INT-4042: Support Known Router Channels in Graph

JIRA: https://jira.spring.io/browse/INT-4042

```
...
  }, {
    "nodeId" : 24,
    "name" : "integrationGraphServerTests.Config.router.router",
    "stats" : {
       ...
      }
    },
    "componentType" : "router",
    "output" : "discards",
    "input" : "four",
    "routes" : [ "barChannel", "bazChannel" ],
    "errors" : "myErrors"
  }, {
...
    "from" : 3,
    "to" : 24,
    "type" : "input"
  }, {
    "from" : 24,
    "to" : 7,
    "type" : "output"
  }, {
    "from" : 24,
    "to" : 2,
    "type" : "error"
  }, {
    "from" : 24,
    "to" : 5,
    "type" : "route"
  }, {
    "from" : 24,
    "to" : 6,
    "type" : "route"
...
```

Add Graph Support for RecipientListRouter

The RLR is not an AMMR; it's the only router outside of that class hierarchy.

Polishing

Add Dynamically Routed-to Channels to Graph

Add ExpressionBased and Expose Expression in Graph

Polishing

Add getExpressionString() to IOS

Add ExpressionCapable; Set Primary Expression

Polishing - PR Comments

Router/Expression Docs

* Simple Java Docs polishing

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

@@ -98,7 +98,9 @@ public class ServiceActivatorFactoryBean extends AbstractStandardMessageHandlerF
 	protected MessageHandler createExpressionEvaluatingHandler(Expression expression) {
 		ExpressionEvaluatingMessageProcessor<Object> processor = new ExpressionEvaluatingMessageProcessor<Object>(expression);
 		processor.setBeanFactory(this.getBeanFactory());
-		return this.configureHandler(new ServiceActivatingHandler(processor));
+		ServiceActivatingHandler handler = new ServiceActivatingHandler(processor);
+		handler.setPrimaryExpression(expression);
+		return this.configureHandler(handler);
 	}
 
 	@Override

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

@@ -63,7 +63,9 @@ public class TransformerFactoryBean extends AbstractStandardMessageHandlerFactor
 	@Override
 	protected MessageHandler createExpressionEvaluatingHandler(Expression expression) {
 		Transformer transformer = new ExpressionEvaluatingTransformer(expression);
-		return this.createHandler(transformer);
+		MessageTransformingHandler handler = this.createHandler(transformer);
+		handler.setPrimaryExpression(expression);
+		return handler;
 	}
 
 	protected MessageTransformingHandler createHandler(Transformer transformer) {

spring-integration-core/src/main/java/org/springframework/integration/context/ExpressionCapable.java

@@ -0,0 +1,37 @@
+/*
+ * 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.context;
+
+import org.springframework.expression.Expression;
+
+/**
+ * Components that implement this interface are capable of supporting a primary
+ * SpEL expression as part of their configuration.
+ *
+ * @author Gary Russell
+ * @since 4.3
+ *
+ */
+public interface ExpressionCapable {
+
+	/**
+	 * Return the primary SpEL expression if this component is expression-based.
+	 * @return the expression as a String.
+	 */
+	Expression getExpression();
+
+}

spring-integration-core/src/main/java/org/springframework/integration/context/IntegrationObjectSupport.java

@@ -33,6 +33,7 @@ import org.springframework.context.ApplicationContext;
 import org.springframework.context.ApplicationContextAware;
 import org.springframework.core.convert.ConversionService;
 import org.springframework.core.convert.support.DefaultConversionService;
+import org.springframework.expression.Expression;
 import org.springframework.expression.ExpressionParser;
 import org.springframework.expression.spel.standard.SpelExpressionParser;
 import org.springframework.integration.support.DefaultMessageBuilderFactory;
@@ -63,7 +64,7 @@ import org.springframework.util.StringUtils;
  * @author Artem Bilan
  */
 public abstract class IntegrationObjectSupport implements BeanNameAware, NamedComponent,
-		ApplicationContextAware, BeanFactoryAware, InitializingBean {
+		ApplicationContextAware, BeanFactoryAware, InitializingBean, ExpressionCapable {
 
 	protected static final ExpressionParser EXPRESSION_PARSER = new SpelExpressionParser();
 
@@ -92,6 +93,8 @@ public abstract class IntegrationObjectSupport implements BeanNameAware, NamedCo
 
 	private volatile MessageBuilderFactory messageBuilderFactory;
 
+	private Expression expression;
+
 	@Override
 	public final void setBeanName(String beanName) {
 		this.beanName = beanName;
@@ -144,6 +147,20 @@ public abstract class IntegrationObjectSupport implements BeanNameAware, NamedCo
 		this.channelResolver = channelResolver;
 	}
 
+	@Override
+	public Expression getExpression() {
+		return this.expression;
+	}
+
+	/**
+	 * For expression-based components, set the primary expression.
+	 * @param expression the expression.
+	 * @since 4.3
+	 */
+	public final void setPrimaryExpression(Expression expression) {
+		this.expression = expression;
+	}
+
 	@Override
 	public final void afterPropertiesSet() {
 		this.integrationProperties = IntegrationContextUtils.getIntegrationProperties(this.beanFactory);

spring-integration-core/src/main/java/org/springframework/integration/endpoint/EventDrivenConsumer.java

@@ -19,6 +19,7 @@ package org.springframework.integration.endpoint;
 import org.springframework.context.Lifecycle;
 import org.springframework.integration.context.IntegrationObjectSupport;
 import org.springframework.integration.core.MessageProducer;
+import org.springframework.integration.router.MessageRouter;
 import org.springframework.integration.support.context.NamedComponent;
 import org.springframework.messaging.MessageChannel;
 import org.springframework.messaging.MessageHandler;
@@ -58,6 +59,9 @@ public class EventDrivenConsumer extends AbstractEndpoint implements Integration
 		if (this.handler instanceof MessageProducer) {
 			return ((MessageProducer) this.handler).getOutputChannel();
 		}
+		else if (this.handler instanceof MessageRouter) {
+			return ((MessageRouter) this.handler).getDefaultOutputChannel();
+		}
 		else {
 			return null;
 		}

spring-integration-core/src/main/java/org/springframework/integration/endpoint/ExpressionEvaluatingMessageSource.java

@@ -17,6 +17,7 @@
 package org.springframework.integration.endpoint;
 
 import org.springframework.expression.Expression;
+import org.springframework.integration.context.ExpressionCapable;
 import org.springframework.util.Assert;
 
 /**
@@ -24,7 +25,7 @@ import org.springframework.util.Assert;
  * @author Gary Russell
  * @since 2.0
  */
-public class ExpressionEvaluatingMessageSource<T> extends AbstractMessageSource<T> {
+public class ExpressionEvaluatingMessageSource<T> extends AbstractMessageSource<T> implements ExpressionCapable {
 
 	private final Expression expression;
 
@@ -47,4 +48,9 @@ public class ExpressionEvaluatingMessageSource<T> extends AbstractMessageSource<
 		return this.evaluateExpression(this.expression, this.expectedType);
 	}
 
+	@Override
+	public Expression getExpression() {
+		return this.expression;
+	}
+
 }

spring-integration-core/src/main/java/org/springframework/integration/endpoint/PollingConsumer.java

@@ -24,6 +24,7 @@ import java.util.List;
 import org.springframework.context.Lifecycle;
 import org.springframework.integration.channel.ExecutorChannelInterceptorAware;
 import org.springframework.integration.core.MessageProducer;
+import org.springframework.integration.router.MessageRouter;
 import org.springframework.integration.transaction.IntegrationResourceHolder;
 import org.springframework.messaging.Message;
 import org.springframework.messaging.MessageChannel;
@@ -83,6 +84,9 @@ public class PollingConsumer extends AbstractPollingEndpoint implements Integrat
 		if (this.handler instanceof MessageProducer) {
 			return ((MessageProducer) this.handler).getOutputChannel();
 		}
+		else if (this.handler instanceof MessageRouter) {
+			return ((MessageRouter) this.handler).getDefaultOutputChannel();
+		}
 		else {
 			return null;
 		}

spring-integration-core/src/main/java/org/springframework/integration/endpoint/SourcePollingChannelAdapter.java

@@ -26,6 +26,7 @@ import org.springframework.aop.support.AopUtils;
 import org.springframework.aop.support.NameMatchMethodPointcutAdvisor;
 import org.springframework.context.Lifecycle;
 import org.springframework.integration.aop.AbstractMessageSourceAdvice;
+import org.springframework.integration.context.ExpressionCapable;
 import org.springframework.integration.core.MessageSource;
 import org.springframework.integration.core.MessagingTemplate;
 import org.springframework.integration.history.MessageHistory;
@@ -66,6 +67,9 @@ public class SourcePollingChannelAdapter extends AbstractPollingEndpoint
 	 */
 	public void setSource(MessageSource<?> source) {
 		this.source = source;
+		if (source instanceof ExpressionCapable) {
+			setPrimaryExpression(((ExpressionCapable) source).getExpression());
+		}
 	}
 
 	/**

spring-integration-core/src/main/java/org/springframework/integration/handler/ExpressionEvaluatingMessageHandler.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2011 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.
@@ -25,6 +25,7 @@ import org.springframework.util.Assert;
  * the provided {@link Expression} expecting a <b>void return</b>.
  *
  * @author Artem Bilan
+ * @author Gary Russell
  * @see MethodInvokingMessageHandler
  * @since 2.1
  */
@@ -36,9 +37,9 @@ public class ExpressionEvaluatingMessageHandler extends AbstractMessageHandler {
 
 
 	public ExpressionEvaluatingMessageHandler(Expression expression) {
-		Assert.notNull(expression, "Expression must not be null");
-		this.processor = new ExpressionEvaluatingMessageProcessor<Void>(
-				expression, Void.class);
+		Assert.notNull(expression, "'expression' must not be null");
+		this.processor = new ExpressionEvaluatingMessageProcessor<Void>(expression, Void.class);
+		setPrimaryExpression(expression);
 	}
 
 

spring-integration-core/src/main/java/org/springframework/integration/router/AbstractMappingMessageRouter.java

@@ -19,9 +19,12 @@ package org.springframework.integration.router;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.HashMap;
+import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Map.Entry;
 import java.util.Properties;
 import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
@@ -50,6 +53,21 @@ import org.springframework.util.StringUtils;
  */
 public abstract class AbstractMappingMessageRouter extends AbstractMessageRouter implements MappingMessageRouterManagement {
 
+	private static final int DEFAULT_DYNAMIC_CHANNEL_LIMIT = 100;
+
+	private int dynamicChannelLimit = DEFAULT_DYNAMIC_CHANNEL_LIMIT;
+
+	@SuppressWarnings("serial")
+	private final Map<String, MessageChannel> dynamicChannels = Collections.<String, MessageChannel>synchronizedMap(
+			new LinkedHashMap<String, MessageChannel>(DEFAULT_DYNAMIC_CHANNEL_LIMIT, 0.75f, true) {
+
+				@Override
+				protected boolean removeEldestEntry(Entry<String, MessageChannel> eldest) {
+					return this.size() > AbstractMappingMessageRouter.this.dynamicChannelLimit;
+				}
+
+			});
+
 	protected volatile Map<String, String> channelMappings = new ConcurrentHashMap<String, String>();
 
 	private volatile String prefix;
@@ -97,6 +115,18 @@ public abstract class AbstractMappingMessageRouter extends AbstractMessageRouter
 		this.resolutionRequired = resolutionRequired;
 	}
 
+	/**
+	 * Set a limit for how many dynamic channels are retained (for reporting purposes).
+	 * When the limit is exceeded, the oldest channel is discarded.
+	 * <p><b>NOTE: this does not affect routing, just the reporting which dynamically
+	 * resolved channels have been routed to.</b> Default {@code 100}.
+	 * @param dynamicChannelLimit the limit.
+	 * @see #getDynamicChannelNames()
+	 */
+	public void setDynamicChannelLimit(int dynamicChannelLimit) {
+		this.dynamicChannelLimit = dynamicChannelLimit;
+	}
+
 	/**
 	 * Returns an unmodifiable version of the channel mappings.
 	 * This is intended for use by subclasses only.
@@ -133,6 +163,12 @@ public abstract class AbstractMappingMessageRouter extends AbstractMessageRouter
 		this.channelMappings = newChannelMappings;
 	}
 
+	@Override
+	@ManagedAttribute
+	public Collection<String> getDynamicChannelNames() {
+		return Collections.unmodifiableSet(this.dynamicChannels.keySet());
+	}
+
 	/**
 	 * Subclasses must implement this method to return the channel keys.
 	 * A "key" might be present in this router's "channelMappings", or it
@@ -208,8 +244,10 @@ public abstract class AbstractMappingMessageRouter extends AbstractMessageRouter
 		// if the channelMappings contains a mapping, we'll use the mapped value
 		// otherwise, the String-based channelKey itself will be used as the channel name
 		String channelName = channelKey;
+		boolean mapped = false;
 		if (this.channelMappings.containsKey(channelKey)) {
 			channelName = this.channelMappings.get(channelKey);
+			mapped = true;
 		}
 		if (this.prefix != null) {
 			channelName = this.prefix + channelName;
@@ -220,6 +258,9 @@ public abstract class AbstractMappingMessageRouter extends AbstractMessageRouter
 		MessageChannel channel = resolveChannelForName(channelName, message);
 		if (channel != null) {
 			channels.add(channel);
+			if (!mapped && !(this.dynamicChannels.get(channelName) != null)) {
+				this.dynamicChannels.put(channelName, channel);
+			}
 		}
 	}
 

spring-integration-core/src/main/java/org/springframework/integration/router/AbstractMessageRouter.java

@@ -43,7 +43,7 @@ import org.springframework.util.Assert;
  */
 @ManagedResource
 @IntegrationManagedResource
-public abstract class AbstractMessageRouter extends AbstractMessageHandler {
+public abstract class AbstractMessageRouter extends AbstractMessageHandler implements MessageRouter {
 
 	private volatile MessageChannel defaultOutputChannel;
 
@@ -69,6 +69,24 @@ public abstract class AbstractMessageRouter extends AbstractMessageHandler {
 		this.defaultOutputChannel = defaultOutputChannel;
 	}
 
+	/**
+	 * Get the default output channel.
+	 * @return the channel.
+	 * @since 4.3
+	 */
+	@Override
+	public MessageChannel getDefaultOutputChannel() {
+		if (this.defaultOutputChannelName != null) {
+			synchronized (this) {
+				if (this.defaultOutputChannelName != null) {
+					this.defaultOutputChannel = getChannelResolver().resolveDestination(this.defaultOutputChannelName);
+					this.defaultOutputChannelName = null;
+				}
+			}
+		}
+		return this.defaultOutputChannel;
+	}
+
 	public void setDefaultOutputChannelName(String defaultOutputChannelName) {
 		Assert.hasText(defaultOutputChannelName, "'defaultOutputChannelName' must not be empty");
 		this.defaultOutputChannelName = defaultOutputChannelName;
@@ -188,14 +206,7 @@ public abstract class AbstractMessageRouter extends AbstractMessageHandler {
 			}
 		}
 		if (!sent) {
-			if (this.defaultOutputChannelName != null) {
-				synchronized (this) {
-					if (this.defaultOutputChannelName != null) {
-						this.defaultOutputChannel = getChannelResolver().resolveDestination(this.defaultOutputChannelName);
-						this.defaultOutputChannelName = null;
-					}
-				}
-			}
+			getDefaultOutputChannel();
 			if (this.defaultOutputChannel != null) {
 				this.messagingTemplate.send(this.defaultOutputChannel, message);
 			}

spring-integration-core/src/main/java/org/springframework/integration/router/ExpressionEvaluatingRouter.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.
@@ -25,12 +25,14 @@ import org.springframework.integration.handler.ExpressionEvaluatingMessageProces
  * resolved to a channel name or a Collection (or Array) of strings.
  *
  * @author Mark Fisher
+ * @author Gary Russell
  * @since 2.0
  */
 public class ExpressionEvaluatingRouter extends AbstractMessageProcessingRouter {
 
 	public ExpressionEvaluatingRouter(Expression expression) {
 		super(new ExpressionEvaluatingMessageProcessor<Object>(expression));
+		setPrimaryExpression(expression);
 	}
 
 }

spring-integration-core/src/main/java/org/springframework/integration/router/MessageRouter.java

@@ -0,0 +1,36 @@
+/*
+ * 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.router;
+
+import org.springframework.messaging.MessageChannel;
+
+/**
+ * Routers implementing this interface have a default output channel.
+ *
+ * @author Gary Russell
+ * @since 4.3
+ *
+ */
+public interface MessageRouter {
+
+	/**
+	 * Get the default output channel.
+	 * @return the channel.
+	 */
+	MessageChannel getDefaultOutputChannel();
+
+}

spring-integration-core/src/main/java/org/springframework/integration/splitter/ExpressionEvaluatingSplitter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2014 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.
@@ -34,6 +34,7 @@ public class ExpressionEvaluatingSplitter extends AbstractMessageProcessingSplit
 	@SuppressWarnings({"unchecked", "rawtypes"})
 	public ExpressionEvaluatingSplitter(Expression expression) {
 		super(new ExpressionEvaluatingMessageProcessor(expression));
+		setPrimaryExpression(expression);
 	}
 
 }

spring-integration-core/src/main/java/org/springframework/integration/support/management/MappingMessageRouterManagement.java

@@ -16,6 +16,7 @@
 
 package org.springframework.integration.support.management;
 
+import java.util.Collection;
 import java.util.Map;
 import java.util.Properties;
 
@@ -53,7 +54,6 @@ public interface MappingMessageRouterManagement {
 	/**
 	 * Provide mappings from channel keys to channel names.
 	 * @param channelMappings The channel mappings.
-	 *
 	 * @since 4.0
 	 */
 	@ManagedOperation
@@ -61,7 +61,6 @@ public interface MappingMessageRouterManagement {
 
 	/**
 	 * @return an unmodifiable map of channel mappings.
-	 *
 	 * @since 4.0
 	 */
 	@ManagedAttribute
@@ -70,12 +69,21 @@ public interface MappingMessageRouterManagement {
 	/**
 	 * Provide mappings from channel keys to channel names.
 	 * Channel names will be resolved by the {@link DestinationResolver}.
-	 *
 	 * @param channelMappings The channel mappings.
-	 *
 	 * @since 4.0
 	 */
 	@ManagedAttribute
 	void setChannelMappings(Map<String, String> channelMappings);
 
+	/**
+	 * Provide a collection of channel names to which
+	 * we have routed messages where the channel was not explicitly mapped.
+	 * <p> Implementations may choose to return only the most recent channel names.
+	 * @return a collection of channel names to which
+	 * we have routed messages where the channel was not explicitly mapped.
+	 * @since 4.3
+	 */
+	@ManagedAttribute
+	Collection<String> getDynamicChannelNames();
+
 }

spring-integration-core/src/main/java/org/springframework/integration/support/management/RouterMetrics.java

@@ -16,6 +16,7 @@
 
 package org.springframework.integration.support.management;
 
+import java.util.Collection;
 import java.util.Map;
 import java.util.Properties;
 
@@ -62,4 +63,9 @@ public class RouterMetrics extends LifecycleMessageHandlerMetrics implements Map
 		this.router.setChannelMappings(channelMappings);
 	}
 
+	@Override
+	public Collection<String> getDynamicChannelNames() {
+		return this.router.getDynamicChannelNames();
+	}
+
 }

spring-integration-core/src/main/java/org/springframework/integration/support/management/graph/ErrorCapableRoutingNode.java

@@ -0,0 +1,46 @@
+/*
+ * 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.support.management.graph;
+
+import java.util.Collection;
+
+import org.springframework.messaging.MessageHandler;
+
+/**
+ * Represents an endpoint that can route to multiple channels and can emit errors
+ * (pollable endpoint).
+ *
+ * @author Gary Russell
+ * @since 4.3
+ *
+ */
+public class ErrorCapableRoutingNode extends RoutingMessageHandlerNode implements ErrorCapableNode {
+
+	private final String errors;
+
+	public ErrorCapableRoutingNode(int nodeId, String name, MessageHandler handler, String input, String output,
+			String errors, Collection<String> routes) {
+		super(nodeId, name, handler, input, output, routes);
+		this.errors = errors;
+	}
+
+	@Override
+	public String getErrors() {
+		return this.errors;
+	}
+
+}

spring-integration-core/src/main/java/org/springframework/integration/support/management/graph/IntegrationGraphServer.java

@@ -38,7 +38,10 @@ import org.springframework.integration.gateway.GatewayProxyFactoryBean;
 import org.springframework.integration.gateway.MessagingGatewaySupport;
 import org.springframework.integration.handler.CompositeMessageHandler;
 import org.springframework.integration.handler.DiscardingMessageHandler;
+import org.springframework.integration.router.RecipientListRouter.Recipient;
+import org.springframework.integration.router.RecipientListRouterManagement;
 import org.springframework.integration.support.context.NamedComponent;
+import org.springframework.integration.support.management.MappingMessageRouterManagement;
 import org.springframework.messaging.MessageChannel;
 import org.springframework.messaging.MessageHandler;
 import org.springframework.util.StringUtils;
@@ -172,8 +175,14 @@ public class IntegrationGraphServer implements ApplicationContextAware, Applicat
 			for (Entry<Method, MessagingGatewaySupport> gwEntry : methodMap.entrySet()) {
 				MessagingGatewaySupport gateway = gwEntry.getValue();
 				Method method = gwEntry.getKey();
+				Class<?>[] parameterTypes = method.getParameterTypes();
+				String[] parameterTypeNames = new String[parameterTypes.length];
+				int i = 0;
+				for (Class<?> type : parameterTypes) {
+					parameterTypeNames[i++] = type.getName();
+				}
 				String signature = method.getName() +
-						"(" + StringUtils.arrayToCommaDelimitedString(method.getParameterTypes()) + ")";
+						"(" + StringUtils.arrayToCommaDelimitedString(parameterTypeNames) + ")";
 				MessageGatewayNode gatewayNode = this.nodeFactory.gatewayNode(
 						entry.getKey().substring(1) + "." + signature, gateway);
 				nodes.add(gatewayNode);
@@ -232,6 +241,15 @@ public class IntegrationGraphServer implements ApplicationContextAware, Applicat
 				links.add(new LinkNode(endpointNode.getNodeId(), channelNode.getNodeId(), LinkNode.Type.discard));
 			}
 		}
+		if (endpointNode instanceof RoutingMessageHandlerNode) {
+			Collection<String> routes = ((RoutingMessageHandlerNode) endpointNode).getRoutes();
+			for (String route : routes) {
+				channelNode = channelNodes.get(route);
+				if (channelNode != null) {
+					links.add(new LinkNode(endpointNode.getNodeId(), channelNode.getNodeId(), LinkNode.Type.route));
+				}
+			}
+		}
 	}
 
 	/**
@@ -275,13 +293,26 @@ public class IntegrationGraphServer implements ApplicationContextAware, Applicat
 			MessageChannel outputChannel = consumer.getOutputChannel();
 			String outputChannelName = outputChannel == null ? null : outputChannel.toString();
 			MessageHandler handler = consumer.getHandler();
-			return handler instanceof CompositeMessageHandler
-					? compositeHandler(name, consumer, (CompositeMessageHandler) handler, outputChannelName, null, false)
-					: handler instanceof DiscardingMessageHandler
-					? discardingHandler(name, consumer, (DiscardingMessageHandler) handler, outputChannelName, null,
-					false)
-					: new MessageHandlerNode(this.nodeId.incrementAndGet(), name, handler,
-					consumer.getInputChannel().toString(), outputChannelName);
+			if (handler instanceof CompositeMessageHandler) {
+				return compositeHandler(name, consumer, (CompositeMessageHandler) handler, outputChannelName, null,
+							false);
+			}
+			else if (handler instanceof DiscardingMessageHandler) {
+				return discardingHandler(name, consumer, (DiscardingMessageHandler) handler, outputChannelName, null,
+							false);
+			}
+			else if (handler instanceof MappingMessageRouterManagement) {
+				return routingHandler(name, consumer, handler, (MappingMessageRouterManagement) handler,
+							outputChannelName, null, false);
+			}
+			else if (handler instanceof RecipientListRouterManagement) {
+				return recipientListRoutingHandler(name, consumer, handler, (RecipientListRouterManagement) handler,
+							outputChannelName, null, false);
+			}
+			else {
+				return new MessageHandlerNode(this.nodeId.incrementAndGet(), name, handler,
+							consumer.getInputChannel().toString(), outputChannelName);
+			}
 		}
 
 		private MessageHandlerNode polledHandlerNode(String name, PollingConsumer consumer) {
@@ -290,14 +321,26 @@ public class IntegrationGraphServer implements ApplicationContextAware, Applicat
 			String errorChannel = consumer.getDefaultErrorChannel() != null
 					? consumer.getDefaultErrorChannel().toString() : null;
 			MessageHandler handler = consumer.getHandler();
-			return handler instanceof CompositeMessageHandler
-					? compositeHandler(name, consumer, (CompositeMessageHandler) handler, outputChannelName, errorChannel,
-					true)
-					: handler instanceof DiscardingMessageHandler
-					? discardingHandler(name, consumer, (DiscardingMessageHandler) handler, outputChannelName,
-					errorChannel, true)
-					: new ErrorCapableMessageHandlerNode(this.nodeId.incrementAndGet(), name, handler,
-					consumer.getInputChannel().toString(), outputChannelName, errorChannel);
+			if (handler instanceof CompositeMessageHandler) {
+				return compositeHandler(name, consumer, (CompositeMessageHandler) handler, outputChannelName,
+							errorChannel, true);
+			}
+			else if (handler instanceof DiscardingMessageHandler) {
+				return discardingHandler(name, consumer, (DiscardingMessageHandler) handler, outputChannelName,
+							errorChannel, true);
+			}
+			else if (handler instanceof MappingMessageRouterManagement) {
+				return routingHandler(name, consumer, handler, (MappingMessageRouterManagement) handler,
+							outputChannelName, errorChannel, true);
+			}
+			else if (handler instanceof RecipientListRouterManagement) {
+				return recipientListRoutingHandler(name, consumer, handler, (RecipientListRouterManagement) handler,
+							outputChannelName, errorChannel, true);
+			}
+			else {
+				return new ErrorCapableMessageHandlerNode(this.nodeId.incrementAndGet(), name, handler,
+							consumer.getInputChannel().toString(), outputChannelName, errorChannel);
+			}
 		}
 
 		private MessageHandlerNode compositeHandler(String name, IntegrationConsumer consumer,
@@ -314,18 +357,48 @@ public class IntegrationGraphServer implements ApplicationContextAware, Applicat
 			}
 			return polled
 					? new ErrorCapableCompositeMessageHandlerNode(this.nodeId.incrementAndGet(), name, handler,
-					consumer.getInputChannel().toString(), output, errors, innerHandlers)
+						consumer.getInputChannel().toString(), output, errors, innerHandlers)
 					: new CompositeMessageHandlerNode(this.nodeId.incrementAndGet(), name, handler,
-					consumer.getInputChannel().toString(), output, innerHandlers);
+						consumer.getInputChannel().toString(), output, innerHandlers);
 		}
 
 		private MessageHandlerNode discardingHandler(String name, IntegrationConsumer consumer,
 				DiscardingMessageHandler handler, String output, String errors, boolean polled) {
 			return polled
 					? new ErrorCapableDiscardingMessageHandlerNode(this.nodeId.incrementAndGet(), name, handler,
-					consumer.getInputChannel().toString(), output, handler.getDiscardChannel().toString(), errors)
+						consumer.getInputChannel().toString(), output, handler.getDiscardChannel().toString(), errors)
 					: new DiscardingMessageHandlerNode(this.nodeId.incrementAndGet(), name, handler,
-					consumer.getInputChannel().toString(), output, handler.getDiscardChannel().toString());
+						consumer.getInputChannel().toString(), output, handler.getDiscardChannel().toString());
+		}
+
+		private MessageHandlerNode routingHandler(String name, IntegrationConsumer consumer, MessageHandler handler,
+				MappingMessageRouterManagement router, String output, String errors, boolean polled) {
+			Collection<String> routes = router.getChannelMappings().values();
+			Collection<String> dynamicChannelNames = router.getDynamicChannelNames();
+			if (dynamicChannelNames.size() > 0) {
+				routes = new ArrayList<String>(routes);
+				routes.addAll(dynamicChannelNames);
+			}
+			return polled
+					? new ErrorCapableRoutingNode(this.nodeId.incrementAndGet(), name, handler,
+						consumer.getInputChannel().toString(), output, errors, routes)
+					: new RoutingMessageHandlerNode(this.nodeId.incrementAndGet(), name, handler,
+						consumer.getInputChannel().toString(), output, routes);
+		}
+
+		private MessageHandlerNode recipientListRoutingHandler(String name, IntegrationConsumer consumer,
+				MessageHandler handler, RecipientListRouterManagement router, String output, String errors,
+				boolean polled) {
+			Collection<?> recipients = router.getRecipients();
+			List<String> routes = new ArrayList<String>(recipients.size());
+			for (Object recipient : recipients) {
+				routes.add(((Recipient) recipient).getChannel().toString());
+			}
+			return polled
+					? new ErrorCapableRoutingNode(this.nodeId.incrementAndGet(), name, handler,
+						consumer.getInputChannel().toString(), output, errors, routes)
+					: new RoutingMessageHandlerNode(this.nodeId.incrementAndGet(), name, handler,
+						consumer.getInputChannel().toString(), output, routes);
 		}
 
 		private void reset() {

spring-integration-core/src/main/java/org/springframework/integration/support/management/graph/IntegrationNode.java

@@ -16,6 +16,11 @@
 
 package org.springframework.integration.support.management.graph;
 
+import java.util.HashMap;
+import java.util.Map;
+
+import org.springframework.expression.Expression;
+import org.springframework.integration.context.ExpressionCapable;
 import org.springframework.integration.support.context.NamedComponent;
 
 /**
@@ -35,12 +40,20 @@ public abstract class IntegrationNode {
 
 	private final String componentType;
 
+	private final Map<String, Object> properties = new HashMap<String, Object>();
+
 	protected IntegrationNode(int nodeId, String name, Object nodeObject, Stats stats) {
 		this.nodeId = nodeId;
 		this.name = name;
 		this.componentType = nodeObject instanceof NamedComponent ? ((NamedComponent) nodeObject).getComponentType()
 				: nodeObject.getClass().getSimpleName();
 		this.stats = stats;
+		if (nodeObject instanceof ExpressionCapable) {
+			Expression expression = ((ExpressionCapable) nodeObject).getExpression();
+			if (expression != null) {
+				this.properties.put("expression", expression.getExpressionString());
+			}
+		}
 	}
 
 	public int getNodeId() {
@@ -59,6 +72,10 @@ public abstract class IntegrationNode {
 		return this.stats.isAvailable() ? this.stats : null;
 	}
 
+	public Map<String, Object> getProperties() {
+		return this.properties.size() == 0 ? null : this.properties;
+	}
+
 	public static class Stats {
 
 		protected boolean isAvailable() {

spring-integration-core/src/main/java/org/springframework/integration/support/management/graph/LinkNode.java

@@ -50,7 +50,7 @@ public class LinkNode {
 	}
 
 	public enum Type {
-		input, output, error, discard
+		input, output, error, discard, route
 	}
 
 }

spring-integration-core/src/main/java/org/springframework/integration/support/management/graph/RoutingMessageHandlerNode.java

@@ -0,0 +1,44 @@
+/*
+ * 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.support.management.graph;
+
+import java.util.Collection;
+
+import org.springframework.messaging.MessageHandler;
+
+/**
+ * Represents an endpoint that can route to multiple channels.
+ *
+ * @author Gary Russell
+ * @since 4.3
+ *
+ */
+public class RoutingMessageHandlerNode extends MessageHandlerNode {
+
+	private final Collection<String> routes;
+
+	public RoutingMessageHandlerNode(int nodeId, String name, MessageHandler handler, String input, String output,
+			Collection<String> routes) {
+		super(nodeId, name, handler, input, output);
+		this.routes = routes;
+	}
+
+	public Collection<String> getRoutes() {
+		return this.routes;
+	}
+
+}

spring-integration-core/src/test/java/org/springframework/integration/router/HeaderValueRouterTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2011 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.
@@ -16,10 +16,14 @@
 
 package org.springframework.integration.router;
 
+import static org.hamcrest.Matchers.contains;
+import static org.hamcrest.Matchers.equalTo;
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertSame;
+import static org.junit.Assert.assertThat;
 
 import org.junit.Test;
+
 import org.springframework.beans.factory.support.ManagedMap;
 import org.springframework.beans.factory.support.RootBeanDefinition;
 import org.springframework.context.support.StaticApplicationContext;
@@ -33,6 +37,7 @@ import org.springframework.messaging.core.DestinationResolver;
 /**
  * @author Mark Fisher
  * @author Oleg Zhurakousky
+ * @author Gary Russell
  */
 public class HeaderValueRouterTests {
 
@@ -51,6 +56,7 @@ public class HeaderValueRouterTests {
 		Message<?> result = testChannel.receive(1000);
 		assertNotNull(result);
 		assertSame(message, result);
+		context.close();
 	}
 
 	@Test
@@ -84,6 +90,7 @@ public class HeaderValueRouterTests {
 		result = channel.receive(1000);
 		assertNotNull(result);
 		assertSame(message, result);
+		context.close();
 	}
 
 	@Test
@@ -107,7 +114,9 @@ public class HeaderValueRouterTests {
 		Message<?> result = channel.receive(1000);
 		assertNotNull(result);
 		assertSame(message, result);
+		context.close();
 	}
+
 	@Test
 	@SuppressWarnings({ "unchecked", "rawtypes" })
 	public void resolveChannelNameFromMapAndCustomeResolver() {
@@ -120,6 +129,7 @@ public class HeaderValueRouterTests {
 		routerBeanDefinition.getPropertyValues().addPropertyValue("channelMappings", channelMappings);
 		routerBeanDefinition.getPropertyValues().addPropertyValue("beanFactory", context);
 		routerBeanDefinition.getPropertyValues().addPropertyValue("channelResolver", new DestinationResolver<MessageChannel>() {
+			@Override
 			public MessageChannel resolveDestination(String channelName) {
 				return context.getBean("anotherChannel", MessageChannel.class);
 			}
@@ -135,6 +145,7 @@ public class HeaderValueRouterTests {
 		Message<?> result = channel.receive(1000);
 		assertNotNull(result);
 		assertSame(message, result);
+		context.close();
 	}
 
 	@Test
@@ -159,6 +170,7 @@ public class HeaderValueRouterTests {
 		assertNotNull(result2);
 		assertSame(message, result1);
 		assertSame(message, result2);
+		context.close();
 	}
 
 	@Test
@@ -183,7 +195,33 @@ public class HeaderValueRouterTests {
 		assertNotNull(result2);
 		assertSame(message, result1);
 		assertSame(message, result2);
+		context.close();
 	}
 
+	@Test
+	public void dynamicChannelCache() {
+		StaticApplicationContext context = new StaticApplicationContext();
+		RootBeanDefinition routerBeanDefinition = new RootBeanDefinition(HeaderValueRouter.class);
+		routerBeanDefinition.getConstructorArgumentValues().addGenericArgumentValue("testHeaderName");
+		routerBeanDefinition.getPropertyValues().addPropertyValue("resolutionRequired", "true");
+		routerBeanDefinition.getPropertyValues().addPropertyValue("dynamicChannelLimit", "2");
+		context.registerBeanDefinition("router", routerBeanDefinition);
+		context.registerBeanDefinition("channel1", new RootBeanDefinition(QueueChannel.class));
+		context.registerBeanDefinition("channel2", new RootBeanDefinition(QueueChannel.class));
+		context.registerBeanDefinition("channel3", new RootBeanDefinition(QueueChannel.class));
+		context.refresh();
+		MessageHandler handler = (MessageHandler) context.getBean("router");
+		String channels = "channel1, channel2, channel1, channel3";
+		Message<?> message = MessageBuilder.withPayload("test").setHeader("testHeaderName", channels).build();
+		handler.handleMessage(message);
+		QueueChannel channel1 = (QueueChannel) context.getBean("channel1");
+		QueueChannel channel2 = (QueueChannel) context.getBean("channel2");
+		QueueChannel channel3 = (QueueChannel) context.getBean("channel3");
+		assertThat(channel1.getQueueSize(), equalTo(2));
+		assertThat(channel2.getQueueSize(), equalTo(1));
+		assertThat(channel3.getQueueSize(), equalTo(1));
+		assertThat(context.getBean(HeaderValueRouter.class).getDynamicChannelNames(), contains("channel1", "channel3"));
+		context.close();
+	}
 
 }

spring-integration-core/src/test/java/org/springframework/integration/support/management/graph/IntegrationGraphServerTests.java

@@ -22,6 +22,7 @@ import static org.hamcrest.Matchers.notNullValue;
 import static org.junit.Assert.assertThat;
 
 import java.io.ByteArrayOutputStream;
+import java.util.Arrays;
 import java.util.List;
 import java.util.Map;
 
@@ -32,8 +33,10 @@ import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.ImportResource;
+import org.springframework.expression.spel.standard.SpelExpressionParser;
 import org.springframework.integration.annotation.IntegrationComponentScan;
 import org.springframework.integration.annotation.MessagingGateway;
+import org.springframework.integration.annotation.Router;
 import org.springframework.integration.annotation.ServiceActivator;
 import org.springframework.integration.channel.DirectChannel;
 import org.springframework.integration.channel.MessagePublishingErrorHandler;
@@ -44,8 +47,13 @@ import org.springframework.integration.core.MessageProducer;
 import org.springframework.integration.endpoint.EventDrivenConsumer;
 import org.springframework.integration.endpoint.MessageProducerSupport;
 import org.springframework.integration.endpoint.PollingConsumer;
+import org.springframework.integration.router.ExpressionEvaluatingRouter;
+import org.springframework.integration.router.HeaderValueRouter;
+import org.springframework.integration.router.RecipientListRouter;
 import org.springframework.integration.scheduling.PollerMetadata;
+import org.springframework.integration.support.MessageBuilder;
 import org.springframework.messaging.Message;
+import org.springframework.messaging.MessageChannel;
 import org.springframework.messaging.MessageHandler;
 import org.springframework.messaging.MessagingException;
 import org.springframework.messaging.PollableChannel;
@@ -69,6 +77,10 @@ public class IntegrationGraphServerTests {
 	@Autowired
 	private IntegrationGraphServer server;
 
+	@Autowired
+	private MessageChannel toRouter;
+
+	@SuppressWarnings("unchecked")
 	@Test
 	public void test() throws Exception {
 		Graph graph = this.server.getGraph();
@@ -76,17 +88,39 @@ public class IntegrationGraphServerTests {
 		ObjectMapper objectMapper = new ObjectMapper();
 		objectMapper.enable(SerializationFeature.INDENT_OUTPUT);
 		objectMapper.writeValue(baos, graph);
+
 //		System . out . println(new String(baos.toByteArray()));
+
 		Map<?, ?> map = objectMapper.readValue(baos.toByteArray(), Map.class);
 		assertThat(map.size(), is(equalTo(3)));
-		@SuppressWarnings("unchecked")
 		List<Map<?, ?>> nodes = (List<Map<?, ?>>) map.get("nodes");
 		assertThat(nodes, is(notNullValue()));
-		assertThat(nodes.size(), is(equalTo(22)));
-		@SuppressWarnings("unchecked")
+		assertThat(nodes.size(), is(equalTo(31)));
 		List<Map<?, ?>> links = (List<Map<?, ?>>) map.get("links");
 		assertThat(links, is(notNullValue()));
-		assertThat(links.size(), is(equalTo(20)));
+		assertThat(links.size(), is(equalTo(32)));
+
+		toRouter.send(MessageBuilder.withPayload("foo").setHeader("foo", "bar").build());
+		toRouter.send(MessageBuilder.withPayload("foo").setHeader("foo", "baz").build());
+		toRouter.send(MessageBuilder.withPayload("foo").setHeader("foo", "quxChannel").build());
+		toRouter.send(MessageBuilder.withPayload("foo").setHeader("foo", "fizChannel").build());
+
+		this.server.rebuild();
+		graph = this.server.getGraph();
+		baos = new ByteArrayOutputStream();
+		objectMapper.enable(SerializationFeature.INDENT_OUTPUT);
+		objectMapper.writeValue(baos, graph);
+
+//		System . out . println(new String(baos.toByteArray()));
+
+		map = objectMapper.readValue(baos.toByteArray(), Map.class);
+		assertThat(map.size(), is(equalTo(3)));
+		nodes = (List<Map<?, ?>>) map.get("nodes");
+		assertThat(nodes, is(notNullValue()));
+		assertThat(nodes.size(), is(equalTo(31)));
+		links = (List<Map<?, ?>>) map.get("links");
+		assertThat(links, is(notNullValue()));
+		assertThat(links.size(), is(equalTo(34)));
 	}
 
 	@Configuration
@@ -165,6 +199,64 @@ public class IntegrationGraphServerTests {
 			return poller;
 		}
 
+		@Bean
+		@Router(inputChannel = "toRouter")
+		public HeaderValueRouter router() {
+			HeaderValueRouter router = new HeaderValueRouter("foo");
+			router.setChannelMapping("bar", "barChannel");
+			router.setChannelMapping("baz", "bazChannel");
+			router.setDefaultOutputChannel(discards());
+			return router;
+		}
+
+		@Bean
+		@Router(inputChannel = "four")
+		public RecipientListRouter rlRouter() {
+			RecipientListRouter router = new RecipientListRouter();
+			router.setChannels(Arrays.asList(barChannel(), bazChannel()));
+			router.setDefaultOutputChannel(discards());
+			return router;
+		}
+
+		@Bean
+		@Router(inputChannel = "four")
+		public ExpressionEvaluatingRouter expressionRouter() {
+			ExpressionEvaluatingRouter router = new ExpressionEvaluatingRouter(
+					new SpelExpressionParser().parseExpression("headers['foo']"));
+			router.setDefaultOutputChannel(discards());
+			return router;
+		}
+
+		@Bean
+		public MessageChannel discards() {
+			return new DirectChannel();
+		}
+
+		@Bean
+		public MessageChannel toRouter() {
+			return new DirectChannel();
+		}
+
+		@Bean
+		public MessageChannel barChannel() {
+			return new QueueChannel();
+		}
+
+		@Bean
+		public MessageChannel bazChannel() {
+			return new QueueChannel();
+		}
+
+		@Bean
+		public MessageChannel quxChannel() {
+			return new QueueChannel();
+		}
+
+		@Bean
+		public MessageChannel fizChannel() {
+			return new QueueChannel();
+		}
+
 	}
 
 	public static class Services {

spring-integration-file/src/main/java/org/springframework/integration/file/remote/gateway/AbstractRemoteFileOutboundGateway.java

@@ -307,9 +307,11 @@ public abstract class AbstractRemoteFileOutboundGateway<F> extends AbstractReply
 		Assert.notNull(remoteFileTemplate, "'remoteFileTemplate' cannot be null");
 		this.remoteFileTemplate = remoteFileTemplate;
 		this.command = command;
+		Expression parsedExpression = new SpelExpressionParser().parseExpression(expression);
 		this.fileNameProcessor = new ExpressionEvaluatingMessageProcessor<String>(
-			new SpelExpressionParser().parseExpression(expression));
+			parsedExpression);
 		this.messageSessionCallback = null;
+		setPrimaryExpression(parsedExpression);
 	}
 
 	/**

spring-integration-jms/src/main/java/org/springframework/integration/jms/JmsOutboundGateway.java

@@ -217,6 +217,7 @@ public class JmsOutboundGateway extends AbstractReplyProducingMessageHandler imp
 		Assert.notNull(requestDestinationExpression, "'requestDestinationExpression' must not be null");
 		this.requestDestinationExpressionProcessor =
 				new ExpressionEvaluatingMessageProcessor<Object>(requestDestinationExpression);
+		setPrimaryExpression(requestDestinationExpression);
 	}
 
 	/**

spring-integration-jms/src/main/java/org/springframework/integration/jms/JmsSendingMessageHandler.java

@@ -70,6 +70,7 @@ public class JmsSendingMessageHandler extends AbstractMessageHandler {
 		Assert.isTrue(this.destination == null && this.destinationName == null,
 				"The 'destination', 'destinationName', and 'destinationExpression' properties are mutually exclusive.");
 		this.destinationExpressionProcessor = new ExpressionEvaluatingMessageProcessor<Object>(destinationExpression);
+		setPrimaryExpression(destinationExpression);
 	}
 
 	public void setHeaderMapper(JmsHeaderMapper headerMapper) {

src/reference/asciidoc/graph.adoc

@@ -84,6 +84,10 @@ The possible types are:
 - _output_ - the direction from `MessageHandler`, `MessageProducer` or `SourcePollingChannelAdapter` to the `MessageChannel` via an `outputChannel` or `replyChannel` property;
 - _error_ - from `MessageHandler` on `PollingConsumer` or `MessageProducer` or `SourcePollingChannelAdapter` to the `MessageChannel` via an `errorChannel` property;
 - _discard_ - from `DiscardingMessageHandler` (e.g. `MessageFilter`) to the `MessageChannel` via `errorChannel` property.
+- _route_ - from `AbstractMappingMessageRouter` (e.g. `HeaderValueRouter`) to the `MessageChannel`.
+Similar to _output_ but determined at run-time.
+May be a configured channel mapping, or a dynamically resolved channel.
+Routers will typically only retain up to 100 dynamic routes for this purpose, but this can be modified using the `dynamicChannelLimit` property.
 
 The information from this element can be used by a visualizing tool to render connections between nodes from the `nodes` graph element, where the `from` and `to` numbers represent the value from the `nodeId` property of the linked nodes.
 For example the link `type` can be used to determine the proper _port_ on the target node:
@@ -105,6 +109,8 @@ For example the link `type` can be used to determine the proper _port_ on the ta
 ----
 
 The `nodes` graph element is perhaps the most interesting because its elements contain not only the runtime components with their `componentType` s and `name` s, but can also optionally contain metrics exposed by the component.
+Node elements contain various properties which are generally self-explanatory.
+For example, expression-based components include the `expression` property containing the primary expression string for the component.
 To enable the metrics, add an `@EnableIntegrationManagement` to some `@Configuration` class or add an `<int:management/>` element to your XML configuration.
 You can control exactly which components in the framework collect statistics.
 See  <<metrics-management>> for complete information.