Add ForwardedHeaderFilter

The new Filter is simply a new way of packaging the ability to extract
X-Forwarded-* headers already available via UriComponentsBuilder.

The Filter wraps the request and the effect is that anything using the
request will see the original schem, host, and port.

Issue: SPR-13614

spring-web/src/test/java/org/springframework/web/filter/ForwardedHeaderFilterTests.java

@@ -0,0 +1,92 @@
+/*
+ * Copyright 2002-2016 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.web.filter;
+
+import javax.servlet.ServletException;
+import javax.servlet.http.HttpServlet;
+import javax.servlet.http.HttpServletRequest;
+
+import org.junit.Test;
+
+import org.springframework.mock.web.test.MockFilterChain;
+import org.springframework.mock.web.test.MockHttpServletRequest;
+import org.springframework.mock.web.test.MockHttpServletResponse;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertTrue;
+
+/**
+ * Unit tests for {@link ForwardedHeaderFilter}.
+ * @author Rossen Stoyanchev
+ */
+public class ForwardedHeaderFilterTests {
+
+	private final ForwardedHeaderFilter filter = new ForwardedHeaderFilter();
+
+
+	@Test
+	public void shouldFilter() throws Exception {
+		testShouldFilter("Forwarded");
+		testShouldFilter("X-Forwarded-Host");
+		testShouldFilter("X-Forwarded-Port");
+		testShouldFilter("X-Forwarded-Proto");
+	}
+
+	@Test
+	public void shouldNotFilter() throws Exception {
+		assertTrue(this.filter.shouldNotFilter(new MockHttpServletRequest()));
+	}
+
+	@Test
+	public void xForwardedHeaders() throws Exception {
+		MockHttpServletRequest request = new MockHttpServletRequest();
+		request.setScheme("http");
+		request.setServerName("localhost");
+		request.setServerPort(80);
+		request.setRequestURI("/mvc-showcase");
+		request.addHeader("X-Forwarded-Proto", "https");
+		request.addHeader("X-Forwarded-Host", "84.198.58.199");
+		request.addHeader("X-Forwarded-Port", "443");
+		request.addHeader("foo", "bar");
+
+		MockFilterChain chain = new MockFilterChain(new HttpServlet() {});
+
+		this.filter.doFilter(request, new MockHttpServletResponse(), chain);
+
+		HttpServletRequest actual = (HttpServletRequest) chain.getRequest();
+		assertEquals("https://84.198.58.199/mvc-showcase", actual.getRequestURL().toString());
+		assertEquals("https", actual.getScheme());
+		assertEquals("84.198.58.199", actual.getServerName());
+		assertEquals(443, actual.getServerPort());
+		assertTrue(actual.isSecure());
+
+		assertNull(actual.getHeader("X-Forwarded-Proto"));
+		assertNull(actual.getHeader("X-Forwarded-Host"));
+		assertNull(actual.getHeader("X-Forwarded-Port"));
+		assertEquals("bar", actual.getHeader("foo"));
+	}
+
+
+	private void testShouldFilter(String headerName) throws ServletException {
+		MockHttpServletRequest request = new MockHttpServletRequest();
+		request.addHeader(headerName, "1");
+		assertFalse(this.filter.shouldNotFilter(request));
+	}
+
+
+}