Add support for Wildcard Types in Feign Client. Fixes gh-1676

spring-cloud-netflix-core/src/main/java/org/springframework/cloud/netflix/feign/support/SpringDecoder.java

@@ -16,13 +16,10 @@
 
 package org.springframework.cloud.netflix.feign.support;
 
-import static org.springframework.cloud.netflix.feign.support.FeignUtils.getHttpHeaders;
-
-import java.io.IOException;
-import java.io.InputStream;
-import java.lang.reflect.ParameterizedType;
-import java.lang.reflect.Type;
-
+import feign.FeignException;
+import feign.Response;
+import feign.codec.DecodeException;
+import feign.codec.Decoder;
 import org.springframework.beans.factory.ObjectFactory;
 import org.springframework.boot.autoconfigure.web.HttpMessageConverters;
 import org.springframework.http.HttpHeaders;
@@ -30,10 +27,13 @@ import org.springframework.http.HttpStatus;
 import org.springframework.http.client.ClientHttpResponse;
 import org.springframework.web.client.HttpMessageConverterExtractor;
 
-import feign.FeignException;
-import feign.Response;
-import feign.codec.DecodeException;
-import feign.codec.Decoder;
+import java.io.IOException;
+import java.io.InputStream;
+import java.lang.reflect.ParameterizedType;
+import java.lang.reflect.Type;
+import java.lang.reflect.WildcardType;
+
+import static org.springframework.cloud.netflix.feign.support.FeignUtils.getHttpHeaders;
 
 /**
  * @author Spencer Gibb
@@ -49,7 +49,7 @@ public class SpringDecoder implements Decoder {
 	@Override
 	public Object decode(final Response response, Type type) throws IOException,
 			FeignException {
-		if (type instanceof Class || type instanceof ParameterizedType) {
+		if (type instanceof Class || type instanceof ParameterizedType || type instanceof WildcardType) {
 			@SuppressWarnings({ "unchecked", "rawtypes" })
 			HttpMessageConverterExtractor<?> extractor = new HttpMessageConverterExtractor(
 					type, this.messageConverters.getObject().getConverters());

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

@@ -16,13 +16,9 @@
 
 package org.springframework.cloud.netflix.feign;
 
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertNotNull;
-import static org.junit.Assert.assertNull;
-
-import java.util.ArrayList;
-import java.util.List;
-
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.springframework.beans.factory.annotation.Autowired;
@@ -36,13 +32,16 @@ import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseEntity;
 import org.springframework.test.annotation.DirtiesContext;
 import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
+import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RequestMethod;
 import org.springframework.web.bind.annotation.RestController;
 
-import lombok.AllArgsConstructor;
-import lombok.Data;
-import lombok.NoArgsConstructor;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+
+import static org.junit.Assert.*;
 
 /**
  * @author Spencer Gibb
@@ -109,6 +108,19 @@ public class SpringDecoderTests extends FeignClientFactoryBean {
 	}
 
 	@Test
+	@SuppressWarnings("unchecked")
+	public void testWildcardTypeDecode() {
+		ResponseEntity<?> wildcard = testClient().getWildcard();
+		assertNotNull("wildcard was null", wildcard);
+		assertEquals("wrong status code", HttpStatus.OK, wildcard.getStatusCode());
+		Object wildcardBody = wildcard.getBody();
+		assertNotNull("wildcardBody was null", wildcardBody);
+		assertTrue("wildcard not an instance of Map", wildcardBody instanceof Map);
+		Map<String, String> hello = (Map<String, String>) wildcardBody;
+		assertEquals("first hello didn't match", "wildcard", hello.get("message"));
+	}
+
+	@Test
 	public void testResponseEntityVoid() {
 		ResponseEntity<Void> response = testClient().getHelloVoid();
 		assertNotNull("response was null", response);
@@ -156,6 +168,9 @@ public class SpringDecoderTests extends FeignClientFactoryBean {
 
 		@RequestMapping(method = RequestMethod.GET, value = "/hellonotfound")
 		ResponseEntity<String> getNotFound();
+
+		@GetMapping("/helloWildcard")
+		ResponseEntity<?> getWildcard();
 	}
 
 	@Configuration
@@ -199,6 +214,11 @@ public class SpringDecoderTests extends FeignClientFactoryBean {
 			return ResponseEntity.status(HttpStatus.NOT_FOUND).body((String) null);
 		}
 
+		@Override
+		public ResponseEntity<?> getWildcard() {
+			return ResponseEntity.ok(new Hello("wildcard"));
+		}
+
 		public static void main(String[] args) {
 			new SpringApplicationBuilder(Application.class)
 					.properties("spring.application.name=springdecodertest",