Use X-Forwarded-Prefix in ServletUriComponentsBuilder

Issue: SPR-12500

Author: rstoyanchev

spring-webmvc/src/main/java/org/springframework/web/servlet/support/ServletUriComponentsBuilder.java

@@ -35,7 +35,7 @@
  */
 public class ServletUriComponentsBuilder extends UriComponentsBuilder {
 
-	private String servletRequestURI;
+	private String originalPath;
 
 
 	/**
@@ -86,7 +86,6 @@ public static ServletUriComponentsBuilder fromServletMapping(HttpServletRequest
 	 */
 	public static ServletUriComponentsBuilder fromRequestUri(HttpServletRequest request) {
 		ServletUriComponentsBuilder builder = fromRequest(request);
-		builder.pathFromRequest(request);
 		builder.replaceQuery(null);
 		return builder;
 	}
@@ -99,6 +98,7 @@ public static ServletUriComponentsBuilder fromRequest(HttpServletRequest request
 		String scheme = request.getScheme();
 		String host = request.getServerName();
 		int port = request.getServerPort();
+		String path = request.getRequestURI();
 
 		String hostHeader = request.getHeader("X-Forwarded-Host");
 		if (StringUtils.hasText(hostHeader)) {
@@ -125,13 +125,18 @@ public static ServletUriComponentsBuilder fromRequest(HttpServletRequest request
 			scheme = protocolHeader;
 		}
 
+		String prefix = request.getHeader("X-Forwarded-Prefix");
+		if (StringUtils.hasText(prefix)) {
+			path = prefix + path;
+		}
+
 		ServletUriComponentsBuilder builder = new ServletUriComponentsBuilder();
 		builder.scheme(scheme);
 		builder.host(host);
 		if (scheme.equals("http") && port != 80 || scheme.equals("https") && port != 443) {
 			builder.port(port);
 		}
-		builder.pathFromRequest(request);
+		builder.initPath(path);
 		builder.query(request.getQueryString());
 		return builder;
 	}
@@ -180,37 +185,37 @@ protected static HttpServletRequest getCurrentRequest() {
 		return servletRequest;
 	}
 
-	private void pathFromRequest(HttpServletRequest request) {
-		this.servletRequestURI = request.getRequestURI();
-		replacePath(request.getRequestURI());
+	private void initPath(String path) {
+		this.originalPath = path;
+		replacePath(path);
 	}
 
 	/**
 	 * Removes any path extension from the {@link HttpServletRequest#getRequestURI()
 	 * requestURI}. This method must be invoked before any calls to {@link #path(String)}
 	 * or {@link #pathSegment(String...)}.
 	 * <pre>
-	 * 	// GET http://foo.com/rest/books/6.json
 	 *
-	 *	ServletUriComponentsBuilder builder = ServletUriComponentsBuilder.fromRequestUri(this.request);
-	 *	String ext = builder.removePathExtension();
-	 *	String uri = builder.path("/pages/1.{ext}").buildAndExpand(ext).toUriString();
+	 * GET http://foo.com/rest/books/6.json
 	 *
-	 * 	assertEquals("http://foo.com/rest/books/6/pages/1.json", result);
+	 * ServletUriComponentsBuilder builder = ServletUriComponentsBuilder.fromRequestUri(this.request);
+	 * String ext = builder.removePathExtension();
+	 * String uri = builder.path("/pages/1.{ext}").buildAndExpand(ext).toUriString();
+	 * assertEquals("http://foo.com/rest/books/6/pages/1.json", result);
 	 * </pre>
 	 * @return the removed path extension for possible re-use, or {@code null}
 	 * @since 4.0
 	 */
 	public String removePathExtension() {
 		String extension = null;
-		if (this.servletRequestURI != null) {
-			String filename = WebUtils.extractFullFilenameFromUrlPath(this.servletRequestURI);
+		if (this.originalPath != null) {
+			String filename = WebUtils.extractFullFilenameFromUrlPath(this.originalPath);
 			extension = StringUtils.getFilenameExtension(filename);
 			if (!StringUtils.isEmpty(extension)) {
-				int end = this.servletRequestURI.length() - (extension.length() + 1);
-				replacePath(this.servletRequestURI.substring(0, end));
+				int end = this.originalPath.length() - (extension.length() + 1);
+				replacePath(this.originalPath.substring(0, end));
 			}
-			this.servletRequestURI = null;
+			this.originalPath = null;
 		}
 		return extension;
 	}

spring-webmvc/src/test/java/org/springframework/web/servlet/support/ServletUriComponentsBuilderTests.java

@@ -150,6 +150,24 @@ public void fromRequestWithForwardedHostWithForwardedScheme() {
 		assertEquals("should have used the default port of the forwarded request", -1, result.getPort());
 	}
 
+	@Test
+	public void fromRequestWithForwardedPrefix() {
+		this.request.setRequestURI("/bar");
+		this.request.addHeader("X-Forwarded-Prefix", "/foo");
+		UriComponents result = ServletUriComponentsBuilder.fromRequest(request).build();
+
+		assertEquals("http://localhost/foo/bar", result.toUriString());
+	}
+
+	@Test
+	public void fromRequestWithForwardedPrefixTrailingSlash() {
+		this.request.setRequestURI("/bar");
+		this.request.addHeader("X-Forwarded-Prefix", "/foo/");
+		UriComponents result = ServletUriComponentsBuilder.fromRequest(request).build();
+
+		assertEquals("http://localhost/foo/bar", result.toUriString());
+	}
+
 	@Test
 	public void fromContextPath() {
 		request.setRequestURI("/mvc-showcase/data/param");