Add check to prevent StackOverflowError (#2580)

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

@@ -17,7 +17,6 @@
 package org.springframework.cloud.netflix.feign;
 
 import java.io.IOException;
-import java.lang.annotation.Annotation;
 import java.net.MalformedURLException;
 import java.net.URI;
 import java.net.URISyntaxException;
@@ -36,7 +35,6 @@ import org.springframework.beans.factory.support.AbstractBeanDefinition;
 import org.springframework.beans.factory.support.BeanDefinitionBuilder;
 import org.springframework.beans.factory.support.BeanDefinitionReaderUtils;
 import org.springframework.beans.factory.support.BeanDefinitionRegistry;
-import org.springframework.context.ConfigurableApplicationContext;
 import org.springframework.context.EnvironmentAware;
 import org.springframework.context.ResourceLoaderAware;
 import org.springframework.context.annotation.ClassPathScanningCandidateComponentProvider;
@@ -208,6 +206,14 @@ class FeignClientsRegistrar implements ImportBeanDefinitionRegistrar,
 		AnnotationAttributes annotation = AnnotationAttributes.fromMap(attributes);
 		// This blows up if an aliased property is overspecified
 		// FIXME annotation.getAliasedString("name", FeignClient.class, null);
+		Assert.isTrue(
+			!annotation.getClass("fallback").isInterface(),
+			"Fallback class must implement the interface annotated by @FeignClient"
+		);
+		Assert.isTrue(
+			!annotation.getClass("fallbackFactory").isInterface(),
+			"Fallback factory must produce instances of fallback classes that implement the interface annotated by @FeignClient"
+		);
 	}
 
 	/* for testing */ String getName(Map<String, Object> attributes) {

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

@@ -20,13 +20,19 @@ package org.springframework.cloud.netflix.feign;
 import java.util.Collections;
 
 import org.junit.Test;
+import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+import org.springframework.context.annotation.Configuration;
 import org.springframework.mock.env.MockEnvironment;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RequestMethod;
 
 import static org.hamcrest.Matchers.is;
 import static org.junit.Assert.assertThat;
 
 /**
  * @author Spencer Gibb
+ * @author Gang Li
  */
 public class FeignClientsRegistrarTests {
 
@@ -74,4 +80,42 @@ public class FeignClientsRegistrarTests {
 		registrar.setEnvironment(new MockEnvironment());
 		return registrar.getName(Collections.<String, Object>singletonMap("name", name));
 	}
+
+
+	@Test(expected = IllegalArgumentException.class)
+	public void testFallback() {
+		new AnnotationConfigApplicationContext(FallbackTestConfig.class);
+	}
+
+	@Test(expected = IllegalArgumentException.class)
+	public void testFallbackFactory() {
+		new AnnotationConfigApplicationContext(FallbackFactoryTestConfig.class);
+	}
+
+	@Configuration
+	@EnableAutoConfiguration
+	@EnableFeignClients(clients = { FeignClientsRegistrarTests.FallbackClient.class})
+	protected static class FallbackTestConfig {
+
+	}
+
+	@FeignClient(name = "fallbackTestClient", url = "http://localhost:8080/", fallback = FallbackClient.class)
+	protected interface FallbackClient {
+		@RequestMapping(method = RequestMethod.GET, value = "/hello")
+		String fallbackTest();
+	}
+
+	@Configuration
+	@EnableAutoConfiguration
+	@EnableFeignClients(clients = { FeignClientsRegistrarTests.FallbackFactoryClient.class})
+	protected static class FallbackFactoryTestConfig {
+
+	}
+
+	@FeignClient(name = "fallbackFactoryTestClient", url = "http://localhost:8081/", fallbackFactory = FallbackFactoryClient.class)
+	protected interface FallbackFactoryClient {
+		@RequestMapping(method = RequestMethod.GET, value = "/hello")
+		String fallbackFactoryTest();
+	}
+
 }