Detect path of exploded war correctly on Windows

Previously, AbstractEmbeddedServletContainerFactory detected an
exploded war by looking for `/WEB-INF/` in the path of its code
source's location. This failed on Windows due to the use of `\` rather
than `/` separators.

This commit updates AbstractEmbeddedServletContainerFactory to
uses the OS's separator rather than hardcoding `/`.

Closes gh-8100

spring-boot/src/main/java/org/springframework/boot/context/embedded/AbstractEmbeddedServletContainerFactory.java

 /*
- * Copyright 2012-2015 the original author or authors.
+ * Copyright 2012-2017 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.
@@ -83,15 +83,21 @@ public abstract class AbstractEmbeddedServletContainerFactory
 	}
 
 	private File getExplodedWarFileDocumentRoot() {
-		File file = getCodeSourceArchive();
+		return getExplodedWarFileDocumentRoot(getCodeSourceArchive());
+	}
+
+	File getExplodedWarFileDocumentRoot(File codeSourceFile) {
 		if (this.logger.isDebugEnabled()) {
-			this.logger.debug("Code archive: " + file);
+			this.logger.debug("Code archive: " + codeSourceFile);
 		}
-		if (file != null && file.exists()
-				&& file.getAbsolutePath().contains("/WEB-INF/")) {
-			String path = file.getAbsolutePath();
-			path = path.substring(0, path.indexOf("/WEB-INF/"));
-			return new File(path);
+		if (codeSourceFile != null && codeSourceFile.exists()) {
+			String path = codeSourceFile.getAbsolutePath();
+			int webInfPathIndex = path
+					.indexOf(File.separatorChar + "WEB-INF" + File.separatorChar);
+			if (webInfPathIndex >= 0) {
+				path = path.substring(0, webInfPathIndex);
+				return new File(path);
+			}
 		}
 		return null;
 	}

spring-boot/src/test/java/org/springframework/boot/context/embedded/AbstractEmbeddedServletContainerFactoryTests.java

 /*
- * Copyright 2012-2016 the original author or authors.
+ * Copyright 2012-2017 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.
@@ -915,6 +915,24 @@ public abstract class AbstractEmbeddedServletContainerFactoryTests {
 		assertThat(getCharset(Locale.ITALIAN)).isNull();
 	}
 
+	@Test
+	public void explodedWarFileDocumentRootWhenRunningFromExplodedWar() throws Exception {
+		AbstractEmbeddedServletContainerFactory factory = getFactory();
+		File webInfClasses = this.temporaryFolder.newFolder("test.war", "WEB-INF", "lib",
+				"spring-boot.jar");
+		File documentRoot = factory.getExplodedWarFileDocumentRoot(webInfClasses);
+		assertThat(documentRoot)
+				.isEqualTo(webInfClasses.getParentFile().getParentFile().getParentFile());
+	}
+
+	@Test
+	public void explodedWarFileDocumentRootWhenRunningFromPackagedWar() throws Exception {
+		AbstractEmbeddedServletContainerFactory factory = getFactory();
+		File codeSourceFile = this.temporaryFolder.newFile("test.war");
+		File documentRoot = factory.getExplodedWarFileDocumentRoot(codeSourceFile);
+		assertThat(documentRoot).isNull();
+	}
+
 	protected abstract void addConnector(int port,
 			AbstractEmbeddedServletContainerFactory factory);