added FunctionScan annotation

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

@@ -0,0 +1,46 @@
+/*
+ * Copyright 2017 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.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+import java.util.function.Function;
+
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.context.annotation.FilterType;
+import org.springframework.context.annotation.ComponentScan.Filter;
+
+/**
+ * Annotation that triggers scanning within the specified base packages for
+ * any class that is assignable to {@link Function}. For each detected Function
+ * class, a bean instance will be added to the context. The property key for
+ * providing base packages is: {@code spring.cloud.function.scan.packages}
+ * If no key is provided, the default base package is "functions".
+ *
+ * @author Mark Fisher
+ */
+@Retention(RetentionPolicy.RUNTIME)
+@Target(ElementType.TYPE)
+@Documented
+@ComponentScan(basePackages = "${spring.cloud.function.scan.packages:functions}",
+	includeFilters = @Filter(type = FilterType.ASSIGNABLE_TYPE, classes = Function.class))
+public @interface FunctionScan {
+
+}