Support flat jar layering with layertools

Update layertools to support the flat jar format. Layers are now
determined by reading the `layers.idx` file.

Closes gh-20813

Author: mbhave

spring-boot-project/spring-boot-tools/spring-boot-jarmode-layertools/src/main/java/org/springframework/boot/jarmode/layertools/IndexedLayers.java

@@ -20,59 +20,52 @@
 import java.io.IOException;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.NoSuchFileException;
-import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Map;
 import java.util.jar.JarFile;
-import java.util.regex.Matcher;
-import java.util.regex.Pattern;
-import java.util.stream.Collectors;
 import java.util.zip.ZipEntry;
 
 import org.springframework.util.Assert;
+import org.springframework.util.LinkedMultiValueMap;
+import org.springframework.util.MultiValueMap;
 import org.springframework.util.StreamUtils;
 
 /**
  * {@link Layers} implementation backed by a {@code BOOT-INF/layers.idx} file.
  *
  * @author Phillip Webb
+ * @author Madhura Bhave
  */
 class IndexedLayers implements Layers {
 
-	private static final String APPLICATION_LAYER = "application";
-
-	private static final String SPRING_BOOT_APPLICATION_LAYER = "springbootapplication";
-
-	private static final Pattern LAYER_PATTERN = Pattern.compile("^BOOT-INF\\/layers\\/([a-zA-Z0-9-]+)\\/.*$");
-
-	private List<String> layers;
+	private MultiValueMap<String, String> layers = new LinkedMultiValueMap<>();
 
 	IndexedLayers(String indexFile) {
 		String[] lines = indexFile.split("\n");
-		this.layers = Arrays.stream(lines).map(String::trim).filter((line) -> !line.isEmpty())
-				.collect(Collectors.toCollection(ArrayList::new));
+		Arrays.stream(lines).map(String::trim).filter((line) -> !line.isEmpty()).forEach((line) -> {
+			String[] content = line.split(" ");
+			Assert.state(content.length == 2, "Layer index file is malformed");
+			this.layers.add(content[0], content[1]);
+		});
 		Assert.state(!this.layers.isEmpty(), "Empty layer index file loaded");
-		if (!this.layers.contains(APPLICATION_LAYER)) {
-			this.layers.add(0, SPRING_BOOT_APPLICATION_LAYER);
-		}
 	}
 
 	@Override
 	public Iterator<String> iterator() {
-		return this.layers.iterator();
+		return this.layers.keySet().iterator();
 	}
 
 	@Override
 	public String getLayer(ZipEntry entry) {
 		String name = entry.getName();
-		Matcher matcher = LAYER_PATTERN.matcher(name);
-		if (matcher.matches()) {
-			String layer = matcher.group(1);
-			Assert.state(this.layers.contains(layer), () -> "Unexpected layer '" + layer + "'");
-			return layer;
+		for (Map.Entry<String, List<String>> indexEntry : this.layers.entrySet()) {
+			if (indexEntry.getValue().contains(name)) {
+				return indexEntry.getKey();
+			}
 		}
-		return this.layers.contains(APPLICATION_LAYER) ? APPLICATION_LAYER : SPRING_BOOT_APPLICATION_LAYER;
+		throw new IllegalStateException("No layer defined in index for file '" + name + "'");
 	}
 
 	/**

spring-boot-project/spring-boot-tools/spring-boot-jarmode-layertools/src/test/java/org/springframework/boot/jarmode/layertools/HelpCommandTests.java

@@ -77,10 +77,10 @@ private File createJarFile(String name) throws IOException {
 			JarEntry indexEntry = new JarEntry("BOOT-INF/layers.idx");
 			jarOutputStream.putNextEntry(indexEntry);
 			Writer writer = new OutputStreamWriter(jarOutputStream, StandardCharsets.UTF_8);
-			writer.write("a\n");
-			writer.write("b\n");
-			writer.write("c\n");
-			writer.write("d\n");
+			writer.write("0001 BOOT-INF/lib/a.jar\n");
+			writer.write("0001 BOOT-INF/lib/b.jar\n");
+			writer.write("0002 BOOT-INF/lib/c.jar\n");
+			writer.write("0003 BOOT-INF/lib/d.jar\n");
 			writer.flush();
 		}
 		return file;

spring-boot-project/spring-boot-tools/spring-boot-jarmode-layertools/src/test/java/org/springframework/boot/jarmode/layertools/IndexedLayersTests.java

@@ -16,10 +16,14 @@
 
 package org.springframework.boot.jarmode.layertools;
 
+import java.io.InputStreamReader;
 import java.util.zip.ZipEntry;
 
 import org.junit.jupiter.api.Test;
 
+import org.springframework.core.io.ClassPathResource;
+import org.springframework.util.FileCopyUtils;
+
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatIllegalStateException;
 import static org.mockito.BDDMockito.given;
@@ -29,6 +33,7 @@
  * Tests for {@link IndexedLayers}.
  *
  * @author Phillip Webb
+ * @author Madhura Bhave
  */
 class IndexedLayersTests {
 
@@ -39,41 +44,35 @@ void createWhenIndexFileIsEmptyThrowsException() {
 	}
 
 	@Test
-	void createWhenIndexFileHasNoApplicationLayerAddSpringBootApplication() {
-		IndexedLayers layers = new IndexedLayers("test");
-		assertThat(layers).contains("springbootapplication");
+	void createWhenIndexFileIsMalformedThrowsException() throws Exception {
+		assertThatIllegalStateException().isThrownBy(() -> new IndexedLayers("test"))
+				.withMessage("Layer index file is malformed");
 	}
 
 	@Test
-	void iteratorReturnsLayers() {
-		IndexedLayers layers = new IndexedLayers("test\napplication");
+	void iteratorReturnsLayers() throws Exception {
+		IndexedLayers layers = new IndexedLayers(getIndex());
 		assertThat(layers).containsExactly("test", "application");
 	}
 
 	@Test
-	void getLayerWhenMatchesLayerPatterReturnsLayer() {
-		IndexedLayers layers = new IndexedLayers("test");
-		assertThat(layers.getLayer(mockEntry("BOOT-INF/layers/test/lib/file.jar"))).isEqualTo("test");
+	void getLayerWhenMatchesNameReturnsLayer() throws Exception {
+		IndexedLayers layers = new IndexedLayers(getIndex());
+		assertThat(layers.getLayer(mockEntry("BOOT-INF/lib/a.jar"))).isEqualTo("test");
+		assertThat(layers.getLayer(mockEntry("BOOT-INF/classes/Demo.class"))).isEqualTo("application");
 	}
 
 	@Test
-	void getLayerWhenMatchesLayerPatterForMissingLayerThrowsException() {
-		IndexedLayers layers = new IndexedLayers("test");
-		assertThatIllegalStateException()
-				.isThrownBy(() -> layers.getLayer(mockEntry("BOOT-INF/layers/missing/lib/file.jar")))
-				.withMessage("Unexpected layer 'missing'");
+	void getLayerWhenMatchesNameForMissingLayerThrowsException() throws Exception {
+		IndexedLayers layers = new IndexedLayers(getIndex());
+		assertThatIllegalStateException().isThrownBy(() -> layers.getLayer(mockEntry("file.jar")))
+				.withMessage("No layer defined in index for file " + "'file.jar'");
 	}
 
-	@Test
-	void getLayerWhenDoesNotMatchLayerPatternReturnsApplication() {
-		IndexedLayers layers = new IndexedLayers("test\napplication");
-		assertThat(layers.getLayer(mockEntry("META-INF/MANIFEST.MF"))).isEqualTo("application");
-	}
-
-	@Test
-	void getLayerWhenDoesNotMatchLayerPatternAndHasNoApplicationLayerReturnsSpringApplication() {
-		IndexedLayers layers = new IndexedLayers("test");
-		assertThat(layers.getLayer(mockEntry("META-INF/MANIFEST.MF"))).isEqualTo("springbootapplication");
+	private String getIndex() throws Exception {
+		ClassPathResource resource = new ClassPathResource("test-layers.idx", getClass());
+		InputStreamReader reader = new InputStreamReader(resource.getInputStream());
+		return FileCopyUtils.copyToString(reader);
 	}
 
 	private ZipEntry mockEntry(String name) {

spring-boot-project/spring-boot-tools/spring-boot-jarmode-layertools/src/test/java/org/springframework/boot/jarmode/layertools/LayerToolsJarModeTests.java

@@ -85,10 +85,10 @@ private File createJarFile(String name) throws IOException {
 			JarEntry indexEntry = new JarEntry("BOOT-INF/layers.idx");
 			jarOutputStream.putNextEntry(indexEntry);
 			Writer writer = new OutputStreamWriter(jarOutputStream, StandardCharsets.UTF_8);
-			writer.write("a\n");
-			writer.write("b\n");
-			writer.write("c\n");
-			writer.write("d\n");
+			writer.write("0001 BOOT-INF/lib/a.jar\n");
+			writer.write("0001 BOOT-INF/lib/b.jar\n");
+			writer.write("0002 BOOT-INF/lib/c.jar\n");
+			writer.write("0003 BOOT-INF/lib/d.jar\n");
 			writer.flush();
 		}
 		return file;

spring-boot-project/spring-boot-tools/spring-boot-jarmode-layertools/src/test/java/org/springframework/boot/jarmode/layertools/ListCommandTests.java

@@ -39,6 +39,7 @@
  * Tests for {@link ListCommand}.
  *
  * @author Phillip Webb
+ * @author Madhura Bhave
  */
 class ListCommandTests {
 
@@ -74,7 +75,7 @@ private File createJarFile(String name) throws IOException {
 		File file = new File(this.temp, name);
 		try (ZipOutputStream jarOutputStream = new ZipOutputStream(new FileOutputStream(file))) {
 			writeLayersIndex(jarOutputStream);
-			String entryPrefix = "BOOT-INF/layers/";
+			String entryPrefix = "BOOT-INF/lib/";
 			jarOutputStream.putNextEntry(new ZipEntry(entryPrefix + "a/"));
 			jarOutputStream.closeEntry();
 			jarOutputStream.putNextEntry(new ZipEntry(entryPrefix + "a/a.jar"));
@@ -97,10 +98,10 @@ private void writeLayersIndex(ZipOutputStream out) throws IOException {
 		JarEntry indexEntry = new JarEntry("BOOT-INF/layers.idx");
 		out.putNextEntry(indexEntry);
 		Writer writer = new OutputStreamWriter(out, StandardCharsets.UTF_8);
-		writer.write("a\n");
-		writer.write("b\n");
-		writer.write("c\n");
-		writer.write("d\n");
+		writer.write("0001 BOOT-INF/lib/a.jar\n");
+		writer.write("0001 BOOT-INF/lib/b.jar\n");
+		writer.write("0002 BOOT-INF/lib/c.jar\n");
+		writer.write("0003 BOOT-INF/lib/d.jar\n");
 		writer.flush();
 	}
 

spring-boot-project/spring-boot-tools/spring-boot-jarmode-layertools/src/test/resources/org/springframework/boot/jarmode/layertools/list-output.txt

@@ -1,5 +1,3 @@
-springbootapplication
-a
-b
-c
-d
+0001
+0002
+0003

spring-boot-project/spring-boot-tools/spring-boot-jarmode-layertools/src/test/resources/org/springframework/boot/jarmode/layertools/test-layers.idx

@@ -0,0 +1,3 @@
+test BOOT-INF/lib/a.jar
+test BOOT-INF/lib/b.jar
+application BOOT-INF/classes/Demo.class