Support nested jar paths in loader.path

See gh-11121

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

@@ -483,6 +483,10 @@ public class PropertiesLauncher extends Launcher {
 	}
 
 	private Archive getArchive(File file) throws IOException {
+		// Nested path never exists as plain jar file, which should be ignored here.
+		if (file.getPath().contains("!")) {
+			return null;
+		}
 		String name = file.getName().toLowerCase();
 		if (name.endsWith(".jar") || name.endsWith(".zip")) {
 			return new JarFileArchive(file);

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

@@ -213,6 +213,15 @@ public class PropertiesLauncherTests {
 		assertThat(archives).areExactly(1, endingWith("app.jar!/"));
 	}
 
+	@Test
+	public void testUserSpecifiedNestedJarPath() throws Exception {
+		System.setProperty("loader.path", "nested-jars/app.jar!/foo.jar");
+		System.setProperty("loader.main", "demo.Application");
+		PropertiesLauncher launcher = new PropertiesLauncher();
+		List<Archive> archives = launcher.getClassPathArchives();
+		assertThat(archives).hasSize(1).areExactly(1, endingWith("foo.jar!/"));
+	}
+
 	@Test
 	public void testUserSpecifiedDirectoryContainingJarFileWithNestedArchives()
 			throws Exception {