INT-4448, INT-4449: Fix Gateway for no-arg method (#2420)

* INT-4448, INT-4449: Fix Gateway for no-arg method

JIRA: https://jira.spring.io/browse/INT-4448
JIRA: https://jira.spring.io/browse/INT-4449

When we are not interested in the `payload` to send, we use a gateway
method without any args, but in this case for send operation (or
send-and-receive) we should specify a default `payloadExpression`

The `MessagingGatewayRegistrar` fails with `NPE` if we don't have a
any global headers and have `defaultPayloadExpression`

Also in this case the `GatewayProxyFactoryBean` fails to send
and fallbacks to receive with the meaning "no args, not payloadExpression"

* Fix `MessagingGatewayRegistrar` to check `hasDefaultHeaders` before
processing them
* Fix `GatewayProxyFactoryBean` to consult `this.globalMethodMetadata`
if there is no `payloadExpression` for the method specific metadata

**Cherry-pick to 5.0.x and 4.3.x**

* Remove `oracle-java8-installer` since it looks like the resource
is not available anymore:

```
Location: http://download.oracle.com/otn-pub/java/jdk/8u161-b12/2f38c3b165be4555a1fa6e98c45e0808/jdk-8u161-linux-x64.tar.gz?AuthParam=1523990114_ee8c82cbe67bc87d192cb79d3b902d2f [following]
--2018-04-17 18:33:14--  http://download.oracle.com/otn-pub/java/jdk/8u161-b12/2f38c3b165be4555a1fa6e98c45e0808/jdk-8u161-linux-x64.tar.gz?AuthParam=1523990114_ee8c82cbe67bc87d192cb79d3b902d2f
Connecting to download.oracle.com (download.oracle.com)|23.53.120.105|:80... connected.
HTTP request sent, awaiting response... 404 Not Found
2018-04-17 18:35:15 ERROR 404: Not Found.
```

spring-integration-core/src/main/java/org/springframework/integration/config/MessagingGatewayRegistrar.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2016 the original author or authors.
+ * Copyright 2014-2018 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.
@@ -114,29 +114,35 @@ public class MessagingGatewayRegistrar implements ImportBeanDefinitionRegistrar,
 						: GatewayProxyFactoryBean.class);
 
 		if (hasDefaultHeaders || hasDefaultPayloadExpression) {
-			BeanDefinitionBuilder methodMetadataBuilder = BeanDefinitionBuilder.genericBeanDefinition(GatewayMethodMetadata.class);
+			BeanDefinitionBuilder methodMetadataBuilder =
+					BeanDefinitionBuilder.genericBeanDefinition(GatewayMethodMetadata.class);
+
 			if (hasDefaultPayloadExpression) {
 				methodMetadataBuilder.addPropertyValue("payloadExpression", defaultPayloadExpression);
 			}
-			Map<String, Object> headerExpressions = new ManagedMap<String, Object>();
-			for (Map<String, Object> header : defaultHeaders) {
-				String headerValue = (String) header.get("value");
-				String headerExpression = (String) header.get("expression");
-				boolean hasValue = StringUtils.hasText(headerValue);
 
-				if (hasValue == StringUtils.hasText(headerExpression)) {
-					throw new BeanDefinitionStoreException("exactly one of 'value' or 'expression' " +
-							"is required on a gateway's header.");
+			if (hasDefaultHeaders) {
+				Map<String, Object> headerExpressions = new ManagedMap<String, Object>();
+				for (Map<String, Object> header : defaultHeaders) {
+					String headerValue = (String) header.get("value");
+					String headerExpression = (String) header.get("expression");
+					boolean hasValue = StringUtils.hasText(headerValue);
+
+					if (hasValue == StringUtils.hasText(headerExpression)) {
+						throw new BeanDefinitionStoreException("exactly one of 'value' or 'expression' " +
+								"is required on a gateway's header.");
+					}
+
+					BeanDefinition expressionDef =
+							new RootBeanDefinition(hasValue ? LiteralExpression.class : ExpressionFactoryBean.class);
+					expressionDef.getConstructorArgumentValues()
+							.addGenericArgumentValue(hasValue ? headerValue : headerExpression);
+
+					headerExpressions.put((String) header.get("name"), expressionDef);
 				}
-
-				BeanDefinition expressionDef =
-						new RootBeanDefinition(hasValue ? LiteralExpression.class : ExpressionFactoryBean.class);
-				expressionDef.getConstructorArgumentValues()
-						.addGenericArgumentValue(hasValue ? headerValue : headerExpression);
-
-				headerExpressions.put((String) header.get("name"), expressionDef);
+				methodMetadataBuilder.addPropertyValue("headerExpressions", headerExpressions);
 			}
-			methodMetadataBuilder.addPropertyValue("headerExpressions", headerExpressions);
+
 			gatewayProxyBuilder.addPropertyValue("globalMethodMetadata", methodMetadataBuilder.getBeanDefinition());
 		}
 

spring-integration-core/src/main/java/org/springframework/integration/gateway/GatewayProxyFactoryBean.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -454,10 +454,15 @@ public class GatewayProxyFactoryBean extends AbstractEndpoint
 		boolean hasPayloadExpression =
 				method.isAnnotationPresent(org.springframework.integration.annotation.Payload.class)
 						|| method.isAnnotationPresent(Payload.class);
-		if (!hasPayloadExpression && this.methodMetadataMap != null) {
+		if (!hasPayloadExpression) {
 			// check for the method metadata next
-			GatewayMethodMetadata metadata = this.methodMetadataMap.get(method.getName());
-			hasPayloadExpression = (metadata != null) && StringUtils.hasText(metadata.getPayloadExpression());
+			if (this.methodMetadataMap != null) {
+				GatewayMethodMetadata metadata = this.methodMetadataMap.get(method.getName());
+				hasPayloadExpression = (metadata != null) && StringUtils.hasText(metadata.getPayloadExpression());
+			}
+			else if (this.globalMethodMetadata != null) {
+				hasPayloadExpression = StringUtils.hasText(this.globalMethodMetadata.getPayloadExpression());
+			}
 		}
 		if (paramCount == 0 && !hasPayloadExpression) {
 			if (shouldReply) {

spring-integration-core/src/test/java/org/springframework/integration/gateway/GatewayInterfaceTests-context.xml

@@ -10,7 +10,7 @@
 	</int:channel>
 
 	<int:gateway id="sampleGateway"
-			service-interface="org.springframework.integration.gateway.GatewayInterfaceTests.Bar"
+			service-interface="org.springframework.integration.gateway.GatewayInterfaceTests$Bar"
 			default-request-channel="requestChannelBaz"
 			error-channel="errorChannel">
 		<int:default-header name="name" expression="#gatewayMethod.name"/>
@@ -35,9 +35,14 @@
 	<int:channel id="requestChannelBaz"/>
 
 	<int:gateway id="customMappedGateway"
-			service-interface="org.springframework.integration.gateway.GatewayInterfaceTests.Baz"
+			service-interface="org.springframework.integration.gateway.GatewayInterfaceTests$Baz"
 			default-request-channel="requestChannelBaz" mapper="mapper"/>
 
 	<bean id="mapper" class="org.springframework.integration.gateway.GatewayInterfaceTests$BazMapper"/>
 
+	<int:gateway id="sampleGateway2"
+				 service-interface="org.springframework.integration.gateway.GatewayInterfaceTests$NoArgumentsGateway"
+				 default-request-channel="requestChannelBar"
+				 default-payload-expression="'foo'"/>
+
 </beans>

spring-integration-core/src/test/java/org/springframework/integration/gateway/GatewayInterfaceTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -68,6 +68,7 @@ import org.springframework.integration.config.EnableIntegration;
 import org.springframework.integration.configuration.EnableIntegrationTests.TestMessagingGateway;
 import org.springframework.integration.context.IntegrationContextUtils;
 import org.springframework.integration.context.IntegrationProperties;
+import org.springframework.integration.handler.AbstractReplyProducingMessageHandler;
 import org.springframework.integration.handler.BridgeHandler;
 import org.springframework.integration.support.MessageBuilder;
 import org.springframework.integration.test.util.TestUtils;
@@ -441,6 +442,26 @@ public class GatewayInterfaceTests {
 		((SubscribableChannel) this.errorChannel).unsubscribe(messageHandler);
 	}
 
+	@Test
+	public void testGatewayWithNoArgsMethod() {
+		ConfigurableApplicationContext ac =
+				new ClassPathXmlApplicationContext("GatewayInterfaceTests-context.xml", getClass());
+
+		DirectChannel channel = ac.getBean("requestChannelBar", DirectChannel.class);
+		channel.subscribe(new AbstractReplyProducingMessageHandler() {
+
+			@Override
+			protected Object handleRequestMessage(Message<?> requestMessage) {
+				assertEquals("foo", requestMessage.getPayload());
+				return "FOO";
+			}
+
+		});
+
+		NoArgumentsGateway noArgumentsGateway = ac.getBean(NoArgumentsGateway.class);
+		assertEquals("FOO", noArgumentsGateway.pullData());
+		ac.close();
+	}
 
 	public interface Foo {
 
@@ -469,6 +490,11 @@ public class GatewayInterfaceTests {
 		void baz(String payload);
 	}
 
+	public interface NoArgumentsGateway {
+
+		String pullData();
+	}
+
 	public static class BazMapper implements MethodArgsMessageMapper {
 
 		@Override