Support comma-separated X-Forwarded-Port

Issue: SPR-12813

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

@@ -297,7 +297,8 @@ public class UriComponentsBuilder implements Cloneable {
 
 		String portHeader = request.getHeaders().getFirst("X-Forwarded-Port");
 		if (StringUtils.hasText(portHeader)) {
-			port = Integer.parseInt(portHeader);
+			String[] ports = StringUtils.commaDelimitedListToStringArray(portHeader);
+			port = Integer.parseInt(ports[0]);
 		}
 
 		String protocolHeader = request.getHeaders().getFirst("X-Forwarded-Proto");

spring-web/src/test/java/org/springframework/web/util/UriComponentsBuilderTests.java

@@ -399,8 +399,23 @@ public class UriComponentsBuilderTests {
 		assertEquals("https://84.198.58.199/mvc-showcase", result.toString());
 	}
 
+	// SPR-12813
 
+	@Test
+	public void fromHttpRequestWithForwardedPortMultiValueHeader() {
+		MockHttpServletRequest request = new MockHttpServletRequest();
+		request.setScheme("http");
+		request.setServerName("localhost");
+		request.setServerPort(9090);
+		request.setRequestURI("/mvc-showcase");
+		request.addHeader("X-Forwarded-Host", "a.example.org");
+		request.addHeader("X-Forwarded-Port", "80,52022");
 
+		HttpRequest httpRequest = new ServletServerHttpRequest(request);
+		UriComponents result = UriComponentsBuilder.fromHttpRequest(httpRequest).build();
+
+		assertEquals("http://a.example.org/mvc-showcase", result.toString());
+	}
 
 	@Test
 	public void path() throws URISyntaxException {