Updated documentation for Feign hierarchical clients

docs/src/main/asciidoc/spring-cloud-netflix.adoc

@@ -723,6 +723,42 @@ don't want to use Eureka, you can simply configure a list of servers
 in your external configuration (see
 <<spring-cloud-ribbon-without-eureka,above for example>>).
 
+[[spring-cloud-feign-inheritance]]
+=== Feign Inheritance Support
+
+Feign supports boilerplate apis via single-inheritance interfaces.
+This allows grouping common operations into convenient base interfaces.
+Together with Spring MVC you can share the same contract for your
+REST endpoint and Feign client.
+
+.UserService.java
+[source,java,indent=0]
+----
+public interface UserService {
+
+    @RequestMapping(method = RequestMethod.GET, value ="/users/{id}")
+    User getUser(@PathVariable("id") long id);
+}
+----
+
+.UserResource.java
+[source,java,indent=0]
+----
+@RestController
+public class UserResource implements UserService {
+
+}
+----
+
+.UserClient.java
+[source,java,indent=0]
+----
+@FeignClient("users")
+public interface UserClient extends UserService {
+
+}
+----
+
 == External Configuration: Archaius
 
 https://github.com/Netflix/archaius[Archaius] is the Netflix client side configuration library.  It is the library used by all of the Netflix OSS components for configuration.  Archaius is an extension of the http://commons.apache.org/proper/commons-configuration[Apache Commons Configuration] project.  It allows updates to configuration by either polling a source for changes or for a source to push changes to the client.  Archaius uses Dynamic<Type>Property classes as handles to properties.

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

@@ -49,6 +49,7 @@ import org.springframework.test.annotation.DirtiesContext;
 import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
 import org.springframework.test.context.web.WebAppConfiguration;
 import org.springframework.util.ReflectionUtils;
+import org.springframework.web.bind.annotation.PathVariable;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RequestMethod;
 import org.springframework.web.bind.annotation.RestController;
@@ -78,22 +79,34 @@ public class FeignHttpClientTests {
 	@Autowired
 	private Client feignClient;
 
-	// @FeignClient(value = "http://localhost:9876", loadbalance = false)
+	@Autowired
+	private UserClient userClient;
+
 	@FeignClient("localapp")
-	protected static interface TestClient {
+	protected interface TestClient extends BaseTestClient { }
+
+	protected interface BaseTestClient {
 		@RequestMapping(method = RequestMethod.GET, value = "/hello")
-		public Hello getHello();
+		Hello getHello();
 
 		@RequestMapping(method = RequestMethod.PATCH, value = "/hellop")
-		public ResponseEntity<Void> patchHello();
+		ResponseEntity<Void> patchHello();
+	}
+
+	protected interface UserService {
+		@RequestMapping(method = RequestMethod.GET, value ="/users/{id}")
+		User getUser(@PathVariable("id") long id);
 	}
 
+	@FeignClient("localapp")
+	protected interface UserClient extends UserService { }
+
 	@Configuration
 	@EnableAutoConfiguration
 	@RestController
 	@EnableFeignClients
 	@RibbonClient(name = "localapp", configuration = LocalRibbonClientConfiguration.class)
-	protected static class Application {
+	protected static class Application implements UserService {
 
 		@RequestMapping(method = RequestMethod.GET, value = "/hello")
 		public Hello getHello() {
@@ -105,6 +118,11 @@ public class FeignHttpClientTests {
 			return ResponseEntity.ok().header("X-Hello", "hello world patch").build();
 		}
 
+		@Override
+		public User getUser(@PathVariable("id") long id) {
+			return new User("John Smith");
+		}
+
 		public static void main(String[] args) {
 			new SpringApplicationBuilder(Application.class).properties(
 					"spring.application.name=feignclienttest",
@@ -137,6 +155,14 @@ public class FeignHttpClientTests {
 		assertThat(delegate, is(instanceOf(feign.httpclient.ApacheHttpClient.class)));
 	}
 
+	@Test
+	public void testFeignInheritanceSupport() {
+		assertNotNull("UserClient was null", userClient);
+		final User user = userClient.getUser(1);
+		assertNotNull("Returned user was null", user);
+		assertEquals("Users were different", user, new User("John Smith"));
+	}
+
 	@Data
 	@AllArgsConstructor
 	@NoArgsConstructor
@@ -144,6 +170,13 @@ public class FeignHttpClientTests {
 		private String message;
 	}
 
+	@Data
+	@AllArgsConstructor
+	@NoArgsConstructor
+	public static class User {
+		private String name;
+	}
+
 	// Load balancer with fixed server list for "local" pointing to localhost
 	@Configuration
 	static class LocalRibbonClientConfiguration {