Add Zstandard compression support

Adds a third compression algorithm alongside Brotli and Gzip via the
zstd-jni library. Zstd is enabled by default at level 22 (maximum).
Spring Framework's EncodedResourceResolver does not yet serve .zst
files (spring-projects/spring-framework#36647), so users serving via
Spring's resource chain should set zstdEnabled=false until that change
is released.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: making

README.md

@@ -1,10 +1,10 @@
 # Compression Maven Plugin
 
-A Maven plugin that compresses static resources using [Brotli](https://github.com/google/brotli) and Gzip.
+A Maven plugin that compresses static resources using [Brotli](https://github.com/google/brotli), Gzip, and [Zstandard](https://facebook.github.io/zstd/).
 
 ## When to use this plugin
 
-If your web application serves static resources (JavaScript, CSS, SVG, etc.) and your web server supports serving pre-compressed files, this plugin generates `.br` and `.gz` variants at build time so the server can serve them directly without compressing on every request.
+If your web application serves static resources (JavaScript, CSS, SVG, etc.) and your web server supports serving pre-compressed files, this plugin generates `.br`, `.gz`, and `.zst` variants at build time so the server can serve them directly without compressing on every request.
 
 This plugin is designed to work with Spring Framework's `ResourceResolver` chain. The default resource directories and file extensions match Spring Boot's conventions out of the box. See [Spring Boot integration](#spring-boot-integration) for setup details.
 
@@ -31,6 +31,9 @@ By default, this compresses all text-based static resource files under Spring Bo
 
 - `<filename>.br` -- Brotli compressed (quality 11)
 - `<filename>.gz` -- Gzip compressed
+- `<filename>.zst` -- Zstandard compressed (level 22)
+
+> Note: Spring Framework's `EncodedResourceResolver` does not yet serve pre-compressed `.zst` files. Support is pending in [spring-projects/spring-framework#36647](https://github.com/spring-projects/spring-framework/pull/36647). If you serve assets via Spring's resource chain, set `<zstdEnabled>false</zstdEnabled>` until that change ships in a Spring Framework release.
 
 ### Example: Custom extensions and directories
 
@@ -66,6 +69,22 @@ By default, this compresses all text-based static resource files under Spring Bo
 </configuration>
 ```
 
+### Example: Disable Zstandard
+
+```xml
+<configuration>
+    <zstdEnabled>false</zstdEnabled>
+</configuration>
+```
+
+### Example: Lower Zstandard level for faster builds
+
+```xml
+<configuration>
+    <zstdLevel>3</zstdLevel>
+</configuration>
+```
+
 ### Example: Lower Brotli quality for faster builds
 
 ```xml
@@ -94,6 +113,8 @@ All configuration parameters can be set either in the plugin `<configuration>` b
 | `brotliQuality` | `compression.brotli.quality` | `11` | Brotli compression quality (0-11) |
 | `brotliEnabled` | `compression.brotli.enabled` | `true` | Enable Brotli compression |
 | `gzipEnabled` | `compression.gzip.enabled` | `true` | Enable Gzip compression |
+| `zstdEnabled` | `compression.zstd.enabled` | `true` | Enable Zstandard compression (see Spring Framework note above) |
+| `zstdLevel` | `compression.zstd.level` | `22` | Zstandard compression level (practical range 1-22) |
 | `skip` | `compression.skip` | `false` | Skip the plugin |
 
 ### Default file extensions
@@ -116,6 +137,19 @@ The `brotliQuality` parameter controls the trade-off between compression ratio a
 
 The default value of 11 gives the best compression. For faster builds (e.g., during development), a lower value like 4-6 may be preferable.
 
+### Zstandard level
+
+The `zstdLevel` parameter controls the trade-off between compression ratio and build time:
+
+| Level | Speed | Compression ratio |
+|---|---|---|
+| 1-3 | Fast | Lower |
+| 4-15 | Moderate | Good |
+| 16-19 | Slow | Better |
+| 20-22 | Very slow ("ultra" mode) | Best |
+
+The default value of 22 gives the best compression. Level 3 matches libzstd's own default and produces noticeably faster builds at the cost of a modest reduction in compression ratio. Note that zstd's decompression speed is, by design, largely independent of the compression level used, so a higher level does not slow down clients that serve the resulting `.zst` files.
+
 ## Spring Boot integration
 
 This plugin generates pre-compressed files that Spring Framework's `EncodedResourceResolver` can serve automatically. To enable this, add the following property to your `application.properties`:
@@ -127,6 +161,8 @@ spring.web.resources.chain.compressed=true
 
 When this property is enabled, Spring Boot will look for `.br` or `.gz` variants of the requested resource and serve the compressed version if the client supports it (via the `Accept-Encoding` header).
 
+`.zst` support in `EncodedResourceResolver` is pending upstream (see [spring-projects/spring-framework#36647](https://github.com/spring-projects/spring-framework/pull/36647)). Until that change is released, set `<zstdEnabled>false</zstdEnabled>` if you are serving assets via Spring's resource chain.
+
 For more details, see the Spring documentation:
 
 - [Spring MVC - Static Resources](https://docs.spring.io/spring-framework/reference/web/webmvc/mvc-config/static-resources.html)

pom.xml

@@ -9,7 +9,7 @@
 	<version>0.3.0-SNAPSHOT</version>
 	<packaging>maven-plugin</packaging>
 	<name>compression-maven-plugin</name>
-	<description>A Maven plugin that compresses static resources using Brotli and Gzip</description>
+	<description>A Maven plugin that compresses static resources using Brotli, Gzip, and Zstandard</description>
 
 	<properties>
 		<java.version>17</java.version>
@@ -19,6 +19,7 @@
 		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
 		<maven.version>3.9.14</maven.version>
 		<brotli4j.version>1.22.0</brotli4j.version>
+		<zstd-jni.version>1.5.7-7</zstd-jni.version>
 		<spring-boot.version>4.0.5</spring-boot.version>
 	</properties>
 	<licenses>
@@ -72,6 +73,11 @@
 			<artifactId>brotli4j</artifactId>
 			<version>${brotli4j.version}</version>
 		</dependency>
+		<dependency>
+			<groupId>com.github.luben</groupId>
+			<artifactId>zstd-jni</artifactId>
+			<version>${zstd-jni.version}</version>
+		</dependency>
 		<dependency>
 			<groupId>org.junit.jupiter</groupId>
 			<artifactId>junit-jupiter-api</artifactId>

src/it/basic-compress/verify.groovy

@@ -6,8 +6,11 @@ assert buildLog.contains("Compressed icon.svg") : "Should log compression of ico
 def staticDir = new File(basedir, "target/classes/static")
 assert new File(staticDir, "app.js.br").exists() : "Brotli file should exist for app.js"
 assert new File(staticDir, "app.js.gz").exists() : "Gzip file should exist for app.js"
+assert new File(staticDir, "app.js.zst").exists() : "Zstd file should exist for app.js"
 assert new File(staticDir, "style.css.br").exists() : "Brotli file should exist for style.css"
 assert new File(staticDir, "style.css.gz").exists() : "Gzip file should exist for style.css"
+assert new File(staticDir, "style.css.zst").exists() : "Zstd file should exist for style.css"
 assert new File(staticDir, "icon.svg.br").exists() : "Brotli file should exist for icon.svg"
 assert new File(staticDir, "icon.svg.gz").exists() : "Gzip file should exist for icon.svg"
+assert new File(staticDir, "icon.svg.zst").exists() : "Zstd file should exist for icon.svg"
 assert buildLog.contains("BUILD SUCCESS")

src/it/custom-extensions/verify.groovy

@@ -3,8 +3,11 @@ def staticDir = new File(basedir, "target/classes/static")
 
 assert new File(staticDir, "index.html.br").exists() : "Brotli file should exist for index.html"
 assert new File(staticDir, "index.html.gz").exists() : "Gzip file should exist for index.html"
+assert new File(staticDir, "index.html.zst").exists() : "Zstd file should exist for index.html"
 assert new File(staticDir, "data.json.br").exists() : "Brotli file should exist for data.json"
 assert new File(staticDir, "data.json.gz").exists() : "Gzip file should exist for data.json"
+assert new File(staticDir, "data.json.zst").exists() : "Zstd file should exist for data.json"
 assert !new File(staticDir, "app.js.br").exists() : "JS should not be compressed with custom extensions"
 assert !new File(staticDir, "app.js.gz").exists() : "JS should not be compressed with custom extensions"
+assert !new File(staticDir, "app.js.zst").exists() : "JS should not be compressed with custom extensions"
 assert buildLog.contains("BUILD SUCCESS")

src/it/zstd-enabled/invoker.properties

@@ -0,0 +1 @@
+invoker.goals=clean compile

src/it/zstd-enabled/pom.xml

@@ -0,0 +1,35 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+		 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+		 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+	<modelVersion>4.0.0</modelVersion>
+
+	<groupId>com.example</groupId>
+	<artifactId>zstd-enabled</artifactId>
+	<version>1.0-SNAPSHOT</version>
+
+	<properties>
+		<maven.compiler.release>17</maven.compiler.release>
+		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+	</properties>
+
+	<build>
+		<plugins>
+			<plugin>
+				<groupId>am.ik.maven</groupId>
+				<artifactId>compression-maven-plugin</artifactId>
+				<version>@project.version@</version>
+				<executions>
+					<execution>
+						<goals>
+							<goal>compress</goal>
+						</goals>
+					</execution>
+				</executions>
+				<configuration>
+					<zstdLevel>3</zstdLevel>
+				</configuration>
+			</plugin>
+		</plugins>
+	</build>
+</project>

src/it/zstd-enabled/src/main/resources/static/app.js

@@ -0,0 +1 @@
+console.log("hello world");

src/it/zstd-enabled/verify.groovy

@@ -0,0 +1,9 @@
+def buildLog = new File(basedir, "build.log").text
+assert buildLog.contains("Compressed app.js") : "Should log compression of app.js"
+
+def staticDir = new File(basedir, "target/classes/static")
+assert new File(staticDir, "app.js.zst").exists() : "Zstd file should exist for app.js"
+assert new File(staticDir, "app.js.br").exists() : "Brotli file should still exist for app.js"
+assert new File(staticDir, "app.js.gz").exists() : "Gzip file should still exist for app.js"
+assert buildLog =~ /Compressed app\.js:.*zst:/ : "Build log should include zst size entry"
+assert buildLog.contains("BUILD SUCCESS")

src/main/java/am/ik/maven/compression/CompressMojo.java

@@ -80,6 +80,19 @@ public class CompressMojo extends AbstractMojo {
 	@Parameter(property = "compression.gzip.enabled", defaultValue = "true")
 	private boolean gzipEnabled;
 
+	/**
+	 * Whether to enable Zstandard compression.
+	 */
+	@Parameter(property = "compression.zstd.enabled", defaultValue = "true")
+	private boolean zstdEnabled;
+
+	/**
+	 * Zstandard compression level. The practical range is 1-22, where 22 is the maximum
+	 * ("ultra" mode). Higher values produce smaller files but take longer.
+	 */
+	@Parameter(property = "compression.zstd.level", defaultValue = "22")
+	private int zstdLevel;
+
 	@Override
 	public void execute() throws MojoExecutionException {
 		if (this.skip) {
@@ -99,6 +112,9 @@ public void execute() throws MojoExecutionException {
 		if (this.gzipEnabled) {
 			compressorBuilder.addCompressor(new GzipCompressor());
 		}
+		if (this.zstdEnabled) {
+			compressorBuilder.addCompressor(new ZstdCompressor(this.zstdLevel));
+		}
 		StaticResourceCompressor compressor = compressorBuilder.build();
 
 		Path basePath = this.outputDirectory.toPath();

src/main/java/am/ik/maven/compression/ZstdCompressor.java

@@ -0,0 +1,59 @@
+/*
+ * Copyright 2026 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package am.ik.maven.compression;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+
+import com.github.luben.zstd.Zstd;
+
+/**
+ * {@link ResourceCompressor} implementation using Zstandard compression.
+ */
+public final class ZstdCompressor implements ResourceCompressor {
+
+	private final int level;
+
+	/**
+	 * Creates a new Zstandard compressor with the specified compression level.
+	 * @param level the Zstandard compression level. The practical range is 1-22, where 22
+	 * is the maximum and levels 20-22 enable "ultra" mode (slower and more memory
+	 * intensive but produces the smallest output).
+	 */
+	public ZstdCompressor(int level) {
+		this.level = level;
+	}
+
+	@Override
+	public String suffix() {
+		return ".zst";
+	}
+
+	@Override
+	public String label() {
+		return "zst";
+	}
+
+	@Override
+	public long compress(Path source, Path target) throws IOException {
+		byte[] input = Files.readAllBytes(source);
+		byte[] compressed = Zstd.compress(input, this.level);
+		Files.write(target, compressed);
+		return compressed.length;
+	}
+
+}