INT-3991: Add IntegrationGraphController

JIRA: https://jira.spring.io/browse/INT-3991

* Add `IntegrationGraphController` `@RestController` over `IntegrationGraphServer` bean
* Add `@EnableIntegrationGraphController` and `<int-http:graph-controller>` to register
`IntegrationGraphController` if the `DispatcherServlet` is in classpath.
* Also register the `IntegrationGraphServer` bean from the same place, if that isn't presented in the application context yet.
* Allow to configure the "root" `path` for the `IntegrationGraphController` as a placeholder value via
`spring.integration.graph.controller.request.mapping.path` property
* Add tests for both `@EnableIntegrationGraphController` and `<int-http:graph-controller>` cases based on the `MockMvc`

spring-integration-http/src/main/java/org/springframework/integration/http/config/EnableIntegrationGraphController.java

@@ -0,0 +1,61 @@
+/*
+ * 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.http.config;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Inherited;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+import org.springframework.context.annotation.Import;
+import org.springframework.core.annotation.AliasFor;
+import org.springframework.integration.http.management.IntegrationGraphController;
+import org.springframework.integration.http.support.HttpContextUtils;
+
+/**
+ * Enables the {@link IntegrationGraphController} if {@code DispatcherServlet} is present in the classpath.
+ *
+ * @author Artem Bilan
+ *
+ * @since 4.3
+ *
+ * @see  IntegrationGraphController
+ */
+@Target(ElementType.TYPE)
+@Retention(RetentionPolicy.RUNTIME)
+@Inherited
+@Import(IntegrationGraphControllerRegistrarImportSelector.class)
+public @interface EnableIntegrationGraphController {
+
+	/**
+	 * Specify the Request Mapping path for the {@link IntegrationGraphController}.
+	 * Defaults to {@value HttpContextUtils#GRAPH_CONTROLLER_DEFAULT_PATH}.
+	 * @return The Request Mapping path for the {@link IntegrationGraphController}
+	 */
+	@AliasFor("path")
+	String value() default HttpContextUtils.GRAPH_CONTROLLER_DEFAULT_PATH;
+
+	/**
+	 * Specify the Request Mapping path for the {@link IntegrationGraphController}.
+	 * Defaults to {@value HttpContextUtils#GRAPH_CONTROLLER_DEFAULT_PATH}.
+	 * @return The Request Mapping path for the {@link IntegrationGraphController}
+	 */
+	@AliasFor("value")
+	String path() default HttpContextUtils.GRAPH_CONTROLLER_DEFAULT_PATH;
+
+}

spring-integration-http/src/main/java/org/springframework/integration/http/config/HttpIntegrationConfigurationInitializer.java

@@ -28,7 +28,6 @@ import org.springframework.integration.config.IntegrationConfigurationInitialize
 import org.springframework.integration.config.xml.IntegrationNamespaceUtils;
 import org.springframework.integration.http.inbound.IntegrationRequestMappingHandlerMapping;
 import org.springframework.integration.http.support.HttpContextUtils;
-import org.springframework.util.ClassUtils;
 
 /**
  * The HTTP Integration infrastructure {@code beanFactory} initializer.
@@ -40,9 +39,6 @@ public class HttpIntegrationConfigurationInitializer implements IntegrationConfi
 
 	private static final Log logger = LogFactory.getLog(HttpIntegrationConfigurationInitializer.class);
 
-	private static final boolean servletPresent = ClassUtils.isPresent("javax.servlet.Servlet",
-			HttpIntegrationConfigurationInitializer.class.getClassLoader());
-
 	@Override
 	public void initialize(ConfigurableListableBeanFactory beanFactory) throws BeansException {
 		if (beanFactory instanceof BeanDefinitionRegistry) {
@@ -65,7 +61,8 @@ public class HttpIntegrationConfigurationInitializer implements IntegrationConfi
 	 * the HTTP server components.
 	 */
 	private void registerRequestMappingHandlerMappingIfNecessary(BeanDefinitionRegistry registry) {
-		if (servletPresent && !registry.containsBeanDefinition(HttpContextUtils.HANDLER_MAPPING_BEAN_NAME)) {
+		if (HttpContextUtils.SERVLET_PRESENT &&
+				!registry.containsBeanDefinition(HttpContextUtils.HANDLER_MAPPING_BEAN_NAME)) {
 			BeanDefinitionBuilder requestMappingBuilder =
 					BeanDefinitionBuilder.genericBeanDefinition(IntegrationRequestMappingHandlerMapping.class);
 			requestMappingBuilder.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);

spring-integration-http/src/main/java/org/springframework/integration/http/config/HttpNamespaceHandler.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2010 the original author or authors.
+ * Copyright 2002-2016 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.
@@ -22,15 +22,18 @@ import org.springframework.integration.config.xml.AbstractIntegrationNamespaceHa
  * Namespace handler for Spring Integration's <em>http</em> namespace.
  *
  * @author Mark Fisher
+ * @author Artem Bilan
+ *
  * @since 1.0.2
  */
 public class HttpNamespaceHandler extends AbstractIntegrationNamespaceHandler {
 
 	public void init() {
-		this.registerBeanDefinitionParser("inbound-channel-adapter", new HttpInboundEndpointParser(false));
-		this.registerBeanDefinitionParser("inbound-gateway", new HttpInboundEndpointParser(true));
-		this.registerBeanDefinitionParser("outbound-channel-adapter", new HttpOutboundChannelAdapterParser());
-		this.registerBeanDefinitionParser("outbound-gateway", new HttpOutboundGatewayParser());
+		registerBeanDefinitionParser("inbound-channel-adapter", new HttpInboundEndpointParser(false));
+		registerBeanDefinitionParser("inbound-gateway", new HttpInboundEndpointParser(true));
+		registerBeanDefinitionParser("outbound-channel-adapter", new HttpOutboundChannelAdapterParser());
+		registerBeanDefinitionParser("outbound-gateway", new HttpOutboundGatewayParser());
+		registerBeanDefinitionParser("graph-controller", new IntegrationGraphControllerParser());
 	}
 
 }

spring-integration-http/src/main/java/org/springframework/integration/http/config/IntegrationGraphControllerParser.java

@@ -0,0 +1,63 @@
+/*
+ * 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.http.config;
+
+import java.util.Collections;
+import java.util.Map;
+
+import org.w3c.dom.Element;
+
+import org.springframework.beans.factory.config.BeanDefinition;
+import org.springframework.beans.factory.xml.BeanDefinitionParser;
+import org.springframework.beans.factory.xml.ParserContext;
+import org.springframework.core.type.StandardAnnotationMetadata;
+import org.springframework.integration.http.support.HttpContextUtils;
+
+/**
+ * The {@link BeanDefinitionParser} for the {@code <int-http:graph-controller>} component.
+ * @author Artem Bilan
+ *
+ * @since 4.3
+ */
+public class IntegrationGraphControllerParser implements BeanDefinitionParser {
+
+	private final IntegrationGraphControllerRegistrar graphControllerRegistrar =
+			new IntegrationGraphControllerRegistrar();
+
+	@Override
+	public BeanDefinition parse(final Element element, ParserContext parserContext) {
+		if (HttpContextUtils.SERVLET_PRESENT) {
+			this.graphControllerRegistrar.registerBeanDefinitions(
+					new StandardAnnotationMetadata(IntegrationGraphControllerParser.class) {
+
+						@Override
+						public Map<String, Object> getAnnotationAttributes(String annotationType) {
+							return Collections.<String, Object>singletonMap("value", element.getAttribute("path"));
+						}
+
+					}, parserContext.getRegistry());
+		}
+		else {
+			parserContext.getReaderContext().warning("The 'IntegrationGraphController' isn't registered " +
+					"with the application context because" +
+					" there is no 'org.springframework.web.servlet.DispatcherServlet' in the classpath.", element);
+		}
+
+		return null;
+	}
+
+}

spring-integration-http/src/main/java/org/springframework/integration/http/config/IntegrationGraphControllerRegistrar.java

@@ -0,0 +1,101 @@
+/*
+ * 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.http.config;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import org.springframework.beans.BeansException;
+import org.springframework.beans.factory.config.BeanDefinition;
+import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
+import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
+import org.springframework.beans.factory.support.AbstractBeanDefinition;
+import org.springframework.beans.factory.support.BeanDefinitionBuilder;
+import org.springframework.beans.factory.support.BeanDefinitionReaderUtils;
+import org.springframework.beans.factory.support.BeanDefinitionRegistry;
+import org.springframework.beans.factory.support.RootBeanDefinition;
+import org.springframework.context.EnvironmentAware;
+import org.springframework.context.annotation.ImportBeanDefinitionRegistrar;
+import org.springframework.core.annotation.AnnotationUtils;
+import org.springframework.core.env.ConfigurableEnvironment;
+import org.springframework.core.env.Environment;
+import org.springframework.core.env.MapPropertySource;
+import org.springframework.core.type.AnnotationMetadata;
+import org.springframework.integration.context.IntegrationContextUtils;
+import org.springframework.integration.http.management.IntegrationGraphController;
+import org.springframework.integration.http.support.HttpContextUtils;
+import org.springframework.integration.support.management.graph.IntegrationGraphServer;
+
+/**
+ * @author Artem Bilan
+ * @since 4.3
+ */
+class IntegrationGraphControllerRegistrar implements ImportBeanDefinitionRegistrar {
+
+	@Override
+	public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
+		Map<String, Object> annotationAttributes =
+				importingClassMetadata.getAnnotationAttributes(EnableIntegrationGraphController.class.getName());
+
+		if (!registry.containsBeanDefinition(IntegrationContextUtils.INTEGRATION_GRAPH_SERVER_BEAN_NAME)) {
+			registry.registerBeanDefinition(IntegrationContextUtils.INTEGRATION_GRAPH_SERVER_BEAN_NAME,
+					new RootBeanDefinition(IntegrationGraphServer.class));
+		}
+
+		if (!registry.containsBeanDefinition(HttpContextUtils.GRAPH_CONTROLLER_BEAN_NAME)) {
+			AbstractBeanDefinition controllerPropertiesPopulator =
+					BeanDefinitionBuilder.genericBeanDefinition(GraphControllerPropertiesPopulator.class)
+							.addConstructorArgValue(annotationAttributes)
+							.setRole(BeanDefinition.ROLE_INFRASTRUCTURE)
+							.getBeanDefinition();
+			BeanDefinitionReaderUtils.registerWithGeneratedName(controllerPropertiesPopulator, registry);
+
+			BeanDefinition graphController =
+					BeanDefinitionBuilder.genericBeanDefinition(IntegrationGraphController.class)
+							.addConstructorArgReference(IntegrationContextUtils.INTEGRATION_GRAPH_SERVER_BEAN_NAME)
+							.getBeanDefinition();
+
+			registry.registerBeanDefinition(HttpContextUtils.GRAPH_CONTROLLER_BEAN_NAME, graphController);
+		}
+	}
+
+	private static final class GraphControllerPropertiesPopulator
+			implements BeanFactoryPostProcessor, EnvironmentAware {
+
+		private final Map<String, Object> properties = new HashMap<String, Object>();
+
+		private GraphControllerPropertiesPopulator(Map<String, Object> annotationAttributes) {
+			Object graphControllerPath = annotationAttributes.get(AnnotationUtils.VALUE);
+			this.properties.put(HttpContextUtils.GRAPH_CONTROLLER_PATH_PROPERTY, graphControllerPath);
+		}
+
+		@Override
+		public void setEnvironment(Environment environment) {
+			((ConfigurableEnvironment) environment)
+					.getPropertySources()
+					.addLast(new MapPropertySource(HttpContextUtils.GRAPH_CONTROLLER_BEAN_NAME + "_properties",
+							this.properties));
+		}
+
+		@Override
+		public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
+
+		}
+
+	}
+
+}

spring-integration-http/src/main/java/org/springframework/integration/http/config/IntegrationGraphControllerRegistrarImportSelector.java

@@ -0,0 +1,47 @@
+/*
+ * 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.http.config;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+
+import org.springframework.context.annotation.ImportSelector;
+import org.springframework.core.type.AnnotationMetadata;
+import org.springframework.integration.http.support.DefaultHttpHeaderMapper;
+import org.springframework.integration.http.support.HttpContextUtils;
+
+/**
+ * @author Artem Bilan
+ * @since 4.3
+ */
+class IntegrationGraphControllerRegistrarImportSelector implements ImportSelector {
+
+	private static final Log logger = LogFactory.getLog(DefaultHttpHeaderMapper.class);
+
+	@Override
+	public String[] selectImports(AnnotationMetadata importingClassMetadata) {
+		if (HttpContextUtils.SERVLET_PRESENT) {
+			return new String[] { IntegrationGraphControllerRegistrar.class.getName() };
+		}
+		else {
+			logger.warn("The 'IntegrationGraphController' isn't registered with the application context because" +
+					" there is no 'org.springframework.web.servlet.DispatcherServlet' in the classpath.");
+			return new String[0];
+		}
+	}
+
+}

spring-integration-http/src/main/java/org/springframework/integration/http/management/IntegrationGraphController.java

@@ -0,0 +1,57 @@
+/*
+ * 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.http.management;
+
+import org.springframework.integration.http.support.HttpContextUtils;
+import org.springframework.integration.support.management.graph.Graph;
+import org.springframework.integration.support.management.graph.IntegrationGraphServer;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+/**
+ * The REST Controller to provide the management API over {@link IntegrationGraphServer}.
+ *
+ * @author Artem Bilan
+ *
+ * @since 4.3
+ */
+@RestController
+@RequestMapping(IntegrationGraphController.REQUEST_MAPPING_PATH_VARIABLE)
+public class IntegrationGraphController {
+
+	final static String REQUEST_MAPPING_PATH_VARIABLE =
+			"${" + HttpContextUtils.GRAPH_CONTROLLER_PATH_PROPERTY +  ":" +
+					HttpContextUtils.GRAPH_CONTROLLER_DEFAULT_PATH + "}";
+
+	private final IntegrationGraphServer integrationGraphServer;
+
+	public IntegrationGraphController(IntegrationGraphServer integrationGraphServer) {
+		this.integrationGraphServer = integrationGraphServer;
+	}
+
+	@GetMapping(name = "getGraph")
+	public Graph getGraph() {
+		return this.integrationGraphServer.getGraph();
+	}
+
+	@GetMapping(path = "/refresh", name = "refreshGraph")
+	public Graph refreshGraph() {
+		return this.integrationGraphServer.rebuild();
+	}
+
+}

spring-integration-http/src/main/java/org/springframework/integration/http/management/package-info.java

@@ -0,0 +1,4 @@
+/**
+ * Provides classes related to management support.
+ */
+package org.springframework.integration.http.management;

spring-integration-http/src/main/java/org/springframework/integration/http/support/HttpContextUtils.java

@@ -16,8 +16,11 @@
 
 package org.springframework.integration.http.support;
 
+import org.springframework.util.ClassUtils;
+
 /**
- * Utility class for accessing HTTP integration components from the {@link org.springframework.beans.factory.BeanFactory}.
+ * Utility class for accessing HTTP integration components
+ * from the {@link org.springframework.beans.factory.BeanFactory}.
  *
  * @author Artem Bilan
  * @author Gary Russell
@@ -29,9 +32,34 @@ public final class HttpContextUtils {
 		super();
 	}
 
+	/**
+	 * The {@code boolean} flag to indicate if the {@code org.springframework.web.servlet.DispatcherServlet}
+	 * is present in the CLASSPATH to allow to register the Integration server components,
+	 * e.g. {@code IntegrationGraphController}.
+	 */
+	public static final boolean SERVLET_PRESENT =
+			ClassUtils.isPresent("org.springframework.web.servlet.DispatcherServlet",
+			HttpContextUtils.class.getClassLoader());
+
 	/**
 	 * @see org.springframework.integration.http.config.HttpInboundEndpointParser
 	 */
 	public static final String HANDLER_MAPPING_BEAN_NAME = "integrationRequestMappingHandlerMapping";
 
+	/**
+	 * Represents the environment property for the {@code IntegrationGraphController} request mapping path.
+	 */
+	public static final String GRAPH_CONTROLLER_PATH_PROPERTY =
+			"spring.integration.graph.controller.request.mapping.path";
+
+	/**
+	 * Represents the default request mapping path for the {@code IntegrationGraphController}.
+	 */
+	public static final String GRAPH_CONTROLLER_DEFAULT_PATH = "/integration";
+
+	/**
+	 * Represents the bean name for the default {@code IntegrationGraphController}.
+	 */
+	public static final String GRAPH_CONTROLLER_BEAN_NAME = "integrationGraphController";
+
 }

spring-integration-http/src/main/resources/org/springframework/integration/http/config/spring-integration-http-4.3.xsd

@@ -492,6 +492,28 @@
 		</xsd:complexType>
 	</xsd:element>
 
+	<xsd:element name="graph-controller">
+		<xsd:annotation>
+			<xsd:documentation>
+				Configures a
+				'org.springframework.integration.http.management.IntegrationGraphController' bean
+				to expose a REST API for the
+				'org.springframework.integration.support.management.graph.IntegrationGraphServer' bean.
+				Note: Spring Web MVC must be present in the application to enable and register this component.
+			</xsd:documentation>
+		</xsd:annotation>
+		<xsd:complexType>
+			<xsd:attribute name="path" type="xsd:string" default="/integration">
+				<xsd:annotation>
+					<xsd:documentation>
+						The root request mapping path for the 'IntegrationGraphController'.
+						Defaults to /integration.
+					</xsd:documentation>
+				</xsd:annotation>
+			</xsd:attribute>
+		</xsd:complexType>
+	</xsd:element>
+
 	<xsd:complexType name="uriVariableType">
 		<xsd:annotation>
 			<xsd:documentation><![CDATA[