			this.reactiveAdapterRegistry =
+					(exchangeAdapter instanceof ReactorHttpExchangeAdapter reactorAdapter ?
+							reactorAdapter.getReactiveAdapterRegistry() :
+							ReactiveAdapterRegistry.getSharedInstance());
+		}
+		else {
+			this.reactiveAdapterRegistry = null;
+		}
 	}
 
 
@@ -77,16 +85,18 @@ public class RequestPartArgumentResolver extends AbstractNamedValueArgumentResol
 	protected void addRequestValue(
 			String name, Object value, MethodParameter parameter, HttpRequestValues.Builder requestValues) {
 
-		Class<?> type = parameter.getParameterType();
-		ReactiveAdapter adapter = this.reactiveAdapterRegistry.getAdapter(type);
-		if (adapter != null) {
-			Assert.isTrue(!adapter.isNoValue(), "Expected publisher that produces a value");
-			Publisher<?> publisher = adapter.toPublisher(value);
-			requestValues.addRequestPart(name, publisher, ResolvableType.forMethodParameter(parameter.nested()));
-		}
-		else {
-			requestValues.addRequestPart(name, value);
+		if (this.reactiveAdapterRegistry != null) {
+			Class<?> type = parameter.getParameterType();
+			ReactiveAdapter adapter = this.reactiveAdapterRegistry.getAdapter(type);
+			if (adapter != null) {
+				Assert.isTrue(!adapter.isNoValue(), "Expected publisher that produces a value");
+				Publisher<?> publisher = adapter.toPublisher(value);
+				requestValues.addRequestPart(name, publisher, ResolvableType.forMethodParameter(parameter.nested()));
+				return;
+			}
 		}
+
+		requestValues.addRequestPart(name, value);
 	}
 
 }