Polish loader and loader-tools

Polish and refactor `spring-boot-loader` and `spring-boot-loader-tools`
to make it easier to add indexing and layering support.

Closes gh-19766

Author: philwebb

spring-boot-project/spring-boot-tools/spring-boot-loader-tools/src/main/java/org/springframework/boot/loader/tools/JarWriter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 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.
@@ -56,12 +56,14 @@
  */
 public class JarWriter implements LoaderClassesWriter, AutoCloseable {
 
-	private static final UnpackHandler NEVER_UNPACK = new NeverUnpackHandler();
-
 	private static final String NESTED_LOADER_JAR = "META-INF/loader/spring-boot-loader.jar";
 
 	private static final int BUFFER_SIZE = 32 * 1024;
 
+	private static final int UNIX_FILE_MODE = UnixStat.FILE_FLAG | UnixStat.DEFAULT_FILE_PERM;
+
+	private static final int UNIX_DIR_MODE = UnixStat.DIR_FLAG | UnixStat.DEFAULT_DIR_PERM;
+
 	private final JarArchiveOutputStream jarOutput;
 
 	private final Set<String> writtenEntries = new HashSet<>();
@@ -121,11 +123,11 @@ public void writeManifest(Manifest manifest) throws IOException {
 	 * @throws IOException if the entries cannot be written
 	 */
 	public void writeEntries(JarFile jarFile) throws IOException {
-		this.writeEntries(jarFile, new IdentityEntryTransformer(), NEVER_UNPACK);
+		this.writeEntries(jarFile, EntryTransformer.NONE, UnpackHandler.NEVER);
 	}
 
 	void writeEntries(JarFile jarFile, UnpackHandler unpackHandler) throws IOException {
-		this.writeEntries(jarFile, new IdentityEntryTransformer(), unpackHandler);
+		this.writeEntries(jarFile, EntryTransformer.NONE, unpackHandler);
 	}
 
 	void writeEntries(JarFile jarFile, EntryTransformer entryTransformer, UnpackHandler unpackHandler)
@@ -244,7 +246,7 @@ public void close() throws IOException {
 	}
 
 	private void writeEntry(JarArchiveEntry entry, EntryWriter entryWriter) throws IOException {
-		writeEntry(entry, entryWriter, NEVER_UNPACK);
+		writeEntry(entry, entryWriter, UnpackHandler.NEVER);
 	}
 
 	/**
@@ -257,22 +259,10 @@ private void writeEntry(JarArchiveEntry entry, EntryWriter entryWriter) throws I
 	 */
 	private void writeEntry(JarArchiveEntry entry, EntryWriter entryWriter, UnpackHandler unpackHandler)
 			throws IOException {
-		String parent = entry.getName();
-		if (parent.endsWith("/")) {
-			parent = parent.substring(0, parent.length() - 1);
-			entry.setUnixMode(UnixStat.DIR_FLAG | UnixStat.DEFAULT_DIR_PERM);
-		}
-		else {
-			entry.setUnixMode(UnixStat.FILE_FLAG | UnixStat.DEFAULT_FILE_PERM);
-		}
-		if (parent.lastIndexOf('/') != -1) {
-			parent = parent.substring(0, parent.lastIndexOf('/') + 1);
-			if (!parent.isEmpty()) {
-				writeEntry(new JarArchiveEntry(parent), null, unpackHandler);
-			}
-		}
-
-		if (this.writtenEntries.add(entry.getName())) {
+		String name = entry.getName();
+		writeParentFolderEntries(name);
+		if (this.writtenEntries.add(name)) {
+			entry.setUnixMode(name.endsWith("/") ? UNIX_DIR_MODE : UNIX_FILE_MODE);
 			entryWriter = addUnpackCommentIfNecessary(entry, entryWriter, unpackHandler);
 			this.jarOutput.putArchiveEntry(entry);
 			if (entryWriter != null) {
@@ -282,6 +272,16 @@ private void writeEntry(JarArchiveEntry entry, EntryWriter entryWriter, UnpackHa
 		}
 	}
 
+	private void writeParentFolderEntries(String name) throws IOException {
+		String parent = name.endsWith("/") ? name.substring(0, name.length() - 1) : name;
+		while (parent.lastIndexOf('/') != -1) {
+			parent = parent.substring(0, parent.lastIndexOf('/'));
+			if (!parent.isEmpty()) {
+				writeEntry(new JarArchiveEntry(parent + "/"), null, UnpackHandler.NEVER);
+			}
+		}
+	}
+
 	private EntryWriter addUnpackCommentIfNecessary(JarArchiveEntry entry, EntryWriter entryWriter,
 			UnpackHandler unpackHandler) throws IOException {
 		if (entryWriter == null || !unpackHandler.requiresUnpack(entry.getName())) {
@@ -444,21 +444,15 @@ void setupStoredEntry(JarArchiveEntry entry) {
 	 * An {@code EntryTransformer} enables the transformation of {@link JarEntry jar
 	 * entries} during the writing process.
 	 */
+	@FunctionalInterface
 	interface EntryTransformer {
 
-		JarArchiveEntry transform(JarArchiveEntry jarEntry);
-
-	}
-
-	/**
-	 * An {@code EntryTransformer} that returns the entry unchanged.
-	 */
-	private static final class IdentityEntryTransformer implements EntryTransformer {
+		/**
+		 * No-op entity transformer.
+		 */
+		EntryTransformer NONE = (jarEntry) -> jarEntry;
 
-		@Override
-		public JarArchiveEntry transform(JarArchiveEntry jarEntry) {
-			return jarEntry;
-		}
+		JarArchiveEntry transform(JarArchiveEntry jarEntry);
 
 	}
 
@@ -468,23 +462,23 @@ public JarArchiveEntry transform(JarArchiveEntry jarEntry) {
 	 */
 	interface UnpackHandler {
 
-		boolean requiresUnpack(String name);
+		UnpackHandler NEVER = new UnpackHandler() {
 
-		String sha1Hash(String name) throws IOException;
+			@Override
+			public boolean requiresUnpack(String name) {
+				return false;
+			}
 
-	}
+			@Override
+			public String sha1Hash(String name) throws IOException {
+				throw new UnsupportedOperationException();
+			}
 
-	private static final class NeverUnpackHandler implements UnpackHandler {
+		};
 
-		@Override
-		public boolean requiresUnpack(String name) {
-			return false;
-		}
+		boolean requiresUnpack(String name);
 
-		@Override
-		public String sha1Hash(String name) {
-			throw new UnsupportedOperationException();
-		}
+		String sha1Hash(String name) throws IOException;
 
 	}
 

spring-boot-project/spring-boot-tools/spring-boot-loader-tools/src/main/java/org/springframework/boot/loader/tools/Layout.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 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.
@@ -35,13 +35,26 @@ public interface Layout {
 	 */
 	String getLauncherClassName();
 
+	/**
+	 * Returns the destination path for a given library.
+	 * @param libraryName the name of the library (excluding any path)
+	 * @param scope the scope of the library
+	 * @return the location of the library relative to the root of the archive (should end
+	 * with '/') or {@code null} if the library should not be included.
+	 */
+	default String getLibraryLocation(String libraryName, LibraryScope scope) {
+		return getLibraryDestination(libraryName, scope);
+	}
+
 	/**
 	 * Returns the destination path for a given library.
 	 * @param libraryName the name of the library (excluding any path)
 	 * @param scope the scope of the library
 	 * @return the destination relative to the root of the archive (should end with '/')
 	 * or {@code null} if the library should not be included.
+	 * @deprecated since 2.3.0 in favor of {@link #getLibraryLocation}
 	 */
+	@Deprecated
 	String getLibraryDestination(String libraryName, LibraryScope scope);
 
 	/**

spring-boot-project/spring-boot-tools/spring-boot-loader-tools/src/main/java/org/springframework/boot/loader/tools/Layouts.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 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.
@@ -67,6 +67,12 @@ public String getLauncherClassName() {
 			return "org.springframework.boot.loader.JarLauncher";
 		}
 
+		@Override
+		public String getLibraryLocation(String libraryName, LibraryScope scope) {
+			return "BOOT-INF/lib/";
+		}
+
+		@Deprecated
 		@Override
 		public String getLibraryDestination(String libraryName, LibraryScope scope) {
 			return "BOOT-INF/lib/";
@@ -123,25 +129,31 @@ public boolean isExecutable() {
 	 */
 	public static class War implements Layout {
 
-		private static final Map<LibraryScope, String> SCOPE_DESTINATIONS;
+		private static final Map<LibraryScope, String> SCOPE_LOCATION;
 
 		static {
-			Map<LibraryScope, String> map = new HashMap<>();
-			map.put(LibraryScope.COMPILE, "WEB-INF/lib/");
-			map.put(LibraryScope.CUSTOM, "WEB-INF/lib/");
-			map.put(LibraryScope.RUNTIME, "WEB-INF/lib/");
-			map.put(LibraryScope.PROVIDED, "WEB-INF/lib-provided/");
-			SCOPE_DESTINATIONS = Collections.unmodifiableMap(map);
+			Map<LibraryScope, String> locations = new HashMap<>();
+			locations.put(LibraryScope.COMPILE, "WEB-INF/lib/");
+			locations.put(LibraryScope.CUSTOM, "WEB-INF/lib/");
+			locations.put(LibraryScope.RUNTIME, "WEB-INF/lib/");
+			locations.put(LibraryScope.PROVIDED, "WEB-INF/lib-provided/");
+			SCOPE_LOCATION = Collections.unmodifiableMap(locations);
 		}
 
 		@Override
 		public String getLauncherClassName() {
 			return "org.springframework.boot.loader.WarLauncher";
 		}
 
+		@Override
+		public String getLibraryLocation(String libraryName, LibraryScope scope) {
+			return SCOPE_LOCATION.get(scope);
+		}
+
+		@Deprecated
 		@Override
 		public String getLibraryDestination(String libraryName, LibraryScope scope) {
-			return SCOPE_DESTINATIONS.get(scope);
+			return SCOPE_LOCATION.get(scope);
 		}
 
 		@Override