GH-891 Ensure HTTP Request params are mapped even when body is not present

Resolves #891

spring-cloud-function-web/src/test/java/org/springframework/cloud/function/web/function/FunctionEndpointInitializerTests.java

@@ -18,23 +18,34 @@ package org.springframework.cloud.function.web.function;
 
 import java.net.URI;
 import java.time.Duration;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.function.BiFunction;
 import java.util.function.Consumer;
 import java.util.function.Function;
 import java.util.function.Supplier;
 
 import org.junit.jupiter.api.Test;
 
+import org.springframework.boot.SpringApplication;
 import org.springframework.boot.SpringBootConfiguration;
+import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
 import org.springframework.boot.test.web.client.TestRestTemplate;
 import org.springframework.cloud.function.context.FunctionRegistration;
 import org.springframework.cloud.function.context.FunctionalSpringApplication;
 import org.springframework.cloud.function.context.catalog.FunctionTypeUtils;
 import org.springframework.context.ApplicationContextInitializer;
 import org.springframework.context.ConfigurableApplicationContext;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
 import org.springframework.context.support.GenericApplicationContext;
 import org.springframework.core.ResolvableType;
+import org.springframework.http.HttpEntity;
+import org.springframework.http.HttpHeaders;
+import org.springframework.http.HttpMethod;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseEntity;
+import org.springframework.web.util.UriComponentsBuilder;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.awaitility.Awaitility.await;
@@ -47,6 +58,28 @@ import static org.awaitility.Awaitility.await;
 */
 public class FunctionEndpointInitializerTests {
 
+	@SuppressWarnings({ "rawtypes", "unchecked" })
+	@Test
+	public void testEmptyBodyRequestParameters() throws Exception {
+		int port = startServerAndWaitForPort(BeansConfiguration.class, false);
+		TestRestTemplate testRestTemplate = new TestRestTemplate();
+		Map<String, String> params = new HashMap<>();
+		params.put("fname", "Jim");
+		params.put("lname", "Lahey");
+
+		HttpHeaders headers = new HttpHeaders();
+		headers.set("Accept", "application/json");
+		HttpEntity entity = new HttpEntity(headers);
+
+		String urlTemplate = UriComponentsBuilder.fromHttpUrl("http://localhost:" + port + "/nullPayload")
+				.queryParam("fname", "Jim").queryParam("lname", "Lahey").encode().toUriString();
+
+		ResponseEntity<String> response = testRestTemplate.exchange(urlTemplate, HttpMethod.GET, entity, String.class);
+		String res = response.getBody();
+		assertThat(res).contains("Jim");
+		assertThat(res).contains("Lahey");
+	}
+
 	@Test
 	public void testNonExistingFunction() throws Exception {
 		int port = startServerAndWaitForPort(ApplicationConfiguration.class);
@@ -105,8 +138,10 @@ public class FunctionEndpointInitializerTests {
 		assertThat(response.getBody()).isEqualTo("Jim Lahey");
 	}
 
-	private int startServerAndWaitForPort(Class<?> primaryAppConfig) throws InterruptedException {
-		ConfigurableApplicationContext context = FunctionalSpringApplication.run(primaryAppConfig, "--server.port=0");
+	private int startServerAndWaitForPort(Class<?> primaryAppConfig, boolean functional) throws InterruptedException {
+		ConfigurableApplicationContext context = functional
+				? FunctionalSpringApplication.run(primaryAppConfig, "--server.port=0")
+						: SpringApplication.run(primaryAppConfig, "--server.port=0");
 		await()
 			.pollDelay(Duration.ofMillis(500))
 			.pollInterval(Duration.ofMillis(500))
@@ -118,6 +153,10 @@ public class FunctionEndpointInitializerTests {
 		return Integer.valueOf(context.getEnvironment().getProperty("local.server.port"));
 	}
 
+	private int startServerAndWaitForPort(Class<?> primaryAppConfig) throws InterruptedException {
+		return this.startServerAndWaitForPort(primaryAppConfig, true);
+	}
+
 	@SpringBootConfiguration
 	protected static class ConsumerConfiguration
 			implements ApplicationContextInitializer<GenericApplicationContext> {
@@ -136,6 +175,17 @@ public class FunctionEndpointInitializerTests {
 
 	}
 
+	@EnableAutoConfiguration
+	@Configuration
+	protected static class BeansConfiguration {
+		@Bean
+		public BiFunction<String, Map<String, Object>, Map<String, Object>> nullPayload() {
+			return (p, h) -> {
+				return h;
+			};
+		}
+	}
+
 
 	@SpringBootConfiguration
 	protected static class ApplicationConfiguration