Add chaining methods to ClientHttpRequestInterceptor

See gh-34169

Author: rstoyanchev

spring-web/src/main/java/org/springframework/http/client/ClientHttpRequestInterceptor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2024 the original author or authors.
+ * Copyright 2002-2025 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.
@@ -19,6 +19,7 @@
 import java.io.IOException;
 
 import org.springframework.http.HttpRequest;
+import org.springframework.util.Assert;
 
 /**
  * Contract to intercept client-side HTTP requests. Implementations can be
@@ -60,4 +61,32 @@ public interface ClientHttpRequestInterceptor {
 	ClientHttpResponse intercept(HttpRequest request, byte[] body, ClientHttpRequestExecution execution)
 			throws IOException;
 
+	/**
+	 * Return a new interceptor that invokes {@code this} interceptor first, and
+	 * then the one that's passed in.
+	 * @param interceptor the next interceptor
+	 * @return a new interceptor that chains the two
+	 * @since 7.0
+	 */
+	default ClientHttpRequestInterceptor andThen(ClientHttpRequestInterceptor interceptor) {
+		Assert.notNull(interceptor, "ClientHttpRequestInterceptor must not be null");
+		return (request, body, execution) -> {
+			ClientHttpRequestExecution nextExecution =
+					(nextRequest, nextBody) -> interceptor.intercept(nextRequest, nextBody, execution);
+			return intercept(request, body, nextExecution);
+		};
+	}
+
+	/**
+	 * Return a new execution that invokes {@code this} interceptor, and then
+	 * delegates to the given execution.
+	 * @param execution the execution to delegate to
+	 * @return a new execution instance
+	 * @since 7.0
+	 */
+	default ClientHttpRequestExecution apply(ClientHttpRequestExecution execution) {
+		Assert.notNull(execution, "ClientHttpRequestExecution must not be null");
+		return (request, body) -> intercept(request, body, execution);
+	}
+
 }

spring-web/src/main/java/org/springframework/http/client/InterceptingClientHttpRequest.java

@@ -20,7 +20,6 @@
 import java.io.OutputStream;
 import java.net.URI;
 import java.util.List;
-import java.util.ListIterator;
 
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpMethod;
@@ -69,39 +68,23 @@ public URI getURI() {
 
 	@Override
 	protected final ClientHttpResponse executeInternal(HttpHeaders headers, byte[] bufferedOutput) throws IOException {
-		ClientHttpRequestExecution requestExecution = new DelegatingRequestExecution(this.requestFactory);
-		ListIterator<ClientHttpRequestInterceptor> iterator = this.interceptors.listIterator(this.interceptors.size());
-		while (iterator.hasPrevious()) {
-			ClientHttpRequestInterceptor interceptor = iterator.previous();
-			requestExecution = new InterceptingRequestExecution(interceptor, requestExecution);
-		}
-		return requestExecution.execute(this, bufferedOutput);
+		return getExecution().execute(this, bufferedOutput);
 	}
 
-
-	private static class InterceptingRequestExecution implements ClientHttpRequestExecution {
-
-		private final ClientHttpRequestInterceptor interceptor;
-
-		private final ClientHttpRequestExecution nextExecution;
-
-		public InterceptingRequestExecution(ClientHttpRequestInterceptor interceptor, ClientHttpRequestExecution nextExecution) {
-			this.interceptor = interceptor;
-			this.nextExecution = nextExecution;
-		}
-
-		@Override
-		public ClientHttpResponse execute(HttpRequest request, byte[] body) throws IOException {
-			return this.interceptor.intercept(request, body, this.nextExecution);
-		}
-
+	private ClientHttpRequestExecution getExecution() {
+		ClientHttpRequestExecution execution = new EndOfChainRequestExecution(this.requestFactory);
+		return this.interceptors.stream()
+				.reduce(ClientHttpRequestInterceptor::andThen)
+				.map(interceptor -> interceptor.apply(execution))
+				.orElse(execution);
 	}
 
-	private static class DelegatingRequestExecution implements ClientHttpRequestExecution {
+
+	private static class EndOfChainRequestExecution implements ClientHttpRequestExecution {
 
 		private final ClientHttpRequestFactory requestFactory;
 
-		public DelegatingRequestExecution(ClientHttpRequestFactory requestFactory) {
+		public EndOfChainRequestExecution(ClientHttpRequestFactory requestFactory) {
 			this.requestFactory = requestFactory;
 		}