GH-1104 Add support for case insensitive routing header names

Resolves #1104

Author: olegz

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

@@ -17,6 +17,7 @@
 package org.springframework.cloud.function.context.config;
 
 import java.util.Map;
+import java.util.Map.Entry;
 import java.util.function.Function;
 
 import org.apache.commons.logging.Log;
@@ -133,14 +134,8 @@ private Object route(Object input, boolean originalInputIsPublisher) {
 				}
 			}
 			if (function == null) {
-				if (StringUtils.hasText((String) message.getHeaders().get(FunctionProperties.FUNCTION_DEFINITION))) {
-					function = functionFromDefinition((String) message.getHeaders().get(FunctionProperties.FUNCTION_DEFINITION));
-					if (function.isInputTypePublisher()) {
-						this.assertOriginalInputIsNotPublisher(originalInputIsPublisher);
-					}
-				}
-				else if (StringUtils.hasText((String) message.getHeaders().get(FunctionProperties.ROUTING_EXPRESSION))) {
-					function = this.functionFromExpression((String) message.getHeaders().get(FunctionProperties.ROUTING_EXPRESSION), message, true);
+				function = this.locateFunctionFromDefinitionOrExpression(message);
+				if (function != null) {
 					if (function.isInputTypePublisher()) {
 						this.assertOriginalInputIsNotPublisher(originalInputIsPublisher);
 					}
@@ -196,6 +191,18 @@ else if (StringUtils.hasText(functionProperties.getRoutingExpression())) {
 		return function.apply(input);
 	}
 
+	private FunctionInvocationWrapper locateFunctionFromDefinitionOrExpression(Message<?> message) {
+		for (Entry<String, Object> headerEntry : message.getHeaders().entrySet()) {
+			if (headerEntry.getKey().equalsIgnoreCase(FunctionProperties.FUNCTION_DEFINITION)) {
+				return functionFromDefinition((String) headerEntry.getValue());
+			}
+			else if (headerEntry.getKey().equalsIgnoreCase(FunctionProperties.ROUTING_EXPRESSION)) {
+				return this.functionFromExpression((String) headerEntry.getValue(), message, true);
+			}
+		}
+		return null;
+	}
+
 	private void assertOriginalInputIsNotPublisher(boolean originalInputIsPublisher) {
 		Assert.isTrue(!originalInputIsPublisher, "Routing input of type Publisher is not supported per individual "
 				+ "values (e.g., message header or POJO). Instead you should use 'spring.cloud.function.definition' or "

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

@@ -266,6 +266,16 @@ public void testMultipleRouters() {
 		assertThat(function.apply(message)).isEqualTo("olleh");
 	}
 
+	@SuppressWarnings({ "rawtypes", "unchecked" })
+	@Test
+	public void testMultipleRoutersCaseInsensitiveKeys() {
+		FunctionCatalog functionCatalog = this.configureCatalog(MultipleRouterConfiguration.class);
+		Function function = functionCatalog.lookup(RoutingFunction.FUNCTION_NAME);
+		assertThat(function).isNotNull();
+		Message<String> message = MessageBuilder.withPayload("hello").setHeader(FunctionProperties.PREFIX + ".DeFiNition", "uppercase").build();
+		assertThat(function.apply(message)).isEqualTo("HELLO");
+	}
+
 	@EnableAutoConfiguration
 	@Configuration
 	protected static class RoutingFunctionConfiguration {