Gh 586 loadbalancer starter (#599)

* Add loadbalancer starter. Add property to set BlockingLoadBalancerClient
as default non-reactive loadbalancer. Start working on auto-enabling caching.

* Automatically enable caching. Fixes gh-585.

* Add tests.

* Add reference docs.

* Change property name.

spring-cloud-loadbalancer/src/main/java/org/springframework/cloud/loadbalancer/config/BlockingLoadBalancerClientAutoConfiguration.java

@@ -23,17 +23,20 @@ import org.apache.commons.logging.LogFactory;
 
 import org.springframework.boot.autoconfigure.AutoConfigureAfter;
 import org.springframework.boot.autoconfigure.AutoConfigureBefore;
+import org.springframework.boot.autoconfigure.condition.AnyNestedCondition;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
-import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingClass;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
 import org.springframework.cloud.client.loadbalancer.AsyncLoadBalancerAutoConfiguration;
 import org.springframework.cloud.client.loadbalancer.LoadBalancerClient;
 import org.springframework.cloud.loadbalancer.annotation.LoadBalancerClients;
 import org.springframework.cloud.loadbalancer.blocking.client.BlockingLoadBalancerClient;
 import org.springframework.cloud.loadbalancer.support.LoadBalancerClientFactory;
 import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Conditional;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Primary;
 import org.springframework.web.client.RestTemplate;
 
 /**
@@ -60,13 +63,32 @@ public class BlockingLoadBalancerClientAutoConfiguration {
 	@Bean
 	@ConditionalOnBean(LoadBalancerClientFactory.class)
 	@ConditionalOnClass(RestTemplate.class)
-	@ConditionalOnMissingBean
-	@ConditionalOnMissingClass("org.springframework.cloud.netflix.ribbon.RibbonLoadBalancerClient")
-	public LoadBalancerClient loadBalancerClient(
+	@Conditional(OnNoRibbonDefaultCondition.class)
+	@Primary
+	public LoadBalancerClient blockingLoadBalancerClient(
 			LoadBalancerClientFactory loadBalancerClientFactory) {
 		return new BlockingLoadBalancerClient(loadBalancerClientFactory);
 	}
 
+	private static final class OnNoRibbonDefaultCondition extends AnyNestedCondition {
+
+		private OnNoRibbonDefaultCondition() {
+			super(ConfigurationPhase.REGISTER_BEAN);
+		}
+
+		@ConditionalOnProperty(value = "spring.cloud.loadbalancer.ribbon.enabled",
+				havingValue = "false")
+		static class RibbonNotEnabled {
+
+		}
+
+		@ConditionalOnMissingClass("org.springframework.cloud.netflix.ribbon.RibbonLoadBalancerClient")
+		static class RibbonLoadBalancerNotPresent {
+
+		}
+
+	}
+
 }
 
 class RibbonWarnLogger {
@@ -79,7 +101,8 @@ class RibbonWarnLogger {
 			LOG.warn(
 					"You already have RibbonLoadBalancerClient on your classpath. It will be used by default. To use "
 							+ BlockingLoadBalancerClient.class.getSimpleName()
-							+ " remove spring-cloud-starter-netflix-ribbon from your project.");
+							+ " set the value of `spring.cloud.loadbalancer.ribbon.enabled` to `false` or "
+							+ "remove spring-cloud-starter-netflix-ribbon from your project.");
 		}
 	}
 

spring-cloud-loadbalancer/src/main/java/org/springframework/cloud/loadbalancer/config/LoadBalancerCacheAutoConfiguration.java

@@ -0,0 +1,44 @@
+/*
+ * Copyright 2012-2019 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.loadbalancer.config;
+
+import org.springframework.boot.autoconfigure.AutoConfigureBefore;
+import org.springframework.boot.autoconfigure.cache.CacheAutoConfiguration;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
+import org.springframework.cache.CacheManager;
+import org.springframework.cache.annotation.EnableCaching;
+import org.springframework.cache.interceptor.CacheAspectSupport;
+import org.springframework.context.annotation.Configuration;
+
+/**
+ * An AutoConfiguration that automatically enables caching when when Spring Boot and
+ * Spring Framework Cache support classes are present.
+ *
+ * @author Olga Maciaszek-Sharma
+ * @see CacheManager
+ * @see CacheAutoConfiguration
+ * @see CacheAspectSupport
+ */
+@Configuration
+@ConditionalOnClass({ CacheManager.class, CacheAutoConfiguration.class })
+@ConditionalOnMissingBean(CacheAspectSupport.class)
+@EnableCaching
+@AutoConfigureBefore(CacheAutoConfiguration.class)
+public class LoadBalancerCacheAutoConfiguration {
+
+}

spring-cloud-loadbalancer/src/main/resources/META-INF/spring.factories

@@ -1,4 +1,5 @@
 # AutoConfiguration
 org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
 org.springframework.cloud.loadbalancer.config.LoadBalancerAutoConfiguration,\
-org.springframework.cloud.loadbalancer.config.BlockingLoadBalancerClientAutoConfiguration
+org.springframework.cloud.loadbalancer.config.BlockingLoadBalancerClientAutoConfiguration,\
+org.springframework.cloud.loadbalancer.config.LoadBalancerCacheAutoConfiguration

spring-cloud-loadbalancer/src/test/java/org/springframework/cloud/loadbalancer/config/LoadBalancerCacheAutoConfigurationTests.java

@@ -0,0 +1,70 @@
+/*
+ * Copyright 2012-2019 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.loadbalancer.config;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.boot.autoconfigure.cache.CacheAutoConfiguration;
+import org.springframework.boot.test.util.TestPropertyValues;
+import org.springframework.cache.CacheManager;
+import org.springframework.cache.support.NoOpCacheManager;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+import org.springframework.util.StringUtils;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link LoadBalancerCacheAutoConfiguration}.
+ *
+ * @author Olga Maciaszek-Sharma
+ */
+
+class LoadBalancerCacheAutoConfigurationTests {
+
+	@Test
+	void shouldAutoEnableCaching() {
+		AnnotationConfigApplicationContext context = setup("");
+		assertThat(context.getBeansOfType(CacheManager.class)).isNotEmpty();
+		assertThat(context.getBeansOfType(CacheManager.class).get("cacheManager"))
+				.isNotInstanceOf(NoOpCacheManager.class);
+	}
+
+	@Test
+	void shouldUseNoOpCacheIfCacheTypeNone() {
+		AnnotationConfigApplicationContext context = setup("spring.cache.type=none");
+		assertThat(context.getBeansOfType(CacheManager.class)).isNotEmpty();
+		assertThat(context.getBeansOfType(CacheManager.class).get("cacheManager"))
+				.isInstanceOf(NoOpCacheManager.class);
+	}
+
+	private AnnotationConfigApplicationContext setup(String property) {
+		List<Class> config = new ArrayList<>();
+		config.add(LoadBalancerCacheAutoConfiguration.class);
+		config.add(CacheAutoConfiguration.class);
+		AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
+		if (StringUtils.hasText(property)) {
+			TestPropertyValues.of(property).applyTo(context);
+		}
+		context.register(config.toArray(new Class[0]));
+		context.refresh();
+		return context;
+	}
+
+}