Run http headers filters for response after status code is set.

This makes the status code available to the filters.

fixes gh-757

spring-cloud-gateway-core/src/main/java/org/springframework/cloud/gateway/filter/NettyRoutingFilter.java

@@ -137,10 +137,6 @@ public class NettyRoutingFilter implements GlobalFilter, Ordered {
 				exchange.getAttributes().put(ORIGINAL_RESPONSE_CONTENT_TYPE_ATTR, contentTypeValue);
 			}
 
-			HttpHeaders filteredResponseHeaders = HttpHeadersFilter.filter(
-					this.headersFilters.getIfAvailable(), headers, exchange, Type.RESPONSE);
-			
-			response.getHeaders().putAll(filteredResponseHeaders);
 			HttpStatus status = HttpStatus.resolve(res.status().code());
 			if (status != null) {
 				response.setStatusCode(status);
@@ -151,6 +147,12 @@ public class NettyRoutingFilter implements GlobalFilter, Ordered {
 				throw new IllegalStateException("Unable to set status code on response: " +res.status().code()+", "+response.getClass());
 			}
 
+			// make sure headers filters run after setting status so it is available in response
+			HttpHeaders filteredResponseHeaders = HttpHeadersFilter.filter(
+					this.headersFilters.getIfAvailable(), headers, exchange, Type.RESPONSE);
+
+			response.getHeaders().putAll(filteredResponseHeaders);
+
 			// Defer committing the response until all route filters have run
 			// Put client response as ServerWebExchange attribute and write response later NettyWriteResponseFilter
 			exchange.getAttributes().put(CLIENT_RESPONSE_ATTR, res);

spring-cloud-gateway-core/src/test/java/org/springframework/cloud/gateway/filter/headers/HttpStatusInResponseHeadersFilterTests.java

@@ -0,0 +1,77 @@
+/*
+ * Copyright 2013-2019 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.cloud.gateway.filter.headers;
+
+import org.junit.Test;
+
+import org.junit.runner.RunWith;
+import org.springframework.boot.SpringBootConfiguration;
+import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.cloud.gateway.test.BaseWebClientTests;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Import;
+import org.springframework.http.HttpHeaders;
+import org.springframework.http.HttpStatus;
+import org.springframework.test.annotation.DirtiesContext;
+import org.springframework.test.context.junit4.SpringRunner;
+import org.springframework.web.server.ServerWebExchange;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.springframework.boot.test.context.SpringBootTest.WebEnvironment.RANDOM_PORT;
+
+/**
+ * @author Spencer Gibb
+ */
+@RunWith(SpringRunner.class)
+@SpringBootTest(webEnvironment = RANDOM_PORT)
+@DirtiesContext
+public class HttpStatusInResponseHeadersFilterTests extends BaseWebClientTests  {
+
+	@Test
+	public void statusCodeAvailableInResponseHttpHeadersFilter() {
+		testClient.get()
+				.uri("/get")
+				.exchange()
+				.expectStatus().isOk();
+	}
+
+	@EnableAutoConfiguration
+	@SpringBootConfiguration
+	@Import(DefaultTestConfig.class)
+	public static class TestConfig {
+
+		@Bean
+		public HttpHeadersFilter checkStatusFilter() {
+			return new HttpHeadersFilter() {
+				@Override
+				public HttpHeaders filter(HttpHeaders input, ServerWebExchange exchange) {
+					HttpStatus statusCode = exchange.getResponse().getStatusCode();
+					assertThat(statusCode).isEqualTo(HttpStatus.OK);
+					return input;
+				}
+
+				@Override
+				public boolean supports(Type type) {
+					return type == Type.RESPONSE;
+				}
+			};
+		}
+
+	}
+}