Fix Build and upgrade fully to Boot 2.0

Some tests still ignored.

Also adds draft functional bean registration support. The AWS sample
is using that now (it starts up 4x faster in AWS). To activate the
functional beans user has to supply a main class of type
ApplicationContextInitializer.

spring-cloud-function-adapters/spring-cloud-function-adapter-aws/src/main/java/org/springframework/cloud/function/adapter/aws/SpringFunctionInitializer.java

@@ -33,9 +33,12 @@ import org.reactivestreams.Publisher;
 
 import org.springframework.beans.BeanUtils;
 import org.springframework.beans.factory.annotation.Autowired;
-import org.springframework.boot.builder.SpringApplicationBuilder;
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.WebApplicationType;
 import org.springframework.cloud.function.context.FunctionCatalog;
 import org.springframework.cloud.function.context.catalog.FunctionInspector;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.ApplicationContextInitializer;
 import org.springframework.context.ConfigurableApplicationContext;
 import org.springframework.util.ClassUtils;
 
@@ -87,8 +90,8 @@ public class SpringFunctionInitializer implements Closeable {
 			return;
 		}
 		logger.info("Initializing: " + configurationClass);
-		SpringApplicationBuilder builder = springApplication();
-		ConfigurableApplicationContext context = builder.web(false).run();
+		SpringApplication builder = springApplication();
+		ConfigurableApplicationContext context = builder.run();
 		context.getAutowireCapableBeanFactory().autowireBean(this);
 		String name = context.getEnvironment().getProperty("function.name");
 		boolean defaultName = false;
@@ -121,17 +124,27 @@ public class SpringFunctionInitializer implements Closeable {
 
 	}
 
-	private SpringApplicationBuilder springApplication() {
-		if (ClassUtils.hasConstructor(SpringApplicationBuilder.class, Object[].class)) {
-			SpringApplicationBuilder builder = new SpringApplicationBuilder(
-					configurationClass);
-			return builder;
+	private SpringApplication springApplication() {
+		ApplicationContextInitializer<?> initializer = null;
+		Class<?> sourceClass = configurationClass;
+		if (ApplicationContextInitializer.class.isAssignableFrom(sourceClass)) {
+			initializer = BeanUtils.instantiateClass(configurationClass, ApplicationContextInitializer.class);
+			sourceClass = Object.class;
 		}
-		// Forward compatibility with Spring Boot 2.0 via reflection
-		return BeanUtils.instantiateClass(
-				ClassUtils.getConstructorIfAvailable(SpringApplicationBuilder.class,
-						Class[].class),
-				new Object[] { new Class<?>[] { configurationClass } });
+		SpringApplication application;
+		if (initializer!=null) {
+			application = new SpringApplication(sourceClass) {
+				@Override
+				protected void load(ApplicationContext context, Object[] sources) {
+				}
+			};
+			application.addInitializers(initializer);
+			application.setDefaultProperties(Collections.singletonMap("spring.functional.enabled", "true"));
+		} else {
+			application = new SpringApplication(sourceClass);
+		}
+		application.setWebApplicationType(WebApplicationType.NONE);
+		return application;
 	}
 
 	protected Class<?> getInputType() {

spring-cloud-function-adapters/spring-cloud-function-adapter-aws/src/test/java/org/springframework/cloud/function/adapter/aws/SpringFunctionInitializerTests.java

@@ -24,10 +24,14 @@ import java.util.stream.Collectors;
 import org.junit.After;
 import org.junit.Test;
 
+import org.springframework.cloud.function.context.FunctionRegistration;
+import org.springframework.cloud.function.context.FunctionType;
 import org.springframework.cloud.function.context.config.ContextFunctionCatalogAutoConfiguration;
+import org.springframework.context.ApplicationContextInitializer;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Import;
+import org.springframework.context.support.GenericApplicationContext;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
@@ -65,6 +69,14 @@ public class SpringFunctionInitializerTests {
 		assertThat(result.blockFirst()).isInstanceOf(Bar.class);
 	}
 
+	@Test
+	public void functionRegistrar() {
+		initializer = new SpringFunctionInitializer(FunctionRegistrar.class);
+		initializer.initialize();
+		Flux<?> result = Flux.from(initializer.apply(Flux.just(new Foo())));
+		assertThat(result.blockFirst()).isInstanceOf(Bar.class);
+	}
+
 	@Test
 	public void namedFunctionCatalog() {
 		initializer = new SpringFunctionInitializer(NamedFunctionConfig.class);
@@ -98,6 +110,23 @@ public class SpringFunctionInitializerTests {
 		}
 	}
 
+	protected static class FunctionRegistrar
+			implements ApplicationContextInitializer<GenericApplicationContext> {
+
+		public Function<Flux<Foo>, Flux<Bar>> function() {
+			return flux -> flux.map(foo -> new Bar());
+		}
+
+		@Override
+		public void initialize(GenericApplicationContext context) {
+			context.registerBean("function", FunctionRegistration.class,
+					() -> new FunctionRegistration<Function<Flux<Foo>, Flux<Bar>>>(
+							function()).name("function")
+									.type(FunctionType.from(Foo.class).to(Bar.class)
+											.wrap(Flux.class).getType()));
+		}
+	}
+
 	@Configuration
 	@Import(ContextFunctionCatalogAutoConfiguration.class)
 	protected static class FunctionConfig {