fallback support FacotryBean (#823)

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

@@ -19,9 +19,13 @@ package org.springframework.cloud.openfeign;
 import feign.Feign;
 import feign.Target;
 
+import org.springframework.beans.factory.FactoryBean;
 import org.springframework.cloud.client.circuitbreaker.CircuitBreakerFactory;
 import org.springframework.util.StringUtils;
 
+/**
+ * @author 黄学敏（huangxuemin)
+ */
 @SuppressWarnings("unchecked")
 class FeignCircuitBreakerTargeter implements Targeter {
 
@@ -78,10 +82,27 @@ class FeignCircuitBreakerTargeter implements Targeter {
 							beanType, feignClientName));
 		}
 
-		if (!targetType.isAssignableFrom(beanType)) {
-			throw new IllegalStateException(String.format("Incompatible " + fallbackMechanism
-					+ " instance. Fallback/fallbackFactory of type %s is not assignable to %s for feign client %s",
-					beanType, targetType, feignClientName));
+		if (fallbackInstance instanceof FactoryBean<?> factoryBean) {
+			try {
+				fallbackInstance = factoryBean.getObject();
+			}
+			catch (Exception e) {
+				throw new IllegalStateException(fallbackMechanism + " create fail", e);
+			}
+
+			if (!targetType.isAssignableFrom(fallbackInstance.getClass())) {
+				throw new IllegalStateException(String.format("Incompatible " + fallbackMechanism
+						+ " instance. Fallback/fallbackFactory of type %s is not assignable to %s for feign client %s",
+						fallbackInstance.getClass(), targetType, feignClientName));
+			}
+
+		}
+		else {
+			if (!targetType.isAssignableFrom(beanType)) {
+				throw new IllegalStateException(String.format("Incompatible " + fallbackMechanism
+						+ " instance. Fallback/fallbackFactory of type %s is not assignable to %s for feign client %s",
+						beanType, targetType, feignClientName));
+			}
 		}
 		return (T) fallbackInstance;
 	}

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

@@ -0,0 +1,134 @@
+/*
+ * Copyright 2013-2023 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
+ *
+ *      https://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.openfeign.circuitbreaker;
+
+import java.util.function.Function;
+import java.util.function.Supplier;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.beans.factory.FactoryBean;
+import org.springframework.boot.autoconfigure.AutoConfigurations;
+import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.boot.test.context.runner.ApplicationContextRunner;
+import org.springframework.cloud.client.circuitbreaker.CircuitBreaker;
+import org.springframework.cloud.client.circuitbreaker.CircuitBreakerFactory;
+import org.springframework.cloud.client.circuitbreaker.ConfigBuilder;
+import org.springframework.cloud.openfeign.EnableFeignClients;
+import org.springframework.cloud.openfeign.FeignAutoConfiguration;
+import org.springframework.cloud.openfeign.FeignClient;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.web.bind.annotation.GetMapping;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * @author 黄学敏（huangxuemin)
+ */
+class FallbackSupportFactoryBeanTests {
+
+	private static final String FACTORY_BEAN_FALLBACK_MESSAGE = "factoryBean fallback message";
+
+	private static final String ORIGINAL_FALLBACK_MESSAGE = "OriginalFeign fallback message";
+
+	private final ApplicationContextRunner runner = new ApplicationContextRunner()
+			.withBean(FactoryBeanFallbackFeignFallback.class).withBean(OriginalFeignFallback.class)
+			.withConfiguration(AutoConfigurations.of(TestConfiguration.class, FeignAutoConfiguration.class))
+			.withBean(CircuitBreakerFactory.class, () -> new CircuitBreakerFactory() {
+				@Override
+				public CircuitBreaker create(String id) {
+					return new CircuitBreaker() {
+						@Override
+						public <T> T run(Supplier<T> toRun, Function<Throwable, T> fallback) {
+							try {
+								return toRun.get();
+							}
+							catch (Throwable t) {
+								return fallback.apply(t);
+							}
+						}
+					};
+				}
+
+				@Override
+				protected ConfigBuilder configBuilder(String id) {
+					return null;
+				}
+
+				@Override
+				public void configureDefault(Function defaultConfiguration) {
+
+				}
+			}).withPropertyValues("spring.cloud.openfeign.circuitbreaker.enabled=true");
+
+	@Test
+	void shouldRunFallbackFromBeanOrFactoryBean() {
+		runner.run(ctx -> {
+			assertThat(ctx.getBean(OriginalFeign.class).get().equals(ORIGINAL_FALLBACK_MESSAGE)).isTrue();
+			assertThat(ctx.getBean(FactoryBeanFallbackFeign.class).get().equals(FACTORY_BEAN_FALLBACK_MESSAGE))
+					.isTrue();
+		});
+	}
+
+	@Configuration(proxyBeanMethods = false)
+	@EnableFeignClients(clients = { FallbackSupportFactoryBeanTests.OriginalFeign.class,
+			FallbackSupportFactoryBeanTests.FactoryBeanFallbackFeign.class })
+	@EnableAutoConfiguration
+	private static class TestConfiguration {
+
+	}
+
+	@FeignClient(name = "original", url = "https://original", fallback = OriginalFeignFallback.class)
+	interface OriginalFeign {
+
+		@GetMapping("/")
+		String get();
+
+	}
+
+	@FeignClient(name = "factoryBean", url = "https://factoryBean", fallback = FactoryBeanFallbackFeignFallback.class)
+	interface FactoryBeanFallbackFeign {
+
+		@GetMapping("/")
+		String get();
+
+	}
+
+	private static class FactoryBeanFallbackFeignFallback implements FactoryBean<FactoryBeanFallbackFeign> {
+
+		@Override
+		public FactoryBeanFallbackFeign getObject() {
+			return () -> FACTORY_BEAN_FALLBACK_MESSAGE;
+		}
+
+		@Override
+		public Class<?> getObjectType() {
+			return FactoryBeanFallbackFeign.class;
+		}
+
+	}
+
+	private static class OriginalFeignFallback implements OriginalFeign {
+
+		@Override
+		public String get() {
+			return ORIGINAL_FALLBACK_MESSAGE;
+		}
+
+	}
+
+}