Pre-register default bindings for channels

- This allows resolution of any binding properties specified with `_` instead of `.`
- remove cast and check for ConfigurableEnvironment
- remove the duplicate defaulting channel binding code

Remove unused import

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

@@ -22,7 +22,6 @@ import java.util.Properties;
 
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.boot.context.properties.ConfigurationProperties;
-import org.springframework.util.StringUtils;
 
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonInclude.Include;
@@ -37,9 +36,6 @@ public class ChannelBindingProperties {
 
 	public static final String PATH = "path";
 
-	@Value("${spring.application.name:}")
-	private String applicationName;
-
 	private Properties consumerProperties = new Properties();
 
 	private Properties producerProperties = new Properties();
@@ -85,8 +81,8 @@ public class ChannelBindingProperties {
 				}
 			}
 		}
-		// the default path of the binding is the channel name itself
-		return (StringUtils.hasText(applicationName) ? applicationName + "." : "") + channelName;
+		// just return the channel name if not found
+		return channelName;
 	}
 
 	public String getTapChannelName(String channelName) {

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

@@ -18,11 +18,16 @@ package org.springframework.cloud.stream.config;
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Properties;
 
 import org.springframework.beans.factory.support.BeanDefinitionRegistry;
 import org.springframework.cloud.stream.annotation.EnableModule;
 import org.springframework.cloud.stream.utils.MessageChannelBeanDefinitionRegistryUtils;
+import org.springframework.context.EnvironmentAware;
 import org.springframework.context.annotation.ImportBeanDefinitionRegistrar;
+import org.springframework.core.env.ConfigurableEnvironment;
+import org.springframework.core.env.Environment;
+import org.springframework.core.env.PropertiesPropertySource;
 import org.springframework.core.type.AnnotationMetadata;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.MultiValueMap;
@@ -31,19 +36,36 @@ import org.springframework.util.MultiValueMap;
  * @author Marius Bogoevici
  * @author Dave Syer
  */
-public class ModuleRegistrar implements ImportBeanDefinitionRegistrar {
+public class ModuleRegistrar implements ImportBeanDefinitionRegistrar, EnvironmentAware {
+
+	public static final String SPRING_CLOUD_STREAM_BINDINGS_PREFIX = "spring.cloud.stream.bindings";
+
+	private ConfigurableEnvironment environment;
+
+	@Override
+	public void setEnvironment(Environment environment) {
+		this.environment = (ConfigurableEnvironment) environment;
+	}
 
 	@Override
 	public void registerBeanDefinitions(AnnotationMetadata metadata,
 			BeanDefinitionRegistry registry) {
 		MultiValueMap<String, Object> attributes = metadata.getAllAnnotationAttributes(
 				EnableModule.class.getName(), false);
+		List<String> registeredChannelNames = new ArrayList<>();
 		for (Class<?> type : collectClasses(attributes.get("value"))) {
-			MessageChannelBeanDefinitionRegistryUtils.registerChannelBeanDefinitions(type, registry);
+			registeredChannelNames.addAll(MessageChannelBeanDefinitionRegistryUtils.registerChannelBeanDefinitions(type, registry));
 			MessageChannelBeanDefinitionRegistryUtils.registerChannelsQualifiedBeanDefinitions(
 					ClassUtils.resolveClassName(metadata.getClassName(), null), type,
 					registry);
 		}
+		Properties defaultChannelNameProperties = new Properties();
+		for (String registeredChannelName : registeredChannelNames) {
+			defaultChannelNameProperties.put(SPRING_CLOUD_STREAM_BINDINGS_PREFIX + "." + registeredChannelName,
+					"${spring.application.name:spring.cloud.stream}" + "." + registeredChannelName);
+		}
+		environment.getPropertySources().addLast(
+				new PropertiesPropertySource("default-spring-cloud-stream-channel-bindings", defaultChannelNameProperties));
 	}
 
 	private List<Class<?>> collectClasses(List<Object> list) {

spring-cloud-stream/src/main/java/org/springframework/cloud/stream/utils/MessageChannelBeanDefinitionRegistryUtils.java

@@ -18,6 +18,8 @@ package org.springframework.cloud.stream.utils;
 
 import java.lang.annotation.Annotation;
 import java.lang.reflect.Method;
+import java.util.ArrayList;
+import java.util.List;
 import java.util.Map;
 
 import org.aopalliance.intercept.MethodInterceptor;
@@ -85,8 +87,9 @@ public abstract class MessageChannelBeanDefinitionRegistryUtils {
 		registry.registerBeanDefinition(name, rootBeanDefinition);
 	}
 
-	public static void registerChannelBeanDefinitions(Class<?> type,
+	public static List<String> registerChannelBeanDefinitions(Class<?> type,
 			final BeanDefinitionRegistry registry) {
+		final List<String> channelNames = new ArrayList<>();
 		ReflectionUtils.doWithMethods(type, new MethodCallback() {
 			@Override
 			public void doWith(Method method) throws IllegalArgumentException,
@@ -95,15 +98,18 @@ public abstract class MessageChannelBeanDefinitionRegistryUtils {
 				if (input != null) {
 					String name = getName(input, method);
 					registerInputChannelBeanDefinition(input.value(), name, registry);
+					channelNames.add(name);
 				}
 				Output output = AnnotationUtils.findAnnotation(method, Output.class);
 				if (output != null) {
 					String name = getName(output, method);
 					registerOutputChannelBeanDefinition(output.value(), name, registry);
+					channelNames.add(name);
 				}
 			}
 
 		});
+		return channelNames;
 	}
 
 	public static void registerChannelsQualifiedBeanDefinitions(Class<?> parent, Class<?> type,