Ensure that detected request factories are initialized

Closes gh-9797

spring-boot/src/main/java/org/springframework/boot/web/client/RestTemplateBuilder.java

@@ -29,6 +29,7 @@ import java.util.Map;
 import java.util.Set;
 
 import org.springframework.beans.BeanUtils;
+import org.springframework.beans.factory.InitializingBean;
 import org.springframework.http.client.AbstractClientHttpRequestFactoryWrapper;
 import org.springframework.http.client.ClientHttpRequestFactory;
 import org.springframework.http.client.ClientHttpRequestInterceptor;
@@ -591,12 +592,27 @@ public class RestTemplateBuilder {
 			if (ClassUtils.isPresent(candidate.getKey(), classLoader)) {
 				Class<?> factoryClass = ClassUtils.resolveClassName(candidate.getValue(),
 						classLoader);
-				return (ClientHttpRequestFactory) BeanUtils.instantiate(factoryClass);
+				ClientHttpRequestFactory requestFactory = (ClientHttpRequestFactory) BeanUtils
+						.instantiate(factoryClass);
+				initializeIfNecessary(requestFactory);
+				return requestFactory;
 			}
 		}
 		return new SimpleClientHttpRequestFactory();
 	}
 
+	private void initializeIfNecessary(ClientHttpRequestFactory requestFactory) {
+		if (requestFactory instanceof InitializingBean) {
+			try {
+				((InitializingBean) requestFactory).afterPropertiesSet();
+			}
+			catch (Exception ex) {
+				throw new IllegalStateException(
+						"Failed to initialize request factory " + requestFactory, ex);
+			}
+		}
+	}
+
 	private <T> Set<T> append(Set<T> set, T addition) {
 		Set<T> result = new LinkedHashSet<T>(
 				set == null ? Collections.<T>emptySet() : set);

spring-boot/src/test/java/org/springframework/boot/web/client/RestTemplateBuilderNettyTests.java

@@ -0,0 +1,49 @@
+/*
+ * Copyright 2012-2017 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
+ *
+ *      http://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.boot.web.client;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import org.springframework.boot.junit.runner.classpath.ClassPathExclusions;
+import org.springframework.boot.junit.runner.classpath.ModifiedClassPathRunner;
+import org.springframework.http.client.ClientHttpRequestFactory;
+import org.springframework.http.client.Netty4ClientHttpRequestFactory;
+import org.springframework.test.util.ReflectionTestUtils;
+import org.springframework.web.client.RestTemplate;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link RestTemplateBuilder} when Netty is used by default.
+ *
+ * @author Andy Wilkinson
+ */
+@RunWith(ModifiedClassPathRunner.class)
+@ClassPathExclusions({ "httpclient-*.jar", "okhttp-*.jar" })
+public class RestTemplateBuilderNettyTests {
+
+	@Test
+	public void sslContextIsInitialized() {
+		RestTemplate restTemplate = new RestTemplateBuilder().build();
+		ClientHttpRequestFactory requestFactory = restTemplate.getRequestFactory();
+		assertThat(requestFactory).isInstanceOf(Netty4ClientHttpRequestFactory.class);
+		assertThat(ReflectionTestUtils.getField(requestFactory, "sslContext"))
+				.isNotNull();
+	}
+
+}