Avoid expensive assertions in HttpRange

Closes gh-22742

spring-web/src/main/java/org/springframework/http/HttpRange.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2019 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.
@@ -68,18 +68,6 @@ public abstract class HttpRange {
 		return new ResourceRegion(resource, start, end - start + 1);
 	}
 
-	private static long getLengthFor(Resource resource) {
-		long contentLength;
-		try {
-			contentLength = resource.contentLength();
-			Assert.isTrue(contentLength > 0, "Resource content length should be > 0");
-		}
-		catch (IOException ex) {
-			throw new IllegalArgumentException("Failed to obtain Resource content length", ex);
-		}
-		return contentLength;
-	}
-
 	/**
 	 * Return the start of the range given the total length of a representation.
 	 * @param length the length of the representation
@@ -131,8 +119,8 @@ public abstract class HttpRange {
 	 * <p>This method can be used to parse an {@code Range} header.
 	 * @param ranges the string to parse
 	 * @return the list of ranges
-	 * @throws IllegalArgumentException if the string cannot be parsed, or if
-	 * the number of ranges is greater than 100.
+	 * @throws IllegalArgumentException if the string cannot be parsed
+	 * or if the number of ranges is greater than 100
 	 */
 	public static List<HttpRange> parseRanges(@Nullable String ranges) {
 		if (!StringUtils.hasLength(ranges)) {
@@ -144,7 +132,9 @@ public abstract class HttpRange {
 		ranges = ranges.substring(BYTE_RANGE_PREFIX.length());
 
 		String[] tokens = StringUtils.tokenizeToStringArray(ranges, ",");
-		Assert.isTrue(tokens.length <= MAX_RANGES, () -> "Too many ranges " + tokens.length);
+		if (tokens.length > MAX_RANGES) {
+			throw new IllegalArgumentException("Too many ranges: " + tokens.length);
+		}
 		List<HttpRange> result = new ArrayList<>(tokens.length);
 		for (String token : tokens) {
 			result.add(parseRange(token));
@@ -158,7 +148,7 @@ public abstract class HttpRange {
 		if (dashIdx > 0) {
 			long firstPos = Long.parseLong(range.substring(0, dashIdx));
 			if (dashIdx < range.length() - 1) {
-				Long lastPos = Long.parseLong(range.substring(dashIdx + 1, range.length()));
+				Long lastPos = Long.parseLong(range.substring(dashIdx + 1));
 				return new ByteRange(firstPos, lastPos);
 			}
 			else {
@@ -195,13 +185,25 @@ public abstract class HttpRange {
 		if (ranges.size() > 1) {
 			long length = getLengthFor(resource);
 			long total = regions.stream().map(ResourceRegion::getCount).reduce(0L, (count, sum) -> sum + count);
-			Assert.isTrue(total < length,
-					() -> "The sum of all ranges (" + total + ") " +
-							"should be less than the resource length (" + length + ")");
+			if (total >= length) {
+				throw new IllegalArgumentException("The sum of all ranges (" + total +
+						") should be less than the resource length (" + length + ")");
+			}
 		}
 		return regions;
 	}
 
+	private static long getLengthFor(Resource resource) {
+		try {
+			long contentLength = resource.contentLength();
+			Assert.isTrue(contentLength > 0, "Resource content length should be > 0");
+			return contentLength;
+		}
+		catch (IOException ex) {
+			throw new IllegalArgumentException("Failed to obtain Resource content length", ex);
+		}
+	}
+
 	/**
 	 * Return a string representation of the given list of {@code HttpRange} objects.
 	 * <p>This method can be used to for an {@code Range} header.

spring-web/src/main/java/org/springframework/http/codec/ResourceHttpMessageWriter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2019 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.
@@ -53,9 +53,8 @@ import org.springframework.util.MimeTypeUtils;
 /**
  * {@code HttpMessageWriter} that can write a {@link Resource}.
  *
- * <p>Also an implementation of {@code HttpMessageWriter} with support
- * for writing one or more {@link ResourceRegion}'s based on the HTTP ranges
- * specified in the request.
+ * <p>Also an implementation of {@code HttpMessageWriter} with support for writing one
+ * or more {@link ResourceRegion}'s based on the HTTP ranges specified in the request.
  *
  * <p>For reading to a Resource, use {@link ResourceDecoder} wrapped with
  * {@link DecoderHttpMessageReader}.
@@ -187,7 +186,6 @@ public class ResourceHttpMessageWriter implements HttpMessageWriter<Resource> {
 	// Server-side only: single Resource or sub-regions...
 
 	@Override
-	@SuppressWarnings("unchecked")
 	public Mono<Void> write(Publisher<? extends Resource> inputStream, @Nullable ResolvableType actualType,
 			ResolvableType elementType, @Nullable MediaType mediaType, ServerHttpRequest request,
 			ServerHttpResponse response, Map<String, Object> hints) {
@@ -205,15 +203,12 @@ public class ResourceHttpMessageWriter implements HttpMessageWriter<Resource> {
 		}
 
 		return Mono.from(inputStream).flatMap(resource -> {
-
 			if (ranges.isEmpty()) {
 				return writeResource(resource, elementType, mediaType, response, hints);
 			}
-
 			response.setStatusCode(HttpStatus.PARTIAL_CONTENT);
 			List<ResourceRegion> regions = HttpRange.toResourceRegions(ranges, resource);
 			MediaType resourceMediaType = getResourceMediaType(mediaType, resource, hints);
-
 			if (regions.size() == 1){
 				ResourceRegion region = regions.get(0);
 				headers.setContentType(resourceMediaType);