Use jlink to create a smaller docker image

.dockerignore

@@ -5,6 +5,7 @@
 build/
 src/test/
 src/main/resources/images/
+.gitattributes
 .gitignore
 *.md
 gradlew.bat

Dockerfile

@@ -1,15 +1,15 @@
-FROM eclipse-temurin:21-jdk AS builder
+FROM eclipse-temurin AS builder
 WORKDIR /app
 COPY settings.gradle build.gradle gradlew ./
 COPY gradle ./gradle
 RUN --mount=type=cache,target=/home/gradle/.gradle/caches \
   ./gradlew dependencies --no-daemon
 COPY . .
-RUN ./gradlew shadowJar --no-daemon
+RUN ./gradlew runtime --no-daemon
 
-FROM eclipse-temurin:21-jre-alpine AS bot
-WORKDIR /app
+FROM gcr.io/distroless/base-nossl AS bot
+COPY --from=builder /app/build/jre ./jre
 COPY --from=builder /app/build/libs/Stickerify-shadow.jar .
-COPY --from=mwader/static-ffmpeg:6.0 /ffmpeg /usr/local/bin/
+COPY --from=mwader/static-ffmpeg /ffmpeg /usr/local/bin/
 ENV FFMPEG_PATH=/usr/local/bin/ffmpeg
-CMD ["java", "-jar", "Stickerify-shadow.jar"]
+CMD ["jre/bin/java", "-jar", "Stickerify-shadow.jar"]

build.gradle

@@ -1,6 +1,6 @@
 plugins {
+    alias(libs.plugins.runtime)
     alias(libs.plugins.shadow)
-    id 'application'
     id 'java'
 }
 
@@ -52,6 +52,11 @@ application {
     mainClass = 'com.github.stickerifier.stickerify.runner.Main'
 }
 
+runtime {
+    options = ['--strip-debug', '--no-header-files', '--no-man-pages', '--compress=2']
+    modules = ['java.desktop', 'java.naming', 'java.sql', 'jdk.crypto.ec']
+}
+
 shadowJar {
     archiveBaseName = 'Stickerify'
     archiveClassifier = 'shadow'

gradle/libs.versions.toml

@@ -17,4 +17,5 @@ telegram-bot-api = "com.github.pengrad:java-telegram-bot-api:6.9.1"
 tika = "org.apache.tika:tika-core:2.9.0"
 
 [plugins]
+runtime = "org.beryx.runtime:1.13.0"
 shadow = "com.github.johnrengelman.shadow:8.1.1"

src/main/java/com/github/stickerifier/stickerify/media/MediaHelper.java

@@ -204,13 +204,13 @@ private static boolean isSupportedVideo(String mimeType) {
 	 * @throws TelegramApiException if an error occurred processing passed-in image
 	 */
 	private static File convertToPng(BufferedImage image, String mimeType) throws TelegramApiException {
-		if (isImageCompliant(image, mimeType)) {
-			LOGGER.atInfo().log("The image doesn't need conversion");
+		try {
+			if (isImageCompliant(image, mimeType)) {
+				LOGGER.atInfo().log("The image doesn't need conversion");
 
-			return null;
-		}
+				return null;
+			}
 
-		try {
 			return createPngFile(resizeImage(image));
 		} finally {
 			image.flush();

src/test/java/com/github/stickerifier/stickerify/ResourceHelper.java

@@ -24,6 +24,8 @@ public File createImage(int width, int height, String extension) {
 			ImageIO.write(image, extension, file);
 		} catch (IOException e) {
 			abort("Image could not be written to file [%s].".formatted(file.getName()));
+		} finally {
+			image.flush();
 		}
 
 		return file;