validate zstd compression

build.gradle

@@ -121,6 +121,7 @@ ext {
 
 	// Testing
 	brotli4jVersion = '1.16.0'
+	zstdJniVersion = '1.5.6-1'
 	jacksonDatabindVersion = '2.17.0'
 	testAddonVersion = reactorCoreVersion
 	assertJVersion = '3.25.3'

reactor-netty-http/build.gradle

@@ -150,6 +150,9 @@ dependencies {
 	testRuntimeOnly "org.slf4j:jcl-over-slf4j:$slf4jVersion"
 	testRuntimeOnly "ch.qos.logback:logback-classic:$logbackVersion"
 
+	// Needed for zstd compression
+	testImplementation "com.github.luben:zstd-jni:$zstdJniVersion"
+
 	// Needed for Brotli compression
 	testImplementation "com.aayushatharva.brotli4j:brotli4j:$brotli4jVersion"
 	if (osdetector.classifier == "linux-aarch_64" || osdetector.classifier == "osx-aarch_64") {

reactor-netty-http/src/test/java/reactor/netty/http/HttpCompressionClientServerTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017-2023 VMware, Inc. or its affiliates, All Rights Reserved.
+ * Copyright (c) 2017-2024 VMware, Inc. or its affiliates, All Rights Reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -29,6 +29,7 @@
 import com.aayushatharva.brotli4j.decoder.DirectDecompress;
 import io.netty.buffer.Unpooled;
 import io.netty.handler.codec.compression.Brotli;
+import io.netty.handler.codec.compression.Zstd;
 import io.netty.handler.codec.http.HttpHeaders;
 import io.netty.handler.ssl.util.InsecureTrustManagerFactory;
 import io.netty.handler.ssl.util.SelfSignedCertificate;
@@ -225,6 +226,37 @@ void brotliServerCompressionEnabled(HttpServer server, HttpClient client) throws
 		assertThat(new String(decompressedData, Charset.defaultCharset())).isEqualTo("reply");
 	}
 
+	@ParameterizedCompressionTest
+	void zstdServerCompressionEnabled(HttpServer server, HttpClient client) throws Exception {
+		assertThat(Zstd.isAvailable()).isTrue();
+		disposableServer =
+				server.compress(true)
+						.handle((in, out) -> out.sendString(Mono.just("reply")))
+						.bindNow(Duration.ofSeconds(10));
+
+		//don't activate compression on the client options to avoid auto-handling (which removes the header)
+		Tuple2<byte[], HttpHeaders> resp =
+				//edit the header manually to attempt to trigger compression on server side
+				client.port(disposableServer.port())
+						.compress(false)
+						.headers(h -> h.add("Accept-Encoding", "zstd, gzip"))
+						.get()
+						.uri("/test")
+						.responseSingle((res, buf) -> buf.asByteArray()
+								.zipWith(Mono.just(res.responseHeaders())))
+						.block(Duration.ofSeconds(10));
+
+		assertThat(resp).isNotNull();
+		assertThat(resp.getT2().get("content-encoding")).isEqualTo("zstd");
+
+		final byte[] compressedData = resp.getT1();
+		assertThat(new String(compressedData, Charset.defaultCharset())).isNotEqualTo("reply");
+
+		final byte[] decompressedData = com.github.luben.zstd.Zstd.decompress(compressedData, 1_000);
+		assertThat(decompressedData).isNotEmpty();
+		assertThat(new String(decompressedData, Charset.defaultCharset())).isEqualTo("reply");
+	}
+
 	@ParameterizedCompressionTest
 	void serverCompressionEnabledSmallResponse(HttpServer server, HttpClient client) {
 		disposableServer =