Improve illegal MimeType checks

Issue: SPR-14124

spring-core/src/main/java/org/springframework/util/MimeTypeUtils.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2016 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.
@@ -220,6 +220,9 @@ public abstract class MimeTypeUtils {
 			throw new InvalidMimeTypeException(mimeType, "'mimeType' must not be empty");
 		}
 		String[] parts = StringUtils.tokenizeToStringArray(mimeType, ";");
+		if (parts.length == 0) {
+			throw new InvalidMimeTypeException(mimeType, "'mimeType' must not be empty");
+		}
 
 		String fullType = parts[0].trim();
 		// java.net.HttpURLConnection returns a *; q=.2 Accept header

spring-core/src/test/java/org/springframework/util/MimeTypeTests.java

@@ -189,6 +189,11 @@ public class MimeTypeTests {
 		MimeTypeUtils.parseMimeType("audio/basic)");
 	}
 
+	@Test(expected = InvalidMimeTypeException.class)
+	public void parseMimeTypeMissingTypeAndSubtype() throws Exception {
+		MimeTypeUtils.parseMimeType("     ;a=b");
+	}
+
 	@Test(expected = InvalidMimeTypeException.class)
 	public void parseMimeTypeEmptyParameterAttribute() {
 		MimeTypeUtils.parseMimeType("audio/*;=value");
@@ -263,13 +268,13 @@ public class MimeTypeTests {
 
 		assertTrue("Invalid comparison result", audioBasicLevel.compareTo(audio) > 0);
 
-		List<MimeType> expected = new ArrayList<MimeType>();
+		List<MimeType> expected = new ArrayList<>();
 		expected.add(audio);
 		expected.add(audioBasic);
 		expected.add(audioBasicLevel);
 		expected.add(audioWave);
 
-		List<MimeType> result = new ArrayList<MimeType>(expected);
+		List<MimeType> result = new ArrayList<>(expected);
 		Random rnd = new Random();
 		// shuffle & sort 10 times
 		for (int i = 0; i < 10; i++) {