Handles null response with Feign; fixes gh-1823

spring-cloud-sleuth-autoconfigure/src/test/java/org/springframework/cloud/sleuth/autoconfig/brave/instrument/web/BraveHttpConfigurationTests.java

@@ -143,7 +143,7 @@ public class BraveHttpConfigurationTests {
 	}
 
 	/**
-	 * Shows bean aliases work to configure the same instance for both client and server
+	 * Shows bean aliases work to configure the same instance for both client and server.
 	 */
 	@Test
 	public void configuresUserProvidedHttpClientAndServerParser() {

spring-cloud-sleuth-autoconfigure/src/test/java/org/springframework/cloud/sleuth/autoconfig/instrument/web/SkipPatternProviderConfigTest.java

@@ -292,7 +292,7 @@ public class SkipPatternProviderConfigTest {
 	}
 
 	/**
-	 * Extracts the patterns from pattern provider
+	 * Extracts the patterns from pattern provider.
 	 */
 	private String extractPattern(ApplicationContext context) {
 		SkipPatternProvider skipPatternProvider = context.getBean(SkipPatternProvider.class);
@@ -300,7 +300,7 @@ public class SkipPatternProviderConfigTest {
 	}
 
 	/**
-	 * Extracts all single patterns
+	 * Extracts all single patterns.
 	 */
 	private Collection<String> extractAllPatterns(ApplicationContext context) {
 		return context.getBeansOfType(SingleSkipPattern.class).values().stream().map(SingleSkipPattern::skipPattern)

spring-cloud-sleuth-brave/src/main/java/org/springframework/cloud/sleuth/brave/bridge/BraveHttpClientHandler.java

@@ -16,6 +16,9 @@
 
 package org.springframework.cloud.sleuth.brave.bridge;
 
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+
 import org.springframework.cloud.sleuth.Span;
 import org.springframework.cloud.sleuth.TraceContext;
 import org.springframework.cloud.sleuth.http.HttpClientHandler;
@@ -30,6 +33,8 @@ import org.springframework.cloud.sleuth.http.HttpClientResponse;
  */
 public class BraveHttpClientHandler implements HttpClientHandler {
 
+	private static final Log log = LogFactory.getLog(BraveHttpClientHandler.class);
+
 	final brave.http.HttpClientHandler<brave.http.HttpClientRequest, brave.http.HttpClientResponse> delegate;
 
 	public BraveHttpClientHandler(
@@ -54,6 +59,12 @@ public class BraveHttpClientHandler implements HttpClientHandler {
 
 	@Override
 	public void handleReceive(HttpClientResponse response, Span span) {
+		if (response == null) {
+			if (log.isDebugEnabled()) {
+				log.debug("Response is null, will not handle receiving of span [" + span + "]");
+			}
+			return;
+		}
 		this.delegate.handleReceive(BraveHttpClientResponse.toBrave(response), BraveSpan.toBrave(span));
 	}
 

spring-cloud-sleuth-brave/src/test/java/org/springframework/cloud/sleuth/brave/bridge/BraveHttpClientHandlerTests.java

@@ -0,0 +1,36 @@
+/*
+ * Copyright 2013-2020 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.sleuth.brave.bridge;
+
+import brave.Tracing;
+import brave.http.HttpClientHandler;
+import brave.http.HttpTracing;
+import org.junit.jupiter.api.Test;
+
+class BraveHttpClientHandlerTests {
+
+	@Test
+	void should_not_throw_exception_when_response_null() {
+		Tracing tracing = Tracing.newBuilder().build();
+		brave.http.HttpClientHandler<brave.http.HttpClientRequest, brave.http.HttpClientResponse> delegate = HttpClientHandler
+				.create(HttpTracing.newBuilder(tracing).build());
+		BraveHttpClientHandler handler = new BraveHttpClientHandler(delegate);
+
+		handler.handleReceive(null, new BraveSpan(tracing.currentTracer().nextSpan()));
+	}
+
+}