Provide web client Auto-configuration

Add auto-configuration for use with typical web clients. Currently
client auto-configuration consists of a RestTemplateBuilder
pre-configured with HttpMessageConverters.

Closes gh-5507

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/WebClientAutoConfiguration.java

@@ -0,0 +1,81 @@
+/*
+ * Copyright 2012-2016 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.autoconfigure.web;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.springframework.beans.factory.ObjectProvider;
+import org.springframework.boot.autoconfigure.AutoConfigureAfter;
+import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
+import org.springframework.boot.web.client.RestTemplateBuilder;
+import org.springframework.boot.web.client.RestTemplateCustomizer;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.core.annotation.AnnotationAwareOrderComparator;
+import org.springframework.util.CollectionUtils;
+import org.springframework.web.client.RestTemplate;
+
+/**
+ * {@link EnableAutoConfiguration Auto-configuration} for web client.
+ *
+ * @author Stephane Nicoll
+ * @author Phillip Webb
+ * @since 1.4.0
+ */
+@Configuration
+@AutoConfigureAfter(HttpMessageConvertersAutoConfiguration.class)
+public class WebClientAutoConfiguration {
+
+	@Configuration
+	@ConditionalOnClass(RestTemplate.class)
+	public static class RestTemplateConfiguration {
+
+		private final ObjectProvider<HttpMessageConverters> messageConverters;
+
+		private final ObjectProvider<List<RestTemplateCustomizer>> restTemplateCustomizers;
+
+		public RestTemplateConfiguration(
+				ObjectProvider<HttpMessageConverters> messageConverters,
+				ObjectProvider<List<RestTemplateCustomizer>> restTemplateCustomizers) {
+			this.messageConverters = messageConverters;
+			this.restTemplateCustomizers = restTemplateCustomizers;
+		}
+
+		@Bean
+		@ConditionalOnMissingBean
+		public RestTemplateBuilder restTemplateBuilder() {
+			RestTemplateBuilder builder = new RestTemplateBuilder();
+			HttpMessageConverters converters = this.messageConverters.getIfUnique();
+			if (converters != null) {
+				builder = builder.messageConverters(converters.getConverters());
+			}
+			List<RestTemplateCustomizer> customizers = this.restTemplateCustomizers
+					.getIfAvailable();
+			if (!CollectionUtils.isEmpty(customizers)) {
+				customizers = new ArrayList<RestTemplateCustomizer>(customizers);
+				AnnotationAwareOrderComparator.sort(customizers);
+				builder = builder.customizers(customizers);
+			}
+			return builder;
+		}
+
+	}
+
+}

spring-boot-autoconfigure/src/main/resources/META-INF/spring.factories

@@ -94,6 +94,7 @@ org.springframework.boot.autoconfigure.web.HttpEncodingAutoConfiguration,\
 org.springframework.boot.autoconfigure.web.HttpMessageConvertersAutoConfiguration,\
 org.springframework.boot.autoconfigure.web.MultipartAutoConfiguration,\
 org.springframework.boot.autoconfigure.web.ServerPropertiesAutoConfiguration,\
+org.springframework.boot.autoconfigure.web.WebClientAutoConfiguration,\
 org.springframework.boot.autoconfigure.web.WebMvcAutoConfiguration,\
 org.springframework.boot.autoconfigure.websocket.WebSocketAutoConfiguration,\
 org.springframework.boot.autoconfigure.websocket.WebSocketMessagingAutoConfiguration,\

spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/WebClientAutoConfigurationTests.java

@@ -0,0 +1,192 @@
+/*
+ * Copyright 2012-2016 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.autoconfigure.web;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.junit.After;
+import org.junit.Test;
+
+import org.springframework.boot.web.client.RestTemplateBuilder;
+import org.springframework.boot.web.client.RestTemplateCustomizer;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.http.client.HttpComponentsClientHttpRequestFactory;
+import org.springframework.http.converter.HttpMessageConverter;
+import org.springframework.http.converter.StringHttpMessageConverter;
+import org.springframework.web.client.RestTemplate;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+
+/**
+ * Tests for {@link WebClientAutoConfiguration}
+ *
+ * @author Stephane Nicoll
+ * @author Phillip Webb
+ */
+public class WebClientAutoConfigurationTests {
+
+	private AnnotationConfigApplicationContext context;
+
+	@After
+	public void close() {
+		if (this.context != null) {
+			this.context.close();
+		}
+	}
+
+	@Test
+	public void restTemplateWhenMessageConvertersDefinedShouldHaveMessageConverters() {
+		load(HttpMessageConvertersAutoConfiguration.class, RestTemplateConfig.class);
+		assertThat(this.context.getBeansOfType(RestTemplate.class)).hasSize(1);
+		RestTemplate restTemplate = this.context.getBean(RestTemplate.class);
+		List<HttpMessageConverter<?>> converters = this.context
+				.getBean(HttpMessageConverters.class).getConverters();
+		assertThat(restTemplate.getMessageConverters())
+				.containsExactlyElementsOf(converters);
+		assertThat(restTemplate.getRequestFactory())
+				.isInstanceOf(HttpComponentsClientHttpRequestFactory.class);
+	}
+
+	@Test
+	public void restTemplateWhenNoMessageConvertersDefinedShouldHaveDefaultMessageConverters() {
+		load(RestTemplateConfig.class);
+		RestTemplate restTemplate = this.context.getBean(RestTemplate.class);
+		assertThat(restTemplate.getMessageConverters().size())
+				.isEqualTo(new RestTemplate().getMessageConverters().size());
+	}
+
+	@Test
+	public void restTemplateWhenHasCustomMesssageConvertersShouldHaveMessageConverters() {
+		load(CustomHttpMessageConverter.class,
+				HttpMessageConvertersAutoConfiguration.class, RestTemplateConfig.class);
+		RestTemplate restTemplate = this.context.getBean(RestTemplate.class);
+		List<Class<?>> converterClasses = new ArrayList<Class<?>>();
+		for (HttpMessageConverter<?> converter : restTemplate.getMessageConverters()) {
+			converterClasses.add(converter.getClass());
+		}
+		assertThat(converterClasses).contains(CustomHttpMessageConverter.class);
+	}
+
+	@Test
+	public void restTemplateWhenHasCustomBuilderShouldUseCustomBuilder() {
+		load(RestTemplateConfig.class, CustomRestTemplateBuilderConfig.class);
+		assertThat(this.context.getBeansOfType(RestTemplate.class)).hasSize(1);
+		RestTemplate restTemplate = this.context.getBean(RestTemplate.class);
+		assertThat(restTemplate.getMessageConverters()).hasSize(1);
+		assertThat(restTemplate.getMessageConverters().get(0))
+				.isInstanceOf(CustomHttpMessageConverter.class);
+	}
+
+	@Test
+	public void restTemplateShouldApplyCustomizer() throws Exception {
+		load(RestTemplateCustomizerConfig.class, RestTemplateConfig.class);
+		RestTemplate restTemplate = this.context.getBean(RestTemplate.class);
+		RestTemplateCustomizer customizer = this.context
+				.getBean(RestTemplateCustomizer.class);
+		verify(customizer).customize(restTemplate);
+	}
+
+	@Test
+	public void builderShouldBeFreshForEachUse() throws Exception {
+		load(DirtyRestTemplateConfig.class);
+	}
+
+	public void load(Class<?>... config) {
+		AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext();
+		ctx.register(config);
+		ctx.register(WebClientAutoConfiguration.class);
+		ctx.refresh();
+		this.context = ctx;
+	}
+
+	@Configuration
+	static class RestTemplateConfig {
+
+		@Bean
+		public RestTemplate restTemplate(RestTemplateBuilder builder) {
+			return builder.build();
+		}
+
+	}
+
+	@Configuration
+	static class DirtyRestTemplateConfig {
+
+		@Bean
+		public RestTemplate restTemplateOne(RestTemplateBuilder builder) {
+			try {
+				return builder.build();
+			}
+			finally {
+				breakBuilderOnNextCall(builder);
+			}
+		}
+
+		@Bean
+		public RestTemplate restTemplateTwo(RestTemplateBuilder builder) {
+			try {
+				return builder.build();
+			}
+			finally {
+				breakBuilderOnNextCall(builder);
+			}
+		}
+
+		private void breakBuilderOnNextCall(RestTemplateBuilder builder) {
+			builder.additionalCustomizers(new RestTemplateCustomizer() {
+
+				@Override
+				public void customize(RestTemplate restTemplate) {
+					throw new IllegalStateException();
+				}
+
+			});
+		}
+
+	}
+
+	@Configuration
+	static class CustomRestTemplateBuilderConfig {
+
+		@Bean
+		public RestTemplateBuilder restTemplateBuilder() {
+			return new RestTemplateBuilder()
+					.messageConverters(new CustomHttpMessageConverter());
+		}
+
+	}
+
+	@Configuration
+	static class RestTemplateCustomizerConfig {
+
+		@Bean
+		public RestTemplateCustomizer restTemplateCustomizer() {
+			return mock(RestTemplateCustomizer.class);
+		}
+
+	}
+
+	static class CustomHttpMessageConverter extends StringHttpMessageConverter {
+
+	}
+
+}