Replace Void with void on exchange method

See gh-30117

spring-web/src/main/java/org/springframework/web/client/support/RestTemplateAdapter.java

@@ -54,9 +54,8 @@ public final class RestTemplateAdapter implements HttpExchangeAdapter {
 	}
 
 	@Override
-	public Void exchange(HttpRequestValues requestValues) {
+	public void exchange(HttpRequestValues requestValues) {
 		this.restTemplate.exchange(newRequest(requestValues), Void.class);
-		return null;
 	}
 
 	@Override

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

@@ -91,12 +91,12 @@ public abstract class AbstractReactorHttpExchangeAdapter
 	}
 
 	@Override
-	public Void exchange(HttpRequestValues requestValues) {
+	public void exchange(HttpRequestValues requestValues) {
 		if (this.blockTimeout != null) {
-			return exchangeForMono(requestValues).block(this.blockTimeout);
+			exchangeForMono(requestValues).block(this.blockTimeout);
 		}
 		else {
-			return exchangeForMono(requestValues).block();
+			exchangeForMono(requestValues).block();
 		}
 	}
 

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

@@ -34,7 +34,7 @@ public interface HttpExchangeAdapter {
 	 * Perform the given request, and release the response content, if any.
 	 * @param requestValues the request to perform
 	 */
-	Void exchange(HttpRequestValues requestValues);
+	void exchange(HttpRequestValues requestValues);
 
 	/**
 	 * Perform the given request, release the response content, and return the

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

@@ -301,7 +301,10 @@ final class HttpServiceMethod {
 
 			Function<HttpRequestValues, Object> responseFunction;
 			if (actualReturnType.equals(void.class) || actualReturnType.equals(Void.class)) {
-				responseFunction = client::exchange;
+				responseFunction = requestValues -> {
+					client.exchange(requestValues);
+					return null;
+				};
 			}
 			else if (actualReturnType.equals(HttpHeaders.class)) {
 				responseFunction = request -> processResponse(client.exchangeForHeaders(request),

spring-web/src/test/java/org/springframework/web/service/invoker/TestHttpExchangeAdapter.java

@@ -59,9 +59,8 @@ public class TestHttpExchangeAdapter implements HttpExchangeAdapter, TestAdapter
 	}
 
 	@Override
-	public Void exchange(HttpRequestValues requestValues) {
+	public void exchange(HttpRequestValues requestValues) {
 		saveInput("void", requestValues, null);
-		return null;
 	}
 
 	@Override