GH-1773 Added support for native spring.cloud.function.definition property

Resolves #1773

docs/src/main/asciidoc/spring-cloud-stream.adoc

@@ -591,7 +591,7 @@ Since Spring Cloud Stream v2.1, another alternative for defining _stream handler
 support for https://cloud.spring.io/spring-cloud-function/[Spring Cloud Function] where they can be expressed as beans of
  type `java.util.function.[Supplier/Function/Consumer]`.
 
-To specify which functional bean to bind to the external destination(s) exposed by the bindings, you must provide `spring.cloud.stream.function.definition` property.
+To specify which functional bean to bind to the external destination(s) exposed by the bindings, you must provide `spring.cloud.stream.function.definition` or native to spring-cloud-function `spring.cloud.function.definition` property.
 
 Here is the example of the Processor application exposing message handler as `java.util.function.Function`
 [source,java]
@@ -601,7 +601,7 @@ Here is the example of the Processor application exposing message handler as `ja
 public class MyFunctionBootApp {
 
 	public static void main(String[] args) {
-		SpringApplication.run(MyFunctionBootApp.class, "--spring.cloud.stream.function.definition=toUpperCase");
+		SpringApplication.run(MyFunctionBootApp.class, "--spring.cloud.function.definition=toUpperCase");
 	}
 
 	@Bean

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

@@ -288,6 +288,9 @@ public class BinderFactoryAutoConfiguration {
 
 	private String determineFunctionName(FunctionCatalog catalog, Environment environment) {
 		String name = environment.getProperty("spring.cloud.stream.function.definition");
+		if (!StringUtils.hasText(name)) {
+			name = environment.getProperty("spring.cloud.function.definition");
+		}
 		if (!StringUtils.hasText(name) && Boolean.parseBoolean(
 				environment.getProperty("spring.cloud.function.routing.enabled", "false"))) {
 			name = RoutingFunction.FUNCTION_NAME;

spring-cloud-stream/src/test/java/org/springframework/cloud/stream/function/ImplicitFunctionBindingTests.java

@@ -19,6 +19,7 @@ package org.springframework.cloud.stream.function;
 import java.util.function.Consumer;
 import java.util.function.Function;
 
+import org.junit.After;
 import org.junit.Test;
 import reactor.core.publisher.Flux;
 
@@ -46,6 +47,12 @@ import static org.assertj.core.api.Assertions.assertThat;
  */
 public class ImplicitFunctionBindingTests {
 
+	@After
+	public void after() {
+		System.clearProperty("spring.cloud.stream.function.definition");
+		System.clearProperty("spring.cloud.function.definition");
+	}
+
 	@Test
 	public void testBindingWithNoEnableBindingConfiguration() {
 
@@ -70,6 +77,30 @@ public class ImplicitFunctionBindingTests {
 		}
 	}
 
+	@Test
+	public void testBindingWithNoEnableBindingConfigurationWithFunctionNativeDefinitionProperty() {
+
+		try (ConfigurableApplicationContext context = new SpringApplicationBuilder(
+				TestChannelBinderConfiguration.getCompleteConfiguration(
+						NoEnableBindingConfiguration.class))
+								.web(WebApplicationType.NONE)
+								.run("--spring.jmx.enabled=false",
+										"--spring.cloud.function.definition=func")) {
+
+			InputDestination inputDestination = context.getBean(InputDestination.class);
+			OutputDestination outputDestination = context
+					.getBean(OutputDestination.class);
+
+			Message<byte[]> inputMessage = MessageBuilder
+					.withPayload("Hello".getBytes()).build();
+			inputDestination.send(inputMessage);
+
+			Message<byte[]> outputMessage = outputDestination.receive();
+			assertThat(outputMessage.getPayload()).isEqualTo("Hello".getBytes());
+
+		}
+	}
+
 	@Test
 	public void testBindingWithEnableBindingConfiguration() {