add customizer for feign builder (#289)

* add customizer for feign builder

* support @Order for customizers

* switch to annotation aware comparator for @Order support

* remove intermediate instances

* removed default feign builder customizer

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

@@ -0,0 +1,31 @@
+/*
+ * Copyright 2013-2019 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;
+
+import feign.Feign;
+
+/**
+ * Allows application to customize the Feign builder.
+ *
+ * @author Matt King
+ */
+@FunctionalInterface
+public interface FeignBuilderCustomizer {
+
+	void customize(Feign.Builder builder);
+
+}

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

@@ -41,6 +41,7 @@ import org.springframework.beans.factory.NoSuchBeanDefinitionException;
 import org.springframework.cloud.openfeign.loadbalancer.FeignBlockingLoadBalancerClient;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.ApplicationContextAware;
+import org.springframework.core.annotation.AnnotationAwareOrderComparator;
 import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
 
@@ -49,6 +50,7 @@ import org.springframework.util.StringUtils;
  * @author Venil Noronha
  * @author Eko Kurniawan Khannedy
  * @author Gregor Zurowski
+ * @author Matt King
  */
 class FeignClientFactoryBean
 		implements FactoryBean<Object>, InitializingBean, ApplicationContextAware {
@@ -96,10 +98,23 @@ class FeignClientFactoryBean
 		// @formatter:on
 
 		configureFeign(context, builder);
+		applyBuildCustomizers(context, builder);
 
 		return builder;
 	}
 
+	private void applyBuildCustomizers(FeignContext context, Feign.Builder builder) {
+		Map<String, FeignBuilderCustomizer> customizerMap = context
+				.getInstances(contextId, FeignBuilderCustomizer.class);
+
+		if (customizerMap != null) {
+			customizerMap.values().stream()
+					.sorted(AnnotationAwareOrderComparator.INSTANCE)
+					.forEach(feignBuilderCustomizer -> feignBuilderCustomizer
+							.customize(builder));
+		}
+	}
+
 	protected void configureFeign(FeignContext context, Feign.Builder builder) {
 		FeignClientProperties properties = this.applicationContext
 				.getBean(FeignClientProperties.class);

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

@@ -0,0 +1,160 @@
+/*
+ * Copyright 2013-2019 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;
+
+import java.lang.reflect.Field;
+
+import feign.Feign;
+import feign.Logger;
+import org.junit.Test;
+
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Import;
+import org.springframework.core.annotation.Order;
+import org.springframework.util.ReflectionUtils;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * @author Matt King
+ */
+public class FeignBuilderCustomizerTests {
+
+	@Test
+	public void testBuilderCustomizer() {
+		AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(
+				FeignBuilderCustomizerTests.SampleConfiguration2.class);
+
+		FeignClientFactoryBean clientFactoryBean = context
+				.getBean(FeignClientFactoryBean.class);
+		FeignContext feignContext = context.getBean(FeignContext.class);
+
+		Feign.Builder builder = clientFactoryBean.feign(feignContext);
+		assertFeignBuilderField(builder, "logLevel", Logger.Level.HEADERS);
+		assertFeignBuilderField(builder, "decode404", true);
+
+		context.close();
+	}
+
+	private void assertFeignBuilderField(Feign.Builder builder, String fieldName,
+			Object expectedValue) {
+		Field builderField = ReflectionUtils.findField(Feign.Builder.class, fieldName);
+		ReflectionUtils.makeAccessible(builderField);
+
+		Object value = ReflectionUtils.getField(builderField, builder);
+		assertThat(value).as("Expected value for the field '" + fieldName + "':")
+				.isEqualTo(expectedValue);
+	}
+
+	@Test
+	public void testBuildCustomizerOrdered() {
+		AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(
+				FeignBuilderCustomizerTests.SampleConfiguration3.class);
+
+		FeignClientFactoryBean clientFactoryBean = context
+				.getBean(FeignClientFactoryBean.class);
+		FeignContext feignContext = context.getBean(FeignContext.class);
+
+		Feign.Builder builder = clientFactoryBean.feign(feignContext);
+		assertFeignBuilderField(builder, "logLevel", Logger.Level.FULL);
+		assertFeignBuilderField(builder, "decode404", true);
+
+		context.close();
+	}
+
+	private static FeignClientFactoryBean defaultFeignClientFactoryBean() {
+		FeignClientFactoryBean feignClientFactoryBean = new FeignClientFactoryBean();
+		feignClientFactoryBean.setContextId("test");
+		feignClientFactoryBean.setName("test");
+		feignClientFactoryBean.setType(FeignClientFactoryTests.TestType.class);
+		feignClientFactoryBean.setPath("");
+		feignClientFactoryBean.setUrl("http://some.absolute.url");
+		return feignClientFactoryBean;
+	}
+
+	@Configuration(proxyBeanMethods = false)
+	@Import(FeignClientsConfiguration.class)
+	protected static class SampleConfiguration2 {
+
+		@Bean
+		FeignContext feignContext() {
+			return new FeignContext();
+		}
+
+		@Bean
+		FeignClientProperties feignClientProperties() {
+			return new FeignClientProperties();
+		}
+
+		@Bean
+		FeignBuilderCustomizer feignBuilderCustomizer() {
+			return builder -> builder.logLevel(Logger.Level.HEADERS);
+		}
+
+		@Bean
+		FeignBuilderCustomizer feignBuilderCustomizer2() {
+			return Feign.Builder::decode404;
+		}
+
+		@Bean
+		FeignClientFactoryBean feignClientFactoryBean() {
+			return defaultFeignClientFactoryBean();
+		}
+
+	}
+
+	@Configuration(proxyBeanMethods = false)
+	@Import(FeignClientsConfiguration.class)
+	protected static class SampleConfiguration3 {
+
+		@Bean
+		FeignContext feignContext() {
+			return new FeignContext();
+		}
+
+		@Bean
+		FeignClientProperties feignClientProperties() {
+			return new FeignClientProperties();
+		}
+
+		@Bean
+		@Order(1)
+		FeignBuilderCustomizer feignBuilderCustomizer() {
+			return builder -> builder.logLevel(Logger.Level.HEADERS);
+		}
+
+		@Bean
+		@Order(2)
+		FeignBuilderCustomizer feignBuilderCustomizer1() {
+			return builder -> builder.logLevel(Logger.Level.FULL);
+		}
+
+		@Bean
+		FeignBuilderCustomizer feignBuilderCustomizer2() {
+			return Feign.Builder::decode404;
+		}
+
+		@Bean
+		FeignClientFactoryBean feignClientFactoryBean() {
+			return defaultFeignClientFactoryBean();
+		}
+
+	}
+
+}