Add a sample app with just beans that are Functions

Make it deployable via its maven coordinates in
spring-cloud-function-deployer (it is deployed by default on start
up right now, but that's just a demo)

spring-cloud-function-context/src/main/java/org/springframework/cloud/function/context/ApplicationContextFunctionCatalog.java

@@ -0,0 +1,65 @@
+/*
+ * Copyright 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.cloud.function.context;
+
+import java.util.Map;
+import java.util.function.Consumer;
+import java.util.function.Function;
+import java.util.function.Supplier;
+
+import org.springframework.cloud.function.registry.FunctionCatalog;
+
+public class ApplicationContextFunctionCatalog implements FunctionCatalog {
+
+	private final Map<String, Function<?, ?>> functions;
+	private final Map<String, Consumer<?>> consumers;
+	private final Map<String, Supplier<?>> suppliers;
+
+	public ApplicationContextFunctionCatalog(Map<String, Function<?, ?>> functions,
+			Map<String, Consumer<?>> consumers, Map<String, Supplier<?>> suppliers) {
+		this.functions = functions;
+		this.consumers = consumers;
+		this.suppliers = suppliers;
+	}
+
+	@SuppressWarnings("unchecked")
+	@Override
+	public <T> Consumer<T> lookupConsumer(String name) {
+		return (Consumer<T>) consumers.get(name);
+	}
+
+	@SuppressWarnings("unchecked")
+	@Override
+	public <T, R> Function<T, R> lookupFunction(String name) {
+		return (Function<T, R>) functions.get(name);
+	}
+
+	@Override
+	public <T, R> Function<T, R> composeFunction(String... functionNames) {
+		Function<T, R> function = this.lookupFunction(functionNames[0]);
+		for (int i = 1; i < functionNames.length; i++) {
+			function = function.andThen(this.lookupFunction(functionNames[i]));
+		}
+		return function;
+	}
+
+	@SuppressWarnings("unchecked")
+	@Override
+	public <T> Supplier<T> lookupSupplier(String name) {
+		return (Supplier<T>) suppliers.get(name);
+	}
+
+}

spring-cloud-function-context/src/main/java/org/springframework/cloud/function/context/ContextFunctionCatalogAutoConfiguration.java

@@ -0,0 +1,51 @@
+/*
+ * Copyright 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.cloud.function.context;
+
+import java.util.Collections;
+import java.util.Map;
+import java.util.function.Consumer;
+import java.util.function.Function;
+import java.util.function.Supplier;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.autoconfigure.AutoConfigureBefore;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
+import org.springframework.cloud.function.registry.DefaultFunctionRegistryAutoConfiguration;
+import org.springframework.cloud.function.registry.FunctionCatalog;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+@Configuration
+@ConditionalOnClass(ApplicationContextFunctionCatalog.class)
+@ConditionalOnMissingBean(FunctionCatalog.class)
+@AutoConfigureBefore(DefaultFunctionRegistryAutoConfiguration.class)
+public class ContextFunctionCatalogAutoConfiguration {
+
+	@Autowired(required = false)
+	private Map<String, Function<?, ?>> functions = Collections.emptyMap();
+	@Autowired(required = false)
+	private Map<String, Consumer<?>> consumers = Collections.emptyMap();
+	@Autowired(required = false)
+	private Map<String, Supplier<?>> suppliers = Collections.emptyMap();
+
+	@Bean
+	public FunctionCatalog functionCatalog() {
+		return new ApplicationContextFunctionCatalog(functions, consumers, suppliers);
+	}
+
+}

spring-cloud-function-context/src/main/resources/META-INF/spring.factories

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+org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
+org.springframework.cloud.function.context.ContextFunctionCatalogAutoConfiguration