Fix zip compression of libs in layered jars

Closes gh-19792

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/main/java/org/springframework/boot/gradle/tasks/bundling/BootJar.java

@@ -23,7 +23,10 @@ import java.io.StringWriter;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
+import java.util.Set;
 import java.util.concurrent.Callable;
+import java.util.stream.Collectors;
+import java.util.stream.StreamSupport;
 
 import org.gradle.api.Action;
 import org.gradle.api.file.CopySpec;
@@ -282,18 +285,29 @@ public class BootJar extends Jar implements BootArchive {
 	 * Returns the {@link ZipCompression} that should be used when adding the file
 	 * represented by the given {@code details} to the jar.
 	 * <p>
-	 * By default, any file in {@code BOOT-INF/lib/} is stored and all other files are
-	 * deflated.
+	 * By default, any file in {@code BOOT-INF/lib/} or
+	 * {@code BOOT-INF/layers/<layer>/lib} is stored and all other files are deflated.
 	 * @param details the details
 	 * @return the compression to use
 	 */
 	protected ZipCompression resolveZipCompression(FileCopyDetails details) {
-		if (details.getRelativePath().getPathString().startsWith("BOOT-INF/lib/")) {
-			return ZipCompression.STORED;
+		String path = details.getRelativePath().getPathString();
+		for (String prefix : getLibPathPrefixes()) {
+			if (path.startsWith(prefix)) {
+				return ZipCompression.STORED;
+			}
 		}
 		return ZipCompression.DEFLATED;
 	}
 
+	private Set<String> getLibPathPrefixes() {
+		if (this.layers == null) {
+			return Collections.singleton("BOOT-INF/lib/");
+		}
+		return StreamSupport.stream(this.layers.spliterator(), false)
+				.map((layer) -> "BOOT-INF/layers/" + layer + "/lib/").collect(Collectors.toSet());
+	}
+
 	private LaunchScriptConfiguration enableLaunchScriptIfNecessary() {
 		LaunchScriptConfiguration launchScript = this.support.getLaunchScript();
 		if (launchScript == null) {

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/test/java/org/springframework/boot/gradle/tasks/bundling/AbstractBootArchiveTests.java

@@ -110,13 +110,15 @@ abstract class AbstractBootArchiveTests<T extends Jar & BootArchive> {
 	}
 
 	@Test
-	void classpathJarsArePackagedBeneathLibPath() throws IOException {
+	void classpathJarsArePackagedBeneathLibPathAndAreStored() throws IOException {
 		this.task.setMainClassName("com.example.Main");
 		this.task.classpath(jarFile("one.jar"), jarFile("two.jar"));
 		executeTask();
 		try (JarFile jarFile = new JarFile(this.task.getArchiveFile().get().getAsFile())) {
-			assertThat(jarFile.getEntry(this.libPath + "one.jar")).isNotNull();
-			assertThat(jarFile.getEntry(this.libPath + "two.jar")).isNotNull();
+			assertThat(jarFile.getEntry(this.libPath + "one.jar")).isNotNull().extracting(ZipEntry::getMethod)
+					.isEqualTo(ZipEntry.STORED);
+			assertThat(jarFile.getEntry(this.libPath + "two.jar")).isNotNull().extracting(ZipEntry::getMethod)
+					.isEqualTo(ZipEntry.STORED);
 		}
 	}
 
@@ -409,6 +411,11 @@ abstract class AbstractBootArchiveTests<T extends Jar & BootArchive> {
 				this.libPath + "third-library.jar");
 	}
 
+	@Test
+	void libEntriesAreStored() throws IOException {
+
+	}
+
 	protected File jarFile(String name) throws IOException {
 		File file = newFile(name);
 		try (JarOutputStream jar = new JarOutputStream(new FileOutputStream(file))) {

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/test/java/org/springframework/boot/gradle/tasks/bundling/BootJarTests.java

@@ -23,6 +23,7 @@ import java.io.InputStreamReader;
 import java.util.List;
 import java.util.jar.JarFile;
 import java.util.stream.Collectors;
+import java.util.zip.ZipEntry;
 
 import org.junit.jupiter.api.Test;
 
@@ -100,6 +101,18 @@ class BootJarTests extends AbstractBootArchiveTests<BootJar> {
 				.contains("BOOT-INF/layers/resources/classes/static/test.css");
 	}
 
+	@Test
+	void whenJarIsLayeredJarsInLibAreStored() throws IOException {
+		try (JarFile jarFile = new JarFile(createLayeredJar())) {
+			assertThat(jarFile.getEntry("BOOT-INF/layers/dependencies/lib/first-library.jar").getMethod())
+					.isEqualTo(ZipEntry.STORED);
+			assertThat(jarFile.getEntry("BOOT-INF/layers/dependencies/lib/second-library.jar").getMethod())
+					.isEqualTo(ZipEntry.STORED);
+			assertThat(jarFile.getEntry("BOOT-INF/layers/snapshot-dependencies/lib/third-library-SNAPSHOT.jar")
+					.getMethod()).isEqualTo(ZipEntry.STORED);
+		}
+	}
+
 	@Test
 	void whenJarIsLayeredClasspathIndexPointsToLayeredLibs() throws IOException {
 		try (JarFile jarFile = new JarFile(createLayeredJar())) {