Support contextPath override in ForwardedHeaderFilter

Issue: SPR-13614

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

@@ -31,9 +31,11 @@ import javax.servlet.http.HttpServletResponse;
 
 import org.springframework.http.HttpRequest;
 import org.springframework.http.server.ServletServerHttpRequest;
+import org.springframework.util.Assert;
 import org.springframework.util.CollectionUtils;
 import org.springframework.web.util.UriComponents;
 import org.springframework.web.util.UriComponentsBuilder;
+import org.springframework.web.util.UrlPathHelper;
 
 
 /**
@@ -61,6 +63,28 @@ public class ForwardedHeaderFilter extends OncePerRequestFilter {
 	}
 
 
+	private ContextPathHelper contextPathHelper;
+
+
+
+	/**
+	 * Configure a contextPath value that will replace the contextPath of
+	 * proxy-forwarded requests.
+	 *
+	 * <p>This is useful when external clients are not aware of the application
+	 * context path. However a proxy forwards the request to a URL that includes
+	 * a contextPath.
+	 *
+	 * @param contextPath the context path; the given value will be sanitized to
+	 * ensure it starts with a '/' but does not end with one, or if the context
+	 * path is empty (default, root context) it is left as-is.
+	 */
+	public void setContextPath(String contextPath) {
+		Assert.notNull(contextPath, "'contextPath' must not be null");
+		this.contextPathHelper = new ContextPathHelper(contextPath);
+	}
+
+
 	@Override
 	protected boolean shouldNotFilter(HttpServletRequest request) throws ServletException {
 		Enumeration<String> headerNames = request.getHeaderNames();
@@ -87,7 +111,7 @@ public class ForwardedHeaderFilter extends OncePerRequestFilter {
 	protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response,
 			FilterChain filterChain) throws ServletException, IOException {
 
-		filterChain.doFilter(new ForwardedHeaderRequestWrapper(request), response);
+		filterChain.doFilter(new ForwardedHeaderRequestWrapper(request, this.contextPathHelper), response);
 	}
 
 
@@ -105,12 +129,16 @@ public class ForwardedHeaderFilter extends OncePerRequestFilter {
 
 		private final int port;
 
+		private final String contextPath;
+
+		private final String requestUri;
+
 		private final StringBuffer requestUrl;
 
 		private final Map<String, List<String>> headers;
 
 
-		public ForwardedHeaderRequestWrapper(HttpServletRequest request) {
+		public ForwardedHeaderRequestWrapper(HttpServletRequest request, ContextPathHelper pathHelper) {
 			super(request);
 
 			HttpRequest httpRequest = new ServletServerHttpRequest(request);
@@ -121,7 +149,11 @@ public class ForwardedHeaderFilter extends OncePerRequestFilter {
 			this.secure = "https".equals(scheme);
 			this.host = uriComponents.getHost();
 			this.port = (port == -1 ? (this.secure ? 443 : 80) : port);
-			this.requestUrl = initRequestUrl(this.scheme, this.host, port, request.getRequestURI());
+
+			this.contextPath = (pathHelper != null ? pathHelper.getContextPath(request) : request.getContextPath());
+			this.requestUri = (pathHelper != null ? pathHelper.getRequestUri(request) : request.getRequestURI());
+			this.requestUrl = initRequestUrl(this.scheme, this.host, port, this.requestUri);
+
 			this.headers = initHeaders(request);
 		}
 
@@ -170,6 +202,16 @@ public class ForwardedHeaderFilter extends OncePerRequestFilter {
 			return this.secure;
 		}
 
+		@Override
+		public String getContextPath() {
+			return this.contextPath;
+		}
+
+		@Override
+		public String getRequestURI() {
+			return this.requestUri;
+		}
+
 		@Override
 		public StringBuffer getRequestURL() {
 			return this.requestUrl;
@@ -195,4 +237,50 @@ public class ForwardedHeaderFilter extends OncePerRequestFilter {
 		}
 	}
 
+
+	private static class ContextPathHelper {
+
+		private final String contextPath;
+
+		private final UrlPathHelper urlPathHelper;
+
+
+		public ContextPathHelper(String contextPath) {
+			Assert.notNull(contextPath);
+			this.contextPath = sanitizeContextPath(contextPath);
+			this.urlPathHelper = new UrlPathHelper();
+			this.urlPathHelper.setUrlDecode(false);
+			this.urlPathHelper.setRemoveSemicolonContent(false);
+		}
+
+		private static String sanitizeContextPath(String contextPath) {
+			contextPath = contextPath.trim();
+			if (contextPath.isEmpty()) {
+				return contextPath;
+			}
+			if (contextPath.equals("/")) {
+				return "/";
+			}
+			if (contextPath.charAt(0) != '/') {
+				contextPath = "/"  + contextPath;
+			}
+			while (contextPath.endsWith("/")) {
+				contextPath = contextPath.substring(0, contextPath.length() -1);
+			}
+			return contextPath;
+		}
+
+		public String getContextPath(HttpServletRequest request) {
+			return this.contextPath;
+		}
+
+		public String getRequestUri(HttpServletRequest request) {
+			String pathWithinApplication = this.urlPathHelper.getPathWithinApplication(request);
+			if (this.contextPath.equals("/") && pathWithinApplication.startsWith("/")) {
+				return pathWithinApplication;
+			}
+			return this.contextPath + pathWithinApplication;
+		}
+	}
+
 }