Polish "Determine Spring Boot version correctly when using module path"

See gh-16182

Author: wilkinsona

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/SpringBootVersion.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2018 the original author or authors.
+ * Copyright 2012-2019 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.
@@ -22,18 +22,23 @@
 import java.net.URL;
 import java.net.URLConnection;
 import java.util.jar.Attributes;
+import java.util.jar.Attributes.Name;
 import java.util.jar.JarFile;
 
 /**
- * Class that exposes the Spring Boot version. Fetches the "Implementation-Version"
- * manifest attribute from the jar file.
+ * Class that exposes the Spring Boot version. Fetches the
+ * {@link Name#IMPLEMENTATION_VERSION Implementation-Version} manifest attribute from the
+ * jar file via {@link Package#getImplementationVersion()}, falling back to locating the
+ * jar file that contains this class and reading the {@code Implementation-Version}
+ * attribute from its manifest.
  * <p>
- * Note that some ClassLoaders do not expose the package metadata, hence this class might
- * not be able to determine the Spring Boot version in all environments. Consider using a
- * reflection-based check instead: For example, checking for the presence of a specific
- * Spring Boot method that you intend to call.
+ * This class might not be able to determine the Spring Boot version in all environments.
+ * Consider using a reflection-based check instead: For example, checking for the presence
+ * of a specific Spring Boot method that you intend to call.
  *
  * @author Drummond Dawson
+ * @author Hendrig Sellik
+ * @author Andy Wilkinson
  * @since 1.3.0
  */
 public final class SpringBootVersion {