TestRestTemplate should not override request factory

Previously `TestRestTemplate` would override the configured
`ClientHttpRequestFactory` if the Apache HTTP client library was on
classpath.

This commit fixes two issues:

1. The existing `ClientHttpRequestFactory` is overridden *only* if it is
using the Apache HTTP client variant, in order to wrap it with the
`TestRestTemplate` custom support

2. Calling `withBasicAuth` will no longer directly use the request
factory returned by the internal `RestTemplate`; if client interceptors
are configured, the request factory is wrapped with an
`InterceptingClientHttpRequestFactory`. If we don't unwrap it,
interceptors are copied/applied twice in the newly created
`TestRestTemplate` instance. For that, we need to use reflection as the
underlying request factory is not accessible directly.

Closes gh-8697

spring-boot-project/spring-boot-test/src/main/java/org/springframework/boot/test/web/client/TestRestTemplate.java

@@ -17,6 +17,7 @@
 package org.springframework.boot.test.web.client;
 
 import java.io.IOException;
+import java.lang.reflect.Field;
 import java.net.URI;
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -45,12 +46,14 @@ import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpMethod;
 import org.springframework.http.RequestEntity;
 import org.springframework.http.ResponseEntity;
+import org.springframework.http.client.ClientHttpRequestFactory;
 import org.springframework.http.client.ClientHttpRequestInterceptor;
 import org.springframework.http.client.ClientHttpResponse;
 import org.springframework.http.client.HttpComponentsClientHttpRequestFactory;
+import org.springframework.http.client.InterceptingClientHttpRequestFactory;
 import org.springframework.http.client.support.BasicAuthorizationInterceptor;
 import org.springframework.util.Assert;
-import org.springframework.util.ClassUtils;
+import org.springframework.util.ReflectionUtils;
 import org.springframework.web.client.DefaultResponseErrorHandler;
 import org.springframework.web.client.RequestCallback;
 import org.springframework.web.client.ResponseExtractor;
@@ -135,7 +138,8 @@ public class TestRestTemplate {
 			HttpClientOption... httpClientOptions) {
 		Assert.notNull(restTemplate, "RestTemplate must not be null");
 		this.httpClientOptions = httpClientOptions;
-		if (ClassUtils.isPresent("org.apache.http.client.config.RequestConfig", null)) {
+		if (restTemplate.getRequestFactory().getClass().getName()
+				.equals("org.springframework.http.client.HttpComponentsClientHttpRequestFactory")) {
 			restTemplate.setRequestFactory(
 					new CustomHttpComponentsClientHttpRequestFactory(httpClientOptions));
 		}
@@ -1021,7 +1025,7 @@ public class TestRestTemplate {
 		RestTemplate restTemplate = new RestTemplate();
 		restTemplate.setMessageConverters(getRestTemplate().getMessageConverters());
 		restTemplate.setInterceptors(getRestTemplate().getInterceptors());
-		restTemplate.setRequestFactory(getRestTemplate().getRequestFactory());
+		restTemplate.setRequestFactory(getRequestFactory(getRestTemplate()));
 		restTemplate.setUriTemplateHandler(getRestTemplate().getUriTemplateHandler());
 		TestRestTemplate testRestTemplate = new TestRestTemplate(restTemplate, username,
 				password, this.httpClientOptions);
@@ -1030,6 +1034,18 @@ public class TestRestTemplate {
 		return testRestTemplate;
 	}
 
+	private ClientHttpRequestFactory getRequestFactory(RestTemplate restTemplate) {
+		ClientHttpRequestFactory requestFactory = restTemplate.getRequestFactory();
+		if (InterceptingClientHttpRequestFactory.class.isAssignableFrom(requestFactory.getClass())) {
+			Field requestFactoryField = ReflectionUtils
+					.findField(RestTemplate.class, "requestFactory");
+			ReflectionUtils.makeAccessible(requestFactoryField);
+			requestFactory = (ClientHttpRequestFactory)
+					ReflectionUtils.getField(requestFactoryField, getRestTemplate());
+		}
+		return requestFactory;
+	}
+
 	@SuppressWarnings({ "rawtypes", "unchecked" })
 	private RequestEntity<?> createRequestEntityWithRootAppliedUri(
 			RequestEntity<?> requestEntity) {

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

@@ -37,6 +37,8 @@ import org.springframework.http.client.ClientHttpRequestFactory;
 import org.springframework.http.client.ClientHttpRequestInterceptor;
 import org.springframework.http.client.HttpComponentsClientHttpRequestFactory;
 import org.springframework.http.client.InterceptingClientHttpRequestFactory;
+import org.springframework.http.client.OkHttp3ClientHttpRequestFactory;
+import org.springframework.http.client.SimpleClientHttpRequestFactory;
 import org.springframework.http.client.support.BasicAuthorizationInterceptor;
 import org.springframework.mock.env.MockEnvironment;
 import org.springframework.mock.http.client.MockClientHttpRequest;
@@ -82,6 +84,15 @@ public class TestRestTemplateTests {
 				.isInstanceOf(HttpComponentsClientHttpRequestFactory.class);
 	}
 
+	@Test
+	public void doNotReplaceCustomRequestFactory() {
+		RestTemplateBuilder builder = new RestTemplateBuilder()
+				.requestFactory(OkHttp3ClientHttpRequestFactory.class);
+		TestRestTemplate testRestTemplate = new TestRestTemplate(builder);
+		assertThat(testRestTemplate.getRestTemplate().getRequestFactory())
+				.isInstanceOf(OkHttp3ClientHttpRequestFactory.class);
+	}
+
 	@Test
 	public void getRootUriRootUriSetViaRestTemplateBuilder() {
 		String rootUri = "http://example.com";
@@ -125,6 +136,7 @@ public class TestRestTemplateTests {
 	@Test
 	public void restOperationsAreAvailable() {
 		RestTemplate delegate = mock(RestTemplate.class);
+		given(delegate.getRequestFactory()).willReturn(new SimpleClientHttpRequestFactory());
 		given(delegate.getUriTemplateHandler())
 				.willReturn(new DefaultUriBuilderFactory());
 		RestTemplateBuilder builder = mock(RestTemplateBuilder.class);