Add support for artifacts without version numbers

Author: jjelliott

launcher/src/main/java/org/springframework/boot/loader/thin/PathResolver.java

@@ -140,14 +140,18 @@ public Resource getPom(Archive archive) {
 				throw new IllegalStateException("Cannot locate archive", e);
 			}
 			String pattern = "META-INF/maven/**"
-					+ (artifactId == null ? "" : "/" + artifactId) + "/pom.xml";
+					+ (artifactId == null || artifactId.length() == 0 ? ""
+							: "/" + artifactId)
+					+ "/pom.xml";
 			Resource resource = findResource(archive, pattern);
 			if (resource != null) {
 				return resource;
 			}
 			// Spring Boot fat jar
 			pattern = "BOOT-INF/classes/META-INF/maven/**"
-					+ (artifactId == null ? "" : "/" + artifactId) + "/pom.xml";
+					+ (artifactId == null || artifactId.length() == 0 ? ""
+							: "/" + artifactId)
+					+ "/pom.xml";
 			resource = findResource(archive, pattern);
 			if (resource != null) {
 				return resource;
@@ -399,6 +403,7 @@ private String extractArtifactId(Archive archive) throws MalformedURLException {
 			path = path.substring(0, path.length() - 2);
 		}
 		path = StringUtils.getFilename(path);
+		path = path.replace(".jar", "");
 		path = path.split("-[0-9]")[0];
 		return path;
 	}

launcher/src/test/java/org/springframework/boot/loader/thin/PathResolverTests.java

@@ -135,4 +135,12 @@ public void pomWithMavenArchiveBootInf() throws Exception {
 				"BOOT-INF/classes/META-INF/maven/org.springframework.boot/spring-boot-cli/pom.xml");
 	}
 
+	@Test
+	public void pomWithUnversionedJar() throws Exception {
+		Resource resource = resolver.getPom(
+				new ExplodedArchive(new File("src/test/resources/apps/fake.jar")));
+		assertThat(resource.getURL().toString())
+				.endsWith("META-INF/maven/com.example/fake/pom.xml");
+	}
+
 }

launcher/src/test/resources/apps/fake.jar/META-INF/maven/com.example/fake/pom.xml

@@ -0,0 +1,14 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
+	<modelVersion>4.0.0</modelVersion>
+
+	<groupId>com.example</groupId>
+	<artifactId>simple</artifactId>
+	<version>0.0.1-SNAPSHOT</version>
+	<packaging>jar</packaging>
+
+	<name>simple</name>
+	<description>Demo project for Spring Boot</description>
+
+</project>