Configure TestRestTemplate using builder

Update SpringBootTestContextCustomizer to create the TestRestTemplate
using the RestTemplateBuilder whenever possible.

Fixes gh-5509

spring-boot-test/src/main/java/org/springframework/boot/test/context/SpringBootTestContextCustomizer.java

@@ -16,11 +16,19 @@
 
 package org.springframework.boot.test.context;
 
+import org.springframework.beans.BeansException;
+import org.springframework.beans.factory.FactoryBean;
+import org.springframework.beans.factory.NoSuchBeanDefinitionException;
+import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
+import org.springframework.beans.factory.support.BeanDefinitionRegistry;
+import org.springframework.beans.factory.support.RootBeanDefinition;
 import org.springframework.boot.test.web.client.LocalHostUriTemplateHandler;
 import org.springframework.boot.test.web.client.TestRestTemplate;
+import org.springframework.boot.web.client.RestTemplateBuilder;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.ApplicationContextAware;
 import org.springframework.context.ConfigurableApplicationContext;
 import org.springframework.core.annotation.AnnotatedElementUtils;
-import org.springframework.core.env.Environment;
 import org.springframework.test.context.ContextCustomizer;
 import org.springframework.test.context.MergedContextConfiguration;
 
@@ -38,12 +46,24 @@ class SpringBootTestContextCustomizer implements ContextCustomizer {
 		SpringBootTest annotation = AnnotatedElementUtils.getMergedAnnotation(
 				mergedContextConfiguration.getTestClass(), SpringBootTest.class);
 		if (annotation.webEnvironment().isEmbedded()) {
-			Object restTemplate = TestRestTemplateFactory
-					.createRestTemplate(context.getEnvironment());
-			context.getBeanFactory().registerSingleton("testRestTemplate", restTemplate);
+			registerTestRestTemplate(context);
 		}
 	}
 
+	private void registerTestRestTemplate(ConfigurableApplicationContext context) {
+		ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();
+		if (beanFactory instanceof BeanDefinitionRegistry) {
+			registerTestRestTemplate(context, (BeanDefinitionRegistry) context);
+		}
+
+	}
+
+	private void registerTestRestTemplate(ConfigurableApplicationContext context,
+			BeanDefinitionRegistry registry) {
+		registry.registerBeanDefinition("testRestTemplate",
+				new RootBeanDefinition(TestRestTemplateFactory.class));
+	}
+
 	@Override
 	public int hashCode() {
 		return getClass().hashCode();
@@ -57,13 +77,47 @@ class SpringBootTestContextCustomizer implements ContextCustomizer {
 		return true;
 	}
 
-	// Inner class to avoid references to web classes that may not be on the classpath
-	private static class TestRestTemplateFactory {
+	/**
+	 * {@link FactoryBean} used to create a configure a {@link TestRestTemplate}.
+	 */
+	public static class TestRestTemplateFactory
+			implements FactoryBean<TestRestTemplate>, ApplicationContextAware {
 
-		private static TestRestTemplate createRestTemplate(Environment environment) {
-			TestRestTemplate template = new TestRestTemplate();
-			template.setUriTemplateHandler(new LocalHostUriTemplateHandler(environment));
-			return template;
+		private TestRestTemplate object;
+
+		@Override
+		public void setApplicationContext(ApplicationContext applicationContext)
+				throws BeansException {
+			RestTemplateBuilder builder = getRestTemplateBuilder(applicationContext);
+			TestRestTemplate template = new TestRestTemplate(builder.build());
+			template.setUriTemplateHandler(
+					new LocalHostUriTemplateHandler(applicationContext.getEnvironment()));
+			this.object = template;
+		}
+
+		private RestTemplateBuilder getRestTemplateBuilder(
+				ApplicationContext applicationContext) {
+			try {
+				return applicationContext.getBean(RestTemplateBuilder.class);
+			}
+			catch (NoSuchBeanDefinitionException ex) {
+				return new RestTemplateBuilder();
+			}
+		}
+
+		@Override
+		public boolean isSingleton() {
+			return true;
+		}
+
+		@Override
+		public Class<?> getObjectType() {
+			return TestRestTemplate.class;
+		}
+
+		@Override
+		public TestRestTemplate getObject() throws Exception {
+			return this.object;
 		}
 
 	}

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

@@ -91,30 +91,22 @@ public class TestRestTemplate {
 	 */
 	public TestRestTemplate(String username, String password,
 			HttpClientOption... httpClientOptions) {
-		this.restTemplate = createRestTemplate(username, password, httpClientOptions);
+		this(new RestTemplate(), username, password, httpClientOptions);
 	}
 
-	/**
-	 * Factory method used to create the underlying {@link RestTemplate}.
-	 * @param username the username to use (or {@code null})
-	 * @param password the password (or {@code null})
-	 * @param httpClientOptions client options to use if the Apache HTTP Client is used
-	 * @return the delegate {@link RestTemplate}
-	 */
-	protected RestTemplate createRestTemplate(String username, String password,
+	public TestRestTemplate(RestTemplate restTemplate) {
+		this(restTemplate, null, null);
+	}
+
+	public TestRestTemplate(RestTemplate restTemplate, String username, String password,
 			HttpClientOption... httpClientOptions) {
-		RestTemplate restTemplate = new RestTemplate();
+		Assert.notNull(restTemplate, "RestTemplate must not be null");
 		if (ClassUtils.isPresent("org.apache.http.client.config.RequestConfig", null)) {
 			restTemplate.setRequestFactory(
 					new CustomHttpComponentsClientHttpRequestFactory(httpClientOptions));
 		}
 		addAuthentication(restTemplate, username, password);
 		restTemplate.setErrorHandler(new NoOpResponseErrorHandler());
-		return restTemplate;
-	}
-
-	public TestRestTemplate(RestTemplate restTemplate) {
-		Assert.notNull(restTemplate, "RestTemplate must not be null");
 		this.restTemplate = restTemplate;
 	}
 

spring-boot-test/src/test/java/org/springframework/boot/test/context/AbstractSpringBootTestEmbeddedWebEnvironmentTests.java

@@ -60,6 +60,10 @@ public abstract class AbstractSpringBootTestEmbeddedWebEnvironmentTests {
 	@Autowired
 	private TestRestTemplate restTemplate;
 
+	public TestRestTemplate getRestTemplate() {
+		return this.restTemplate;
+	}
+
 	@Test
 	public void runAndTestHttpEndpoint() {
 		assertThat(this.port).isNotEqualTo(8080).isNotEqualTo(0);

spring-boot-test/src/test/java/org/springframework/boot/test/context/SpringBootTestWebEnvironmentRandomPortTests.java

@@ -16,15 +16,21 @@
 
 package org.springframework.boot.test.context;
 
+import org.junit.Test;
 import org.junit.runner.RunWith;
 
 import org.springframework.boot.test.context.SpringBootTest.WebEnvironment;
+import org.springframework.boot.web.client.RestTemplateBuilder;
+import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.http.converter.StringHttpMessageConverter;
 import org.springframework.test.annotation.DirtiesContext;
 import org.springframework.test.context.junit4.SpringRunner;
 import org.springframework.web.bind.annotation.RestController;
 import org.springframework.web.servlet.config.annotation.EnableWebMvc;
 
+import static org.assertj.core.api.Assertions.assertThat;
+
 /**
  * Tests for {@link SpringBootTest} configured with {@link WebEnvironment#RANDOM_PORT}.
  *
@@ -37,11 +43,28 @@ import org.springframework.web.servlet.config.annotation.EnableWebMvc;
 public class SpringBootTestWebEnvironmentRandomPortTests
 		extends AbstractSpringBootTestEmbeddedWebEnvironmentTests {
 
+	@Test
+	public void testRestTemplateShouldUseBuilder() throws Exception {
+		assertThat(getRestTemplate().getRestTemplate().getMessageConverters())
+				.hasAtLeastOneElementOfType(MyConverter.class);
+	}
+
 	@Configuration
 	@EnableWebMvc
 	@RestController
 	protected static class Config extends AbstractConfig {
 
+		@Bean
+		public RestTemplateBuilder restTemplateBuilder() {
+			return new RestTemplateBuilder()
+					.additionalMessageConverters(new MyConverter());
+
+		}
+
+	}
+
+	private static class MyConverter extends StringHttpMessageConverter {
+
 	}
 
 }