Add FunctionRegistry interface (writable FunctionCatalog)

This makes dynamic function registration (after context starts) much
easier. Also frees us from having to employ BeanFactoryPostProcessor
and other tricks to get the functions registered on startup.

spring-cloud-function-context/src/test/java/org/springframework/cloud/function/context/BeanFactoryFunctionCatalogTests.java

@@ -0,0 +1,73 @@
+/*
+ * Copyright 2016-2017 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.util.function.Function;
+
+import org.junit.Test;
+
+import org.springframework.cloud.function.context.ContextFunctionCatalogAutoConfiguration.BeanFactoryFunctionCatalog;
+import org.springframework.cloud.function.context.ContextFunctionCatalogAutoConfiguration.ContextFunctionRegistry;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import reactor.core.publisher.Flux;
+
+/**
+ * @author Dave Syer
+ *
+ */
+public class BeanFactoryFunctionCatalogTests {
+
+	private BeanFactoryFunctionCatalog processor = new BeanFactoryFunctionCatalog(
+			new ContextFunctionRegistry());
+
+	@Test
+	public void basicRegistrationFeatures() {
+		processor.register(new FunctionRegistration<>(new Foos()).names("foos"));
+		Function<Flux<Integer>, Flux<String>> foos = processor.lookupFunction("foos");
+		assertThat(foos.apply(Flux.just(2)).blockFirst()).isEqualTo("4");
+	}
+
+	@Test
+	public void compose() {
+		processor.register(new FunctionRegistration<>(new Foos()).names("foos"));
+		processor.register(new FunctionRegistration<>(new Bars()).names("bars"));
+		Function<Flux<Integer>, Flux<String>> foos = processor
+				.lookupFunction("foos,bars");
+		assertThat(foos.apply(Flux.just(2)).blockFirst()).isEqualTo("Hello 4");
+	}
+
+	protected static class Foos implements Function<Integer, String> {
+
+		@Override
+		public String apply(Integer t) {
+			return "" + 2 * t;
+		}
+
+	}
+
+	protected static class Bars implements Function<String, String> {
+
+		@Override
+		public String apply(String t) {
+			return "Hello " + t;
+		}
+
+	}
+
+}

spring-cloud-function-context/src/test/java/org/springframework/cloud/function/context/ContextFunctionPostProcessorTests.java

@@ -21,7 +21,7 @@ import java.util.function.Function;
 
 import org.junit.Test;
 
-import org.springframework.cloud.function.context.ContextFunctionCatalogAutoConfiguration.ContextFunctionPostProcessor;
+import org.springframework.cloud.function.context.ContextFunctionCatalogAutoConfiguration.ContextFunctionRegistry;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
@@ -31,16 +31,18 @@ import reactor.core.publisher.Flux;
  * @author Dave Syer
  *
  */
+// TODO: test all sorts of error conditions (duplicate registrations, incompatible types
+// for functions with the same name, uncomposable combinations)
 public class ContextFunctionPostProcessorTests {
 
-	private ContextFunctionPostProcessor processor = new ContextFunctionPostProcessor();
+	private ContextFunctionRegistry processor = new ContextFunctionRegistry();
 
 	@Test
 	public void basicRegistrationFeatures() {
 		processor.register(new FunctionRegistration<>(new Foos()).names("foos"));
 		@SuppressWarnings("unchecked")
 		Function<Flux<Integer>, Flux<String>> foos = (Function<Flux<Integer>, Flux<String>>) processor
-				.compose("foos");
+				.lookupFunction("foos");
 		assertThat(foos.apply(Flux.just(2)).blockFirst()).isEqualTo("4");
 	}
 
@@ -52,7 +54,7 @@ public class ContextFunctionPostProcessorTests {
 				Collections.emptyMap(), Collections.emptyMap(), Collections.emptyMap());
 		@SuppressWarnings("unchecked")
 		Function<Flux<Integer>, Flux<String>> foos = (Function<Flux<Integer>, Flux<String>>) processor
-				.compose("foos");
+				.lookupFunction("foos");
 		assertThat(foos.apply(Flux.just(2)).blockFirst()).isEqualTo("4");
 	}
 
@@ -62,7 +64,7 @@ public class ContextFunctionPostProcessorTests {
 				Collections.emptyMap(), Collections.singletonMap("foos", new Foos()));
 		@SuppressWarnings("unchecked")
 		Function<Flux<Integer>, Flux<String>> foos = (Function<Flux<Integer>, Flux<String>>) processor
-				.compose("foos");
+				.lookupFunction("foos");
 		assertThat(foos.apply(Flux.just(2)).blockFirst()).isEqualTo("4");
 	}
 
@@ -72,7 +74,7 @@ public class ContextFunctionPostProcessorTests {
 		processor.register(new FunctionRegistration<>(new Bars()).names("bars"));
 		@SuppressWarnings("unchecked")
 		Function<Flux<Integer>, Flux<String>> foos = (Function<Flux<Integer>, Flux<String>>) processor
-				.compose("foos,bars");
+				.lookupFunction("foos,bars");
 		assertThat(foos.apply(Flux.just(2)).blockFirst()).isEqualTo("Hello 4");
 	}