Support byte ranges in ResourceHttpRequestHandler

This commit introduces support for HTTP byte ranges in the
ResourceHttpRequestHandler. This support consists of a number of
changes:

- Parsing of HTTP Range headers in HttpHeaders, using a new HttpRange
  class and inner ByteRange/SuffixByteRange subclasses.
- MIME boundary generation moved from FormHttpMessageConverter to
  MimeTypeUtils.
- writePartialContent() method introduced in ResourceHttpRequestHandler,
  handling the byte range logic
- Additional partial content tests added to
  ResourceHttpRequestHandlerTests.

Issue: SPR-10805

spring-web/src/test/java/org/springframework/http/HttpHeadersTests.java

@@ -1,11 +1,11 @@
 /*
- * Copyright 2002-2014 the original author or authors.
+ * Copyright 2002-2015 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.
  * You may obtain a copy of the License at
  *
- *     http://www.apache.org/licenses/LICENSE-2.0
+ *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
@@ -30,11 +30,11 @@ import java.util.Locale;
 import java.util.TimeZone;
 
 import org.hamcrest.Matchers;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertThat;
 import org.junit.Before;
 import org.junit.Test;
 
-import static org.junit.Assert.*;
-
 /**
  * @author Arjen Poutsma
  */
@@ -266,4 +266,16 @@ public class HttpHeadersTests {
 		assertThat(headers.getAllow(), Matchers.emptyCollectionOf(HttpMethod.class));
 	}
 
+	@Test
+	public void range() {
+		List<HttpRange> ranges = new ArrayList<>();
+		ranges.add(HttpRange.createByteRange(0, 499));
+		ranges.add(HttpRange.createByteRange(9500));
+		ranges.add(HttpRange.createSuffixRange(500));
+
+		headers.setRange(ranges);
+		assertEquals("Invalid Range header", ranges, headers.getRange());
+		assertEquals("Invalid Range header", "bytes=0-499, 9500-, -500", headers.getFirst("Range"));
+	}
+
 }