Allow PropertyLauncher loader.path to be configured using manifest

Closes gh-7178

spring-boot-docs/src/main/asciidoc/appendix-executable-jar-format.adoc

@@ -200,12 +200,12 @@ the appropriate launcher:
 properties (System properties, environment variables, manifest entries or
 `application.properties`).
 
-[cols="2,4"]
 |===
 |Key |Purpose
 
 |`loader.path`
-|Comma-separated Classpath, e.g. `lib,${HOME}/app/lib`. Earlier entries take precedence, just like a regular `-classpath` on the `javac` command line.
+|Comma-separated Classpath, e.g. `lib,${HOME}/app/lib`. Earlier entries take precedence,
+ just like a regular `-classpath` on the `javac` command line.
 
 |`loader.home`
 |Location of additional properties file, e.g. `file:///opt/app`
@@ -227,25 +227,52 @@ properties (System properties, environment variables, manifest entries or
 |`loader.system`
 |Boolean flag to indicate that all properties should be added to System properties
  (defaults to `false`)
+
 |===
 
-Manifest entry keys are formed by capitalizing initial letters of words and changing the
-separator to "`-`" from "`.`" (e.g. `Loader-Path`). The exception is `loader.main` which
-is looked up as `Start-Class` in the manifest for compatibility with `JarLauncher`).
+When specified as environment variables or manifest entries, the following names should
+be used:
+
+|===
+|Key | Manifest entry | Environment variable
+
+|`loader.path`
+|`Loader-Path`
+|`LOADER_PATH`
+
+|`loader.home`
+|
+|`LOADER_HOME`
+
+|`loader.args`
+|`Loader-Args`
+|`LOADER_ARGS`
+
+|`loader.main`
+|`Start-Class`
+|`LOADER_MAIN`
+
+|`loader.config.location`
+|
+|`LOADER_CONFIG_LOCATION`
+
+|`loader.system`
+|
+|`LOADER_SYSTEM`
+
+|===
 
 TIP: Build plugins automatically move the `Main-Class` attribute to `Start-Class` when
 the fat jar is built. If you are using that, specify the name of the class to launch using
 the `Main-Class` attribute and leave out `Start-Class`.
 
-Environment variables can be capitalized with underscore separators instead of periods.
-
 * `loader.home` is the directory location of an additional properties file (overriding
-  the default) as long as `loader.config.location` is   not specified.
+  the default) as long as `loader.config.location` is not specified.
 * `loader.path` can contain directories (scanned recursively for jar and zip files),
   archive paths, or wildcard patterns (for the default JVM behavior).
-* `loader.path` (if empty) defaults to `lib` (meaning a local directory or a nested one if
-  running from an archive). Because of this `PropertiesLauncher` behaves the same as
-  `JarLauncher` when no additional configuration is provided.
+* `loader.path` (if empty) defaults to `BOOT-INF/lib` (meaning a local directory or a
+  nested one if running from an archive). Because of this `PropertiesLauncher` behaves the
+  same as `JarLauncher` when no additional configuration is provided.
 * Placeholder replacement is done from System and environment variables plus the
   properties file itself on all values before use.
 

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

@@ -132,7 +132,7 @@ public class PropertiesLauncher extends Launcher {
 	public PropertiesLauncher() {
 		try {
 			this.home = getHomeDirectory();
-			initializeProperties(this.home);
+			initializeProperties();
 			initializePaths();
 			this.parent = createArchive();
 		}
@@ -146,7 +146,7 @@ public class PropertiesLauncher extends Launcher {
 				.resolvePlaceholders(System.getProperty(HOME, "${user.dir}")));
 	}
 
-	private void initializeProperties(File home) throws Exception, IOException {
+	private void initializeProperties() throws Exception, IOException {
 		String config = "classpath:BOOT-INF/classes/"
 				+ SystemPropertyUtils.resolvePlaceholders(
 						SystemPropertyUtils.getProperty(CONFIG_NAME, "application"))
@@ -273,14 +273,10 @@ public class PropertiesLauncher extends Launcher {
 		}
 	}
 
-	private void initializePaths() throws IOException {
-		String path = SystemPropertyUtils.getProperty(PATH);
-		if (path == null) {
-			path = this.properties.getProperty(PATH);
-		}
+	private void initializePaths() throws Exception {
+		String path = getProperty(PATH);
 		if (path != null) {
-			this.paths = parsePathsProperty(
-					SystemPropertyUtils.resolvePlaceholders(path));
+			this.paths = parsePathsProperty(path);
 		}
 		log("Nested archive paths: " + this.paths);
 	}

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

@@ -17,16 +17,21 @@
 package org.springframework.boot.loader;
 
 import java.io.File;
+import java.io.FileOutputStream;
 import java.io.IOException;
 import java.net.URL;
 import java.net.URLClassLoader;
 import java.util.Arrays;
 import java.util.Collections;
+import java.util.List;
+import java.util.jar.Attributes;
+import java.util.jar.Manifest;
 
 import org.junit.After;
 import org.junit.Before;
 import org.junit.Rule;
 import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
 import org.mockito.MockitoAnnotations;
 
 import org.springframework.boot.loader.archive.Archive;
@@ -45,6 +50,9 @@ public class PropertiesLauncherTests {
 	@Rule
 	public InternalOutputCapture output = new InternalOutputCapture();
 
+	@Rule
+	public TemporaryFolder temporaryFolder = new TemporaryFolder();
+
 	@Before
 	public void setup() throws IOException {
 		MockitoAnnotations.initMocks(this);
@@ -207,6 +215,23 @@ public class PropertiesLauncherTests {
 				.isEqualTo("[foo, bar]");
 	}
 
+	@SuppressWarnings("unchecked")
+	@Test
+	public void testLoadPathCustomizedUsingManifest() throws Exception {
+		System.setProperty("loader.home",
+				this.temporaryFolder.getRoot().getAbsolutePath());
+		Manifest manifest = new Manifest();
+		manifest.getMainAttributes().put(Attributes.Name.MANIFEST_VERSION, "1.0");
+		manifest.getMainAttributes().putValue("Loader-Path", "/foo.jar, /bar");
+		File manifestFile = new File(this.temporaryFolder.getRoot(),
+				"META-INF/MANIFEST.MF");
+		manifestFile.getParentFile().mkdirs();
+		manifest.write(new FileOutputStream(manifestFile));
+		PropertiesLauncher launcher = new PropertiesLauncher();
+		assertThat((List<String>) ReflectionTestUtils.getField(launcher, "paths"))
+				.containsExactly("/foo.jar", "/bar/");
+	}
+
 	private void waitFor(String value) throws Exception {
 		int count = 0;
 		boolean timeout = false;

spring-boot-tools/spring-boot-loader/src/test/resources/BOOT-INF/classes/application.properties

 loader.main: demo.Application
-loader.path: etc/,lib,.