Propagate manifest to exploded jars

Update `LaunchedURLClassLoader` so that packages defined from exploded
archive folders have manifest attributes applied to them. Prior to this
calling `package.getImplementationTitle()` would only return the a
manifiest attribute when running non-exploded.

The root cause of this issue is the way that `URLClassLoader` handles
the different URL types. For URLs that reference a jar the manifest is
available. For URLs that reference a folder it isn't. When running
exploded we use a URL that references to the `BOOT-INF/classes` folder
directly. To fix the issue we now attempt to detect when `definePackage`
is being called directly, and replace `null` entries with actual
manifest values.

Fixes gh-21705

spring-boot-project/spring-boot-tools/spring-boot-loader/src/test/java/org/springframework/boot/loader/AbstractExecutableArchiveLauncherTests.java

@@ -33,6 +33,7 @@ import java.util.Set;
 import java.util.jar.JarEntry;
 import java.util.jar.JarFile;
 import java.util.jar.JarOutputStream;
+import java.util.jar.Manifest;
 import java.util.zip.CRC32;
 import java.util.zip.ZipEntry;
 
@@ -59,19 +60,31 @@ public abstract class AbstractExecutableArchiveLauncherTests {
 	@SuppressWarnings("resource")
 	protected File createJarArchive(String name, String entryPrefix, boolean indexed, List<String> extraLibs)
 			throws IOException {
+		return createJarArchive(name, null, entryPrefix, indexed, extraLibs);
+	}
+
+	@SuppressWarnings("resource")
+	protected File createJarArchive(String name, Manifest manifest, String entryPrefix, boolean indexed,
+			List<String> extraLibs) throws IOException {
 		File archive = new File(this.tempDir, name);
 		JarOutputStream jarOutputStream = new JarOutputStream(new FileOutputStream(archive));
+		if (manifest != null) {
+			jarOutputStream.putNextEntry(new JarEntry("META-INF/"));
+			jarOutputStream.putNextEntry(new JarEntry("META-INF/MANIFEST.MF"));
+			manifest.write(jarOutputStream);
+			jarOutputStream.closeEntry();
+		}
 		jarOutputStream.putNextEntry(new JarEntry(entryPrefix + "/"));
 		jarOutputStream.putNextEntry(new JarEntry(entryPrefix + "/classes/"));
 		jarOutputStream.putNextEntry(new JarEntry(entryPrefix + "/lib/"));
 		if (indexed) {
-			JarEntry indexEntry = new JarEntry(entryPrefix + "/classpath.idx");
-			jarOutputStream.putNextEntry(indexEntry);
+			jarOutputStream.putNextEntry(new JarEntry(entryPrefix + "/classpath.idx"));
 			Writer writer = new OutputStreamWriter(jarOutputStream, StandardCharsets.UTF_8);
 			writer.write("- \"BOOT-INF/lib/foo.jar\"\n");
 			writer.write("- \"BOOT-INF/lib/bar.jar\"\n");
 			writer.write("- \"BOOT-INF/lib/baz.jar\"\n");
 			writer.flush();
+			jarOutputStream.closeEntry();
 		}
 		addNestedJars(entryPrefix, "/lib/foo.jar", jarOutputStream);
 		addNestedJars(entryPrefix, "/lib/bar.jar", jarOutputStream);

spring-boot-project/spring-boot-tools/spring-boot-loader/src/test/java/org/springframework/boot/loader/JarLauncherTests.java

@@ -24,12 +24,17 @@ import java.util.Arrays;
 import java.util.Collections;
 import java.util.Iterator;
 import java.util.List;
+import java.util.jar.Attributes;
+import java.util.jar.Attributes.Name;
+import java.util.jar.Manifest;
 
 import org.junit.jupiter.api.Test;
 
 import org.springframework.boot.loader.archive.Archive;
 import org.springframework.boot.loader.archive.ExplodedArchive;
 import org.springframework.boot.loader.archive.JarFileArchive;
+import org.springframework.boot.testsupport.compiler.TestCompiler;
+import org.springframework.util.FileCopyUtils;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
@@ -95,6 +100,26 @@ class JarLauncherTests extends AbstractExecutableArchiveLauncherTests {
 		assertThat(urls).containsExactly(expectedFileUrls);
 	}
 
+	@Test
+	void explodedJarDefinedPackagesIncludeManifestAttributes() throws Exception {
+		Manifest manifest = new Manifest();
+		Attributes attributes = manifest.getMainAttributes();
+		attributes.put(Name.MANIFEST_VERSION, "1.0");
+		attributes.put(Name.IMPLEMENTATION_TITLE, "test");
+		File explodedRoot = explode(
+				createJarArchive("archive.jar", manifest, "BOOT-INF", true, Collections.emptyList()));
+		TestCompiler compiler = new TestCompiler(new File(explodedRoot, "BOOT-INF/classes"));
+		File source = new File(this.tempDir, "explodedsample/ExampleClass.java");
+		source.getParentFile().mkdirs();
+		FileCopyUtils.copy(new File("src/test/resources/explodedsample/ExampleClass.txt"), source);
+		compiler.getTask(Collections.singleton(source)).call();
+		JarLauncher launcher = new JarLauncher(new ExplodedArchive(explodedRoot, true));
+		Iterator<Archive> archives = launcher.getClassPathArchivesIterator();
+		URLClassLoader classLoader = (URLClassLoader) launcher.createClassLoader(archives);
+		Class<?> loaded = classLoader.loadClass("explodedsample.ExampleClass");
+		assertThat(loaded.getPackage().getImplementationTitle()).isEqualTo("test");
+	}
+
 	protected final URL[] getExpectedFileUrls(File explodedRoot) {
 		return getExpectedFiles(explodedRoot).stream().map(this::toUrl).toArray(URL[]::new);
 	}

spring-boot-project/spring-boot-tools/spring-boot-loader/src/test/resources/explodedsample/ExampleClass.txt

@@ -0,0 +1,26 @@
+/*
+ * 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.
+ * 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 explodedsample;
+
+/**
+ * Example class used to test class loading.
+ *
+ * @author Phillip Webb
+ */
+public class ExampleClass {
+
+}