INT-3928 Ensure WS Adapters work when @EnableWS

JIRA: https://jira.spring.io/browse/INT-3928

The `@EnableWS` provides the `DelegatingWsConfiguration` which registers only `DefaultMethodEndpointAdapter`
overriding the default strategies including required for the SI `MessageEndpoint` implementations `MessageEndpointAdapter`.
That prevents the normal behavior for the SI gateways.

Implement `IntegrationConfigurationInitializer` for the WS module and register `MessageEndpointAdapter` bean for SI WS support.

spring-integration-ws/src/main/java/org/springframework/integration/ws/config/WsIntegrationConfigurationInitializer.java

@@ -0,0 +1,69 @@
+/*
+ * Copyright 2016 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.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.integration.ws.config;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+
+import org.springframework.beans.BeansException;
+import org.springframework.beans.factory.config.BeanDefinition;
+import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
+import org.springframework.beans.factory.support.BeanDefinitionBuilder;
+import org.springframework.beans.factory.support.BeanDefinitionRegistry;
+import org.springframework.integration.config.IntegrationConfigurationInitializer;
+import org.springframework.ws.server.EndpointAdapter;
+import org.springframework.ws.server.endpoint.adapter.MessageEndpointAdapter;
+
+/**
+ * The {@link IntegrationConfigurationInitializer} implementation for the WebService module.
+ * Registers {@link MessageEndpointAdapter} bean, because the usage of
+ * {@link org.springframework.ws.config.annotation.EnableWs} switches off the registration for the
+ * {@link MessageEndpointAdapter} as one of the default strategies.
+ * The {@link org.springframework.ws.config.annotation.EnableWs}
+ * registers only the {@link org.springframework.ws.server.endpoint.adapter.DefaultMethodEndpointAdapter},
+ * which isn't appropriate for the {@link org.springframework.ws.server.endpoint.MessageEndpoint} implementations.
+ *
+ *
+ * @author Artem Bilan
+ * @since 4.3
+ * @see org.springframework.ws.config.annotation.EnableWs
+ * @see org.springframework.ws.server.MessageDispatcher
+ */
+public class WsIntegrationConfigurationInitializer implements IntegrationConfigurationInitializer {
+
+	private static final String MESSAGE_ENDPOINT_ADAPTER_BEAN_NAME = "integrationWsMessageEndpointAdapter";
+
+	private static final Log logger = LogFactory.getLog(WsIntegrationConfigurationInitializer.class);
+
+	@Override
+	public void initialize(ConfigurableListableBeanFactory beanFactory) throws BeansException {
+		if (beanFactory instanceof BeanDefinitionRegistry) {
+			if (beanFactory.getBeanNamesForType(EndpointAdapter.class, false, false).length > 0) {
+				BeanDefinitionBuilder requestMappingBuilder =
+						BeanDefinitionBuilder.genericBeanDefinition(MessageEndpointAdapter.class);
+				requestMappingBuilder.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
+				((BeanDefinitionRegistry) beanFactory).registerBeanDefinition(MESSAGE_ENDPOINT_ADAPTER_BEAN_NAME,
+						requestMappingBuilder.getBeanDefinition());
+			}
+		}
+		else {
+			logger.warn("'IntegrationRequestMappingHandlerMapping' isn't registered because 'beanFactory'" +
+					" isn't an instance of `BeanDefinitionRegistry`.");
+		}
+	}
+
+}

spring-integration-ws/src/main/resources/META-INF/spring.factories

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+org.springframework.integration.config.IntegrationConfigurationInitializer=\
+org.springframework.integration.ws.config.WsIntegrationConfigurationInitializer