GH-1272 Removal of parent/child context

Initial removal of parent/child context for Binders. This commit contains bare minimum of what's required while still supporting 'the old way'.
Basically implementor of a binder must do the following things:
- name your configuration file as the usual boot 'spring.factories` (no more spring.binders)
- add name attribute to the `@Bean` which declares the actual binders (e.g., `@Bean('rabbit')`)

This PR ensures that the existing functionality (the use of spring.binders) is preserved.

Resolves #1272
Resolves #1361

polishing

spring-cloud-stream/src/main/java/org/springframework/cloud/stream/binder/DefaultBinderFactory.java

@@ -19,6 +19,7 @@ package org.springframework.cloud.stream.binder;
 import java.util.AbstractMap.SimpleImmutableEntry;
 import java.util.ArrayList;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
@@ -48,6 +49,7 @@ import org.springframework.util.StringUtils;
  * @author Marius Bogoevici
  * @author Ilayaperumal Gopinathan
  * @author Gary Russell
+ * @author Oleg Zhurakousky
  */
 public class DefaultBinderFactory implements BinderFactory, DisposableBean, ApplicationContextAware {
 
@@ -91,8 +93,35 @@ public class DefaultBinderFactory implements BinderFactory, DisposableBean, Appl
 		this.defaultBinderForBindingTargetType.clear();
 	}
 
+	@SuppressWarnings({"unchecked", "rawtypes"})
 	@Override
 	public synchronized <T> Binder<T, ?, ?> getBinder(String name, Class<? extends T> bindingTargetType) {
+
+		String binderName = StringUtils.hasText(name) ? name : this.defaultBinder;
+
+		Map<String, Binder> binders = this.context == null ? Collections.emptyMap() : this.context.getBeansOfType(Binder.class);
+		Binder<T, ConsumerProperties, ProducerProperties> binder;
+		if (StringUtils.hasText(binderName) && binders.containsKey(binderName)) {
+			binder = (Binder<T, ConsumerProperties, ProducerProperties>) this.context.getBean(binderName);
+		}
+		else if (binders.size() == 1) {
+			binder = binders.values().iterator().next();
+		}
+		else  if (binders.size() > 1) {
+			throw new IllegalStateException("Multiple binders are available, however neither default nor "
+					+ "per-destination binder name is provided. Available binders are " + binders.keySet());
+		}
+		else {
+			/*
+			 * This is the fall back to the old bootstrap that relies on spring.binders.
+			 */
+			binder = this.doGetBinder(binderName, bindingTargetType);
+		}
+		return binder;
+	}
+
+
+	private <T> Binder<T, ConsumerProperties, ProducerProperties> doGetBinder(String name, Class<? extends T> bindingTargetType) {
 		String configurationName;
 		// Fall back to a default if no argument is provided
 		if (StringUtils.isEmpty(name)) {
@@ -136,7 +165,7 @@ public class DefaultBinderFactory implements BinderFactory, DisposableBean, Appl
 		else {
 			configurationName = name;
 		}
-		Binder<T, ?, ?> binderInstance = getBinderInstance(configurationName);
+		Binder<T, ConsumerProperties, ProducerProperties> binderInstance = getBinderInstance(configurationName);
 		Assert.state(verifyBinderTypeMatchesTarget(binderInstance, bindingTargetType),
 				"The binder '" + configurationName + "' cannot bind a " + bindingTargetType.getName());
 		return binderInstance;
@@ -159,7 +188,7 @@ public class DefaultBinderFactory implements BinderFactory, DisposableBean, Appl
 	}
 
 	@SuppressWarnings("unchecked")
-	private <T> Binder<T, ?, ?> getBinderInstance(String configurationName) {
+	private <T> Binder<T, ConsumerProperties, ProducerProperties> getBinderInstance(String configurationName) {
 		if (!this.binderInstanceCache.containsKey(configurationName)) {
 			BinderConfiguration binderConfiguration = this.binderConfigurations.get(configurationName);
 			Assert.state(binderConfiguration != null, "Unknown binder configuration: " + configurationName);
@@ -212,7 +241,7 @@ public class DefaultBinderFactory implements BinderFactory, DisposableBean, Appl
 			}
 			this.binderInstanceCache.put(configurationName, new SimpleImmutableEntry<>(binder, binderProducingContext));
 		}
-		return (Binder<T, ?, ?>) this.binderInstanceCache.get(configurationName).getKey();
+		return (Binder<T, ConsumerProperties, ProducerProperties>) this.binderInstanceCache.get(configurationName).getKey();
 	}
 
 	/**

spring-cloud-stream/src/main/java/org/springframework/cloud/stream/config/BinderFactoryConfiguration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2015-2017 the original author or authors.
+ * Copyright 2015-2018 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.
@@ -27,6 +27,9 @@ import java.util.List;
 import java.util.Map;
 import java.util.Properties;
 
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+
 import org.springframework.beans.factory.BeanCreationException;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.beans.factory.annotation.Value;
@@ -52,11 +55,14 @@ import org.springframework.util.StringUtils;
 /**
  * @author Marius Bogoevici
  * @author Ilayaperumal Gopinathan
+ * @author Oleg Zhurakousky
  */
 @Configuration
 @Role(BeanDefinition.ROLE_INFRASTRUCTURE)
 public class BinderFactoryConfiguration {
 
+	protected final Log logger = LogFactory.getLog(getClass());
+
 	private static final String SPRING_CLOUD_STREAM_INTERNAL_PREFIX = "spring.cloud.stream.internal";
 
 	private static final String SELF_CONTAINED_APP_PROPERTY_NAME = SPRING_CLOUD_STREAM_INTERNAL_PREFIX
@@ -150,16 +156,19 @@ public class BinderFactoryConfiguration {
 		try {
 			Enumeration<URL> resources = classLoader.getResources("META-INF/spring.binders");
 			if (!Boolean.valueOf(this.selfContained) && (resources == null || !resources.hasMoreElements())) {
-				throw new BeanCreationException("Cannot create binder factory, no `META-INF/spring.binders` " +
-						"resources found on the classpath");
+				this.logger.debug("Failed to locate 'META-INF/spring.binders' resources on the classpath."
+						+ " Assuming standard boot 'META-INF/spring.factories' configuration is used");
 			}
-			while (resources.hasMoreElements()) {
-				URL url = resources.nextElement();
-				UrlResource resource = new UrlResource(url);
-				for (BinderType binderType : parseBinderConfigurations(classLoader, resource)) {
-					binderTypes.put(binderType.getDefaultName(), binderType);
+			else {
+				while (resources.hasMoreElements()) {
+					URL url = resources.nextElement();
+					UrlResource resource = new UrlResource(url);
+					for (BinderType binderType : parseBinderConfigurations(classLoader, resource)) {
+						binderTypes.put(binderType.getDefaultName(), binderType);
+					}
 				}
 			}
+
 		}
 		catch (IOException | ClassNotFoundException e) {
 			throw new BeanCreationException("Cannot create binder factory:", e);

spring-cloud-stream/src/test/java/org/springframework/cloud/stream/binder/BinderFactoryConfigurationTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2015-2017 the original author or authors.
+ * Copyright 2015-2018 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.
@@ -22,7 +22,6 @@ import java.net.URLClassLoader;
 
 import org.junit.Test;
 
-import org.springframework.beans.factory.BeanCreationException;
 import org.springframework.boot.WebApplicationType;
 import org.springframework.boot.autoconfigure.context.PropertyPlaceholderAutoConfiguration;
 import org.springframework.boot.builder.SpringApplicationBuilder;
@@ -82,33 +81,6 @@ public class BinderFactoryConfigurationTests {
 				.run();
 	}
 
-	@Test
-	public void loadBinderTypeRegistry() throws Exception {
-		try {
-			createBinderTestContext(new String[] {});
-			fail();
-		}
-		catch (BeanCreationException e) {
-			assertThat(e.getMessage()).contains(
-					"Cannot create binder factory, no `META-INF/spring.binders` resources found on the classpath");
-		}
-	}
-
-	@Test
-	public void loadBinderTypeRegistryWithNonSelfContainedAggregatorApp() throws Exception {
-		try {
-			createBinderTestContextWithSources(
-					new Class[] { SimpleApplication.class }, new String[] {},
-					"spring.cloud.stream.internal.selfContained=false");
-			fail();
-		}
-		catch (BeanCreationException e) {
-			assertThat(e.getMessage()).contains(
-					"Cannot create binder factory, no `META-INF/spring.binders` resources found on the classpath");
-		}
-
-	}
-
 	@Test
 	public void loadBinderTypeRegistryWithSelfContainedAggregatorApp() throws Exception {
 		createBinderTestContextWithSources(