Fixed generateETagHeaderValue's IOException handling

Issue: SPR-12081

spring-web/src/main/java/org/springframework/web/filter/ShallowEtagHeaderFilter.java

@@ -163,14 +163,9 @@ public class ShallowEtagHeaderFilter extends OncePerRequestFilter {
 	 * @return the ETag header value
 	 * @see org.springframework.util.DigestUtils
 	 */
-	protected String generateETagHeaderValue(InputStream inputStream) {
+	protected String generateETagHeaderValue(InputStream inputStream) throws IOException {
 		StringBuilder builder = new StringBuilder("\"0");
-		try {
-			DigestUtils.appendMd5DigestAsHex(inputStream, builder);
-		}
-		catch (IOException e) {
-			throw new RuntimeException(e);
-		}
+		DigestUtils.appendMd5DigestAsHex(inputStream, builder);
 		builder.append('"');
 		return builder.toString();
 	}
@@ -184,7 +179,7 @@ public class ShallowEtagHeaderFilter extends OncePerRequestFilter {
 	 * @since 4.2
 	 */
 	public static void disableContentCaching(ServletRequest request) {
-		Assert.notNull(request);
+		Assert.notNull(request, "ServletRequest must not be null");
 		request.setAttribute(STREAMING_ATTRIBUTE, true);
 	}