Polish

See gh-24597

spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/main/java/org/springframework/boot/maven/JarTypeFilter.java

 /*
- * Copyright 2012-2020 the original author or authors.
+ * Copyright 2012-2021 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.
@@ -20,7 +20,6 @@ import java.io.IOException;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.HashSet;
-import java.util.Optional;
 import java.util.Set;
 import java.util.jar.JarFile;
 import java.util.jar.Manifest;
@@ -45,13 +44,18 @@ class JarTypeFilter extends DependencyFilter {
 	@Override
 	protected boolean filter(Artifact artifact) {
 		try (JarFile jarFile = new JarFile(artifact.getFile())) {
-			return Optional.ofNullable(jarFile.getManifest()).map(Manifest::getMainAttributes)
-					.map((attributes) -> attributes.getValue("Spring-Boot-Jar-Type")).map(EXCLUDED_JAR_TYPES::contains)
-					.orElse(Boolean.FALSE);
+			Manifest manifest = jarFile.getManifest();
+			if (manifest != null) {
+				String jarType = manifest.getMainAttributes().getValue("Spring-Boot-Jar-Type");
+				if (jarType != null && EXCLUDED_JAR_TYPES.contains(jarType)) {
+					return true;
+				}
+			}
 		}
 		catch (IOException ex) {
-			return false;
+			// Continue
 		}
+		return false;
 	}
 
 }