Add HttpRequestValues.Processor

Closes gh-34699

Author: rstoyanchev

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

@@ -16,6 +16,7 @@
 
 package org.springframework.web.service.invoker;
 
+import java.lang.reflect.Method;
 import java.net.URI;
 import java.util.Collections;
 import java.util.HashMap;
@@ -176,6 +177,9 @@ public Map<String, Object> getAttributes() {
 	}
 
 
+	/**
+	 * Return a builder for {@link HttpRequestValues}.
+	 */
 	public static Builder builder() {
 		return new Builder();
 	}
@@ -209,6 +213,28 @@ public interface Metadata {
 	}
 
 
+	/**
+	 * A contract that allows further customization of {@link HttpRequestValues}
+	 * in addition to those added by argument resolvers.
+	 * <p>Use {@link HttpServiceProxyFactory.Builder#httpRequestValuesProcessor(Processor)}
+	 * to add such a processor.
+	 * @since 7.0
+	 */
+	public interface Processor {
+
+		/**
+		 * Invoked after argument resolvers have been called, and before the
+		 * {@link HttpRequestValues} is built.
+		 * @param method the {@code @HttpExchange} method
+		 * @param arguments the raw argument values to the method
+		 * @param builder the builder to add request values too; the builder
+		 * also exposes method {@link Metadata} from the {@code HttpExchange} method.
+		 */
+		void process(Method method, @Nullable Object[] arguments, Builder builder);
+
+	}
+
+
 	/**
 	 * Builder for {@link HttpRequestValues}.
 	 */
@@ -238,6 +264,9 @@ public static class Builder implements Metadata {
 
 		private @Nullable Object bodyValue;
 
+		protected Builder() {
+		}
+
 		/**
 		 * Set the HTTP method for the request.
 		 */

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

@@ -77,18 +77,22 @@ final class HttpServiceMethod {
 
 	private final List<HttpServiceArgumentResolver> argumentResolvers;
 
+	private final HttpRequestValues.Processor requestValuesProcessor;
+
 	private final HttpRequestValuesInitializer requestValuesInitializer;
 
 	private final ResponseFunction responseFunction;
 
 
 	HttpServiceMethod(
 			Method method, Class<?> containingClass, List<HttpServiceArgumentResolver> argumentResolvers,
-			HttpExchangeAdapter adapter, @Nullable StringValueResolver embeddedValueResolver) {
+			HttpRequestValues.Processor valuesProcessor, HttpExchangeAdapter adapter,
+			@Nullable StringValueResolver embeddedValueResolver) {
 
 		this.method = method;
 		this.parameters = initMethodParameters(method);
 		this.argumentResolvers = argumentResolvers;
+		this.requestValuesProcessor = valuesProcessor;
 
 		boolean isReactorAdapter = (REACTOR_PRESENT && adapter instanceof ReactorHttpExchangeAdapter);
 
@@ -129,6 +133,7 @@ public Method getMethod() {
 	public @Nullable Object invoke(@Nullable Object[] arguments) {
 		HttpRequestValues.Builder requestValues = this.requestValuesInitializer.initializeRequestValuesBuilder();
 		applyArguments(requestValues, arguments);
+		this.requestValuesProcessor.process(this.method, arguments, requestValues);
 		return this.responseFunction.execute(requestValues.build());
 	}
 

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

@@ -58,15 +58,19 @@ public final class HttpServiceProxyFactory {
 
 	private final List<HttpServiceArgumentResolver> argumentResolvers;
 
+	private final HttpRequestValues.Processor requestValuesProcessor;
+
 	private final @Nullable StringValueResolver embeddedValueResolver;
 
 
 	private HttpServiceProxyFactory(
 			HttpExchangeAdapter exchangeAdapter, List<HttpServiceArgumentResolver> argumentResolvers,
+			List<HttpRequestValues.Processor> requestValuesProcessor,
 			@Nullable StringValueResolver embeddedValueResolver) {
 
 		this.exchangeAdapter = exchangeAdapter;
 		this.argumentResolvers = argumentResolvers;
+		this.requestValuesProcessor = new CompositeHttpRequestValuesProcessor(requestValuesProcessor);
 		this.embeddedValueResolver = embeddedValueResolver;
 	}
 
@@ -97,7 +101,8 @@ private <S> HttpServiceMethod createHttpServiceMethod(Class<S> serviceType, Meth
 				"No argument resolvers: afterPropertiesSet was not called");
 
 		return new HttpServiceMethod(
-				method, serviceType, this.argumentResolvers, this.exchangeAdapter, this.embeddedValueResolver);
+				method, serviceType, this.argumentResolvers, this.requestValuesProcessor,
+				this.exchangeAdapter, this.embeddedValueResolver);
 	}
 
 
@@ -126,6 +131,8 @@ public static final class Builder {
 
 		private final List<HttpServiceArgumentResolver> customArgumentResolvers = new ArrayList<>();
 
+		private final List<HttpRequestValues.Processor> requestValuesProcessors = new ArrayList<>();
+
 		private @Nullable ConversionService conversionService;
 
 		private @Nullable StringValueResolver embeddedValueResolver;
@@ -154,6 +161,18 @@ public Builder customArgumentResolver(HttpServiceArgumentResolver resolver) {
 			return this;
 		}
 
+		/**
+		 * Register an {@link HttpRequestValues} processor that can further
+		 * customize request values based on the method and all arguments.
+		 * @param processor the processor to add
+		 * @return this same builder instance
+		 * @since 7.0
+		 */
+		public Builder httpRequestValuesProcessor(HttpRequestValues.Processor processor) {
+			this.requestValuesProcessors.add(processor);
+			return this;
+		}
+
 		/**
 		 * Set the {@link ConversionService} to use where input values need to
 		 * be formatted as Strings.
@@ -183,7 +202,8 @@ public HttpServiceProxyFactory build() {
 			Assert.notNull(this.exchangeAdapter, "HttpClientAdapter is required");
 
 			return new HttpServiceProxyFactory(
-					this.exchangeAdapter, initArgumentResolvers(), this.embeddedValueResolver);
+					this.exchangeAdapter, initArgumentResolvers(), this.requestValuesProcessors,
+					this.embeddedValueResolver);
 		}
 
 		@SuppressWarnings({"DataFlowIssue", "NullAway"})
@@ -251,7 +271,21 @@ private static Object[] resolveCoroutinesArguments(@Nullable Object[] args) {
 			System.arraycopy(args, 0, functionArgs, 0, args.length - 1);
 			return functionArgs;
 		}
+	}
+
+
+	/**
+	 * Processor that delegates to a list of other processors.
+	 */
+	private record CompositeHttpRequestValuesProcessor(List<HttpRequestValues.Processor> processors)
+			implements HttpRequestValues.Processor {
 
+		@Override
+		public void process(Method method, @Nullable Object[] arguments, HttpRequestValues.Builder builder) {
+			for (HttpRequestValues.Processor processor : this.processors) {
+				processor.process(method, arguments, builder);
+			}
+		}
 	}
 
 }

Diff for: spring-web/src/main/java/org/springframework/web/service/invoker/ReactiveHttpRequestValues.java

@@ -94,6 +94,9 @@ public static final class Builder extends HttpRequestValues.Builder {
 
 		private @Nullable ParameterizedTypeReference<?> bodyElementType;
 
+		private Builder() {
+		}
+
 		@Override
 		public Builder setHttpMethod(HttpMethod httpMethod) {
 			super.setHttpMethod(httpMethod);

Diff for: spring-web/src/test/java/org/springframework/web/service/invoker/HttpServiceMethodTests.java

@@ -198,12 +198,12 @@ void methodAnnotatedService() {
 
 	@Test
 	void typeAndMethodAnnotatedService() {
-		HttpServiceProxyFactory proxyFactory = HttpServiceProxyFactory.builder()
-			.exchangeAdapter(this.client)
-			.embeddedValueResolver(value -> (value.equals("${baseUrl}") ? "/base" : value))
-			.build();
 
-		MethodLevelAnnotatedService service = proxyFactory.createClient(TypeAndMethodLevelAnnotatedService.class);
+		MethodLevelAnnotatedService service = HttpServiceProxyFactory.builder()
+				.exchangeAdapter(this.client)
+				.embeddedValueResolver(value -> (value.equals("${baseUrl}") ? "/base" : value))
+				.build()
+				.createClient(TypeAndMethodLevelAnnotatedService.class);
 
 		service.performGet();
 
@@ -222,6 +222,19 @@ void typeAndMethodAnnotatedService() {
 		assertThat(requestValues.getHeaders().getAccept()).containsOnly(MediaType.APPLICATION_JSON);
 	}
 
+	@Test
+	void httpRequestValuesProcessor() {
+
+		HttpServiceProxyFactory.builder()
+				.exchangeAdapter(this.client)
+				.httpRequestValuesProcessor((m, a, builder) -> builder.addAttribute("foo", "a"))
+				.build()
+				.createClient(Service.class)
+				.execute();
+
+		assertThat(this.client.getRequestValues().getAttributes().get("foo")).isEqualTo("a");
+	}
+
 	@Test  // gh-32049
 	void multipleAnnotationsAtClassLevel() {
 		Class<?> serviceInterface = MultipleClassLevelAnnotationsService.class;