Use case-insensitive ResponseEntity headers. Fixes gh-456. (#472)

spring-cloud-openfeign-core/src/main/java/org/springframework/cloud/openfeign/FeignAutoConfiguration.java

@@ -94,7 +94,8 @@ public class FeignAutoConfiguration {
 	@Bean
 	@ConditionalOnMissingBean(PageJacksonModule.class)
 	@ConditionalOnClass(name = "org.springframework.data.domain.Page")
-	@ConditionalOnProperty(value = "feign.autoconfiguration.jackson.enabled", havingValue = "true")
+	@ConditionalOnProperty(value = "feign.autoconfiguration.jackson.enabled",
+			havingValue = "true")
 	public Module pageJacksonModule() {
 		return new PageJacksonModule();
 	}
@@ -102,7 +103,8 @@ public class FeignAutoConfiguration {
 	@Bean
 	@ConditionalOnMissingBean(SortJacksonModule.class)
 	@ConditionalOnClass(name = "org.springframework.data.domain.Sort")
-	@ConditionalOnProperty(value = "feign.autoconfiguration.jackson.enabled", havingValue = "true")
+	@ConditionalOnProperty(value = "feign.autoconfiguration.jackson.enabled",
+			havingValue = "true")
 	public Module sortModule() {
 		return new SortJacksonModule();
 	}

spring-cloud-openfeign-core/src/main/java/org/springframework/cloud/openfeign/support/ResponseEntityDecoder.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2013-2020 the original author or authors.
+ * Copyright 2013-2021 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.
@@ -26,16 +26,16 @@ import feign.Response;
 import feign.codec.Decoder;
 
 import org.springframework.http.HttpEntity;
+import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseEntity;
-import org.springframework.util.LinkedMultiValueMap;
-import org.springframework.util.MultiValueMap;
 
 /**
  * Decoder adds compatibility for Spring MVC's ResponseEntity to any other decoder via
  * composition.
  *
  * @author chad jaros
+ * @author Olga Maciaszek-Sharma
  */
 public class ResponseEntityDecoder implements Decoder {
 
@@ -81,7 +81,7 @@ public class ResponseEntityDecoder implements Decoder {
 	@SuppressWarnings("unchecked")
 	private <T> ResponseEntity<T> createResponse(Object instance, Response response) {
 
-		MultiValueMap<String, String> headers = new LinkedMultiValueMap<>();
+		HttpHeaders headers = new HttpHeaders();
 		for (String key : response.headers().keySet()) {
 			headers.put(key, new LinkedList<>(response.headers().get(key)));
 		}

spring-cloud-openfeign-core/src/test/java/org/springframework/cloud/openfeign/SpringDecoderTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2013-2020 the original author or authors.
+ * Copyright 2013-2021 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.
@@ -32,7 +32,9 @@ import org.springframework.boot.test.context.SpringBootTest.WebEnvironment;
 import org.springframework.cloud.openfeign.test.NoSecurityConfiguration;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Import;
+import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpStatus;
+import org.springframework.http.MediaType;
 import org.springframework.http.ResponseEntity;
 import org.springframework.test.annotation.DirtiesContext;
 import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
@@ -45,6 +47,7 @@ import static org.assertj.core.api.Assertions.assertThat;
 
 /**
  * @author Spencer Gibb
+ * @author Olga Maciaszek-Sharma
  */
 @RunWith(SpringJUnit4ClassRunner.class)
 @SpringBootTest(classes = SpringDecoderTests.Application.class,
@@ -152,6 +155,14 @@ public class SpringDecoderTests extends FeignClientFactoryBean {
 		assertThat(response.getBody()).as("response body was not null").isNull();
 	}
 
+	@Test
+	// Issue: https://github.com/spring-cloud/spring-cloud-openfeign/issues/456
+	public void testResponseEntityHeaders() {
+		ResponseEntity<String> response = testClient().getContentType();
+		assertThat(response.getHeaders().getContentType())
+				.isEqualTo(MediaType.APPLICATION_JSON);
+	}
+
 	protected interface TestClient {
 
 		@RequestMapping(method = RequestMethod.GET, value = "/helloresponse")
@@ -175,6 +186,9 @@ public class SpringDecoderTests extends FeignClientFactoryBean {
 		@GetMapping("/helloWildcard")
 		ResponseEntity<?> getWildcard();
 
+		@GetMapping(path = "/contentType", produces = MediaType.APPLICATION_JSON_VALUE)
+		ResponseEntity<String> getContentType();
+
 	}
 
 	public static class Hello {
@@ -262,6 +276,13 @@ public class SpringDecoderTests extends FeignClientFactoryBean {
 			return ResponseEntity.ok(new Hello("wildcard"));
 		}
 
+		@Override
+		public ResponseEntity<String> getContentType() {
+			return ResponseEntity.ok()
+					.header(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON_VALUE)
+					.body("test");
+		}
+
 	}
 
 }