Replaces rather than prepend contextPath

Issue: SPR-16650

spring-web/src/main/java/org/springframework/web/util/UriComponentsBuilder.java

@@ -724,6 +724,11 @@ public class UriComponentsBuilder implements UriBuilder, Cloneable {
 	 * "Forwarded" (<a href="http://tools.ietf.org/html/rfc7239">RFC 7239</a>,
 	 * or "X-Forwarded-Host", "X-Forwarded-Port", and "X-Forwarded-Proto" if
 	 * "Forwarded" is not found.
+	 * <p><strong>Note:</strong> this method uses values from forwarded headers,
+	 * if present, in order to reflect the client-originated protocol and address.
+	 * Consider using the {@code ForwardedHeaderFilter} in order to choose from a
+	 * central place whether to extract and use, or to discard such headers.
+	 * See the Spring Framework reference for more on this filter.
 	 * @param headers the HTTP headers to consider
 	 * @return this UriComponentsBuilder
 	 * @since 4.2.7