8. System Management

8.1 JMX Support

Spring Integration provides Channel Adapters for receiving and publishing JMX Notifications. There is also an Inbound Channel Adapter for polling JMX MBean attribute values, and an Outbound Channel Adapter for invoking JMX MBean operations.

8.1.1 Notification Listening Channel Adapter

The Notification-listening Channel Adapter requires a JMX ObjectName for the MBean that publishes notifications to which this listener should be registered. A very simple configuration might look like this:

<int-jmx:notification-listening-channel-adapter id="adapter"
    channel="channel"
    object-name="example.domain:name=publisher"/>
[Tip]Tip
The notification-listening-channel-adapter registers with an MBeanServer at startup, and the default bean name is mbeanServer which happens to be the same bean name generated when using Spring's <context:mbean-server/> element. If you need to use a different name, be sure to include the mbean-server attribute.

The adapter can also accept a reference to a NotificationFilter and a handback Object to provide some context that is passed back with each Notification. Both of those attributes are optional. Extending the above example to include those attributes as well as an explicit MBeanServer bean name would produce the following:

<int-jmx:notification-listening-channel-adapter id="adapter"
    channel="channel"
    mbean-server="someServer"
    object-name="example.domain:name=somePublisher"
    notification-filter="notificationFilter"
    handback="myHandback"/>

The Notification-listening Channel Adapter is event-driven and registered with the MBeanServer directly. It does not require any poller configuration.

[Note]Note
For this component only, the object-name attribute can contain an ObjectName pattern (e.g. "org.foo:type=Bar,name=*") and the adapter will receive notifications from all MBeans with ObjectNames that match the pattern. In addition, the object-name attribute can contain a SpEL reference to a <util:list/> of ObjectName patterns:
<jmx:notification-listening-channel-adapter id="manyNotificationsAdapter"
    channel="manyNotificationsChannel"
    object-name="#{patterns}"/>

<util:list id="patterns">
    <value>org.foo:type=Foo,name=*</value>
    <value>org.foo:type=Bar,name=*</value>
</util:list>
The names of the located MBean(s) will be logged when DEBUG level logging is enabled.

8.1.2 Notification Publishing Channel Adapter

The Notification-publishing Channel Adapter is relatively simple. It only requires a JMX ObjectName in its configuration as shown below.

<context:mbean-export/>

<int-jmx:notification-publishing-channel-adapter id="adapter"
    channel="channel"
    object-name="example.domain:name=publisher"/>

It does also require that an MBeanExporter be present in the context. That is why the <context:mbean-export/> element is shown above as well.

When Messages are sent to the channel for this adapter, the Notification is created from the Message content. If the payload is a String it will be passed as the message text for the Notification. Any other payload type will be passed as the userData of the Notification.

JMX Notifications also have a type, and it should be a dot-delimited String. There are two ways to provide the type. Precedence will always be given to a Message header value associated with the JmxHeaders.NOTIFICATION_TYPE key. On the other hand, you can rely on a fallback default-notification-type attribute provided in the configuration.

<context:mbean-export/>

<int-jmx:notification-publishing-channel-adapter id="adapter"
    channel="channel"
    object-name="example.domain:name=publisher"
    default-notification-type="some.default.type"/>

8.1.3 Attribute Polling Channel Adapter

The Attribute Polling Channel Adapter is useful when you have a requirement, to periodically check on some value that is available through an MBean as a managed attribute. The poller can be configured in the same way as any other polling adapter in Spring Integration (or it's possible to rely on the default poller). The object-name and attribute-name are required. An MBeanServer reference is also required, but it will automatically check for a bean named mbeanServer by default, just like the Notification-listening Channel Adapter described above.

<int-jmx:attribute-polling-channel-adapter id="adapter"
    channel="channel"
    object-name="example.domain:name=someService"
    attribute-name="InvocationCount">
        <int:poller max-messages-per-poll="1" fixed-rate="5000"/>
</int-jmx:attribute-polling-channel-adapter>

8.1.4 Tree Polling Channel Adapter

The Tree Polling Channel Adapter queries the JMX MBean tree and sends a message with a payload that is the graph of objects that matches the query. By default the MBeans are mapped to primitives and simple Objects like Map, List and arrays - permitting simple transformation, for example, to JSON. An MBeanServer reference is also required, but it will automatically check for a bean named mbeanServer by default, just like the Notification-listening Channel Adapter described above. A basic configuration would be:

<int-jmx:tree-polling-channel-adapter id="adapter"
    channel="channel"
    query-name="example.domain:type=*">
        <int:poller max-messages-per-poll="1" fixed-rate="5000"/>
</int-jmx:tree-polling-channel-adapter>

This will include all attributes on the MBeans selected. You can filter the attributes by providing an MBeanObjectConverter that has an appropriate filter configured. The converter can be provided as a reference to a bean definition using the converter attribute, or as an inner <bean/> definition. A DefaultMBeanObjectConverter is provided which can take a MBeanAttributeFilter in its constructor argument.

Two standard filters are provided; the NamedFieldsMBeanAttributeFilter allows you to specify a list of attributes to include and the NotNamedFieldsMBeanAttributeFilter allows you to specify a list of attributes to exclude. You can also implement your own filter

8.1.5 Operation Invoking Channel Adapter

The operation-invoking-channel-adapter enables Message-driven invocation of any managed operation exposed by an MBean. Each invocation requires the operation name to be invoked and the ObjectName of the target MBean. Both of these must be explicitly provided via adapter configuration:

<int-jmx:operation-invoking-channel-adapter id="adapter"
    object-name="example.domain:name=TestBean"
    operation-name="ping"/>

Then the adapter only needs to be able to discover the mbeanServer bean. If a different bean name is required, then provide the mbean-server attribute with a reference.

The payload of the Message will be mapped to the parameters of the operation, if any. A Map-typed payload with String keys is treated as name/value pairs, whereas a List or array would be passed as a simple argument list (with no explicit parameter names). If the operation requires a single parameter value, then the payload can represent that single value, and if the operation requires no parameters, then the payload would be ignored.

If you want to expose a channel for a single common operation to be invoked by Messages that need not contain headers, then that option works well.

8.1.6 Operation Invoking Outbound Gateway

Similar to the operation-invoking-channel-adapter Spring Integration also provides a operation-invoking-outbound-gateway, which could be used when dealing with non-void operations and a return value is required. Such return value will be sent as message payload to the reply-channel specified by this Gateway.

<int-jmx:operation-invoking-outbound-gateway request-channel="requestChannel"
   reply-channel="replyChannel"
   object-name="o.s.i.jmx.config:type=TestBean,name=testBeanGateway"
   operation-name="testWithReturn"/>

If the reply-channel attribute is not provided, the reply message will be sent to the channel that is identified by the IntegrationMessageHeaderAccessor.REPLY_CHANNEL header. That header is typically auto-created by the entry point into a message flow, such as any Gateway component. However, if the message flow was started by manually creating a Spring Integration Message and sending it directly to a Channel, then you must specify the message header explicitly or use the provided reply-channel attribute.

8.1.7 MBean Exporter

Spring Integration components themselves may be exposed as MBeans when the IntegrationMBeanExporter is configured. To create an instance of the IntegrationMBeanExporter, define a bean and provide a reference to an MBeanServer and a domain name (if desired). The domain can be left out, in which case the default domain is org.springframework.integration.

<int-jmx:mbean-export id="integrationMBeanExporter"
            default-domain="my.company.domain" server="mbeanServer"/>

<bean id="mbeanServer" class="org.springframework.jmx.support.MBeanServerFactoryBean">
    <property name="locateExistingServerIfPossible" value="true"/>
</bean>

Once the exporter is defined, start up your application with:

    -Dcom.sun.management.jmxremote
    -Dcom.sun.management.jmxremote.port=6969
    -Dcom.sun.management.jmxremote.ssl=false
    -Dcom.sun.management.jmxremote.authenticate=false

Then start JConsole (free with the JDK), and connect to the local process on localhost:6969 to get a look at the management endpoints exposed. (The port and client are just examples to get you started quickly, there are other JMX clients available and some offer more sophisticated features than JConsole.)

[Important]Important

The MBean exporter is orthogonal to the one provided in Spring core - it registers message channels and message handlers, but not itself. You can expose the exporter itself, and certain other components in Spring Integration, using the standard <context:mbean-export/> tag. The exporter has a some metrics attached to it, for instance a count of the number of active handlers and the number of queued messages.

It also has a useful operation, as discussed in the section called “Orderly Shutdown Managed Operation”.

Starting with Spring Integration 4.0 the @EnableIntegrationMBeanExport annotation has been introduced for convenient configuration of a default (integrationMbeanExporter) bean of type IntegrationMBeanExporter with several useful options at the @Configuration class level. For example:

@Configuration
@EnableIntegration
@EnableIntegrationMBeanExport(server = "mbeanServer", managedComponents = "input")
public class ContextConfiguration {

	@Bean
	public MBeanServerFactoryBean mbeanServer() {
		return new MBeanServerFactoryBean();
	}
}

If there is a need to provide more options, or have several IntegrationMBeanExporter beans e.g. for different MBean Servers, or to avoid conflicts with the standard Spring MBeanExporter (e.g. via @EnableMBeanExport), you can simply configure an IntegrationMBeanExporter as a generic bean.

MBean ObjectNames

All the MessageChannel, MessageHandler and MessageSource instances in the application are wrapped by the MBean exporter to provide management and monitoring features. The generated JMX object names for each component type are listed in the table below:

Table 8.1. 

Component TypeObjectName
MessageChannelo.s.i:type=MessageChannel,name=<channelName>
MessageSourceo.s.i:type=MessageSource,name=<channelName>,bean=<source>
MessageHandlero.s.i:type=MessageSource,name=<channelName>,bean=<source>

The bean attribute in the object names for sources and handlers takes one of the values in the table below:

Table 8.2. 

Bean ValueDescription
endpointThe bean name of the enclosing endpoint (e.g. <service-activator>) if there is one
anonymousAn indication that the enclosing endpoint didn't have a user-specified bean name, so the JMX name is the input channel name
internalFor well-known Spring Integration default components
handlerNone of the above: fallback to the toString() of the object being monitored (handler or source)

Custom elements can be appended to the object name by providing a reference to a Properties object in the object-name-static-properties attribute.

Also, since Spring Integration 3.0, you can use a custom ObjectNamingStrategy using the object-naming-strategy attribute. This permits greater control over the naming of the MBeans. For example, to group all Integration MBeans under an 'Integration' type. A simple custom naming strategy implementation might be:

public class Namer implements ObjectNamingStrategy {

	private final ObjectNamingStrategy realNamer = new KeyNamingStrategy();
	@Override
	public ObjectName getObjectName(Object managedBean, String beanKey) throws MalformedObjectNameException {
		String actualBeanKey = beanKey.replace("type=", "type=Integration,componentType=");
		return realNamer.getObjectName(managedBean, actualBeanKey);
	}

}

The beanKey argument is a String containing the standard object name beginning with the default-domain and including any additional static properties. This example simply moves the standard type part to componentType and sets the type to 'Integration', enabling selection of all Integration MBeans in one query: "my.domain:type=Integration,*. This also groups the beans under one tree entry under the domain in tools like VisualVM.

[Note]Note
The default naming strategy is a MetadataNamingStrategy. The exporter propagates the default-domain to that object to allow it to generate a fallback object name if parsing of the bean key fails. If your custom naming strategy is a MetadataNamingStrategy (or subclass), the exporter will not propagate the default-domain; you will need to configure it on your strategy bean.

MessageChannel MBean Features

Message channels report metrics according to their concrete type. If you are looking at a DirectChannel, you will see statistics for the send operation. If it is a QueueChannel, you will also see statistics for the receive operation, as well as the count of messages that are currently buffered by this QueueChannel. In both cases there are some metrics that are simple counters (message count and error count), and some that are estimates of averages of interesting quantities. The algorithms used to calculate these estimates are described briefly in the table below:

Table 8.3. 

Metric TypeExampleAlgorithm
CountSend CountSimple incrementer. Increase by one when an event occurs.
DurationSend Duration (method execution time in milliseconds) Exponential Moving Average with decay factor 10. Average of the method execution time over roughly the last 10 measurements.
RateSend Rate (number of operations per second)Inverse of Exponential Moving Average of the interval between events with decay in time (lapsing over 60 seconds) and per measurement (last 10 events).
RatioSend Error Ratio (ratio of errors to total sends)Estimate the success ratio as the Exponential Moving Average of the series composed of values 1 for success and 0 for failure (decaying as per the rate measurement over time and events). Error ratio is 1 - success ratio.

A feature of the time-based average estimates is that they decay with time if no new measurements arrive. To help interpret the behaviour over time, the time (in seconds) since the last measurement is also exposed as a metric.

There are two basic exponential models: decay per measurement (appropriate for duration and anything where the number of measurements is part of the metric), and decay per time unit (more suitable for rate measurements where the time in between measurements is part of the metric). Both models depend on the fact that

S(n) = sum(i=0,i=n) w(i) x(i)

has a special form when w(i) = r^i, with r=constant:

S(n) = x(n) + r S(n-1)

(so you only have to store S(n-1), not the whole series x(i), to generate a new metric estimate from the last measurement). The algorithms used in the duration metrics use r=exp(-1/M) with M=10. The net effect is that the estimate S(n) is more heavily weighted to recent measurements and is composed roughly of the last M measurements. So M is the "window" or lapse rate of the estimate In the case of the vanilla moving average, i is a counter over the number of measurements. In the case of the rate we interpret i as the elapsed time, or a combination of elapsed time and a counter (so the metric estimate contains contributions roughly from the last M measurements and the last T seconds).

Orderly Shutdown Managed Operation

The MBean exporter provides a JMX operation to shut down the application in an orderly manner, intended for use before terminating the JVM.

public void stopActiveComponents(boolean force, long howLong)

Its use and operation are described in Section 8.6, “Orderly Shutdown”.

8.2 Message History

The key benefit of a messaging architecture is loose coupling where participating components do not maintain any awareness about one another. This fact alone makes your application extremely flexible, allowing you to change components without affecting the rest of the flow, change messaging routes,   message consuming styles (polling vs event driven), and so on. However, this unassuming style of architecture could prove to be difficult when things go wrong. When debugging, you would probably like to get as much information about the message as you can (its origin, channels it has traversed, etc.)

Message History is one of those patterns that helps by giving you an option to maintain some level of awareness of a message path either for debugging purposes or to maintain an audit trail. Spring integration provides a simple way to configure your message flows to maintain the Message History by adding a header to the Message and updating that header every time a message passes through a tracked component.

8.2.1 Message History Configuration

To enable Message History all you need is to define the message-history element in your configuration.

<int:message-history/>

Now every named component (component that has an 'id' defined) will be tracked. The framework will set the 'history' header in your Message. Its value is very simple - List<Properties>.

<int:gateway id="sampleGateway" 
    service-interface="org.springframework.integration.history.sample.SampleGateway"
    default-request-channel="bridgeInChannel"/>

<int:chain id="sampleChain" input-channel="chainChannel" output-channel="filterChannel">
  <int:header-enricher>
    <int:header name="baz" value="baz"/>
  </int:header-enricher>
</int:chain>

The above configuration will produce a very simple Message History structure:

[{name=sampleGateway, type=gateway, timestamp=1283281668091},
 {name=sampleChain, type=chain, timestamp=1283281668094}]

To get access to Message History all you need is access the MessageHistory header. For example:

Iterator<Properties> historyIterator =
    message.getHeaders().get(MessageHistory.HEADER_NAME, MessageHistory.class).iterator();
assertTrue(historyIterator.hasNext());
Properties gatewayHistory = historyIterator.next();
assertEquals("sampleGateway", gatewayHistory.get("name"));
assertTrue(historyIterator.hasNext());
Properties chainHistory = historyIterator.next();
assertEquals("sampleChain", chainHistory.get("name"));

You might not want to track all of the components. To limit the history to certain components based on their names, all you need is provide the tracked-components attribute and specify a comma-delimited list of component names and/or patterns that match the components you want to track.

<int:message-history tracked-components="*Gateway, sample*, foo"/>

In the above example, Message History will only be maintained for all of the components that end with 'Gateway', start with 'sample', or match the name 'foo' exactly.

Starting with version 4.0, you can also use the @EnableMessageHistory annotation in a @Configuration class. In addition, the MessageHistoryConfigurer bean is now exposed as a JMX MBean by the IntegrationMBeanExporter (see Section 8.1.7, “MBean Exporter”), allowing the patterns to be changed at runtime. Note, however, that the bean must be stopped (turning off message history) in order to change the patterns. This feature might be useful to temporarily turn on history to analyze a system. The MBean's object name is "<domain>:name=messageHistoryConfigurer,type=MessageHistoryConfigurer".

[Important]Important
If multiple beans (declared by @EnableMessageHistory and/or <message-history/>) they all must have identical component name patterns (when trimmed and sorted). Do not use a generic <bean/> definition for the MessageHistoryConfigurer.
[Note]Note
Remember that by definition the Message History header is immutable (you can't re-write history, although some try). Therefore, when writing Message History values, the components are either creating brand new Messages (when the component is an origin), or they are copying the history from a request Message, modifying it and setting the new list on a reply Message. In either case, the values can be appended even if the Message itself is crossing thread boundaries. That means that the history values can greatly simplify debugging in an asynchronous message flow.

8.3 Message Store

Enterprise Integration Patterns (EIP) identifies several patterns that have the capability to buffer messages. For example, an Aggregator buffers messages until they can be released and a QueueChannel buffers messages until consumers explicitly receive those messages from that channel. Because of the failures that can occur at any point within your message flow, EIP components that buffer messages also introduce a point where messages could be lost.

To mitigate the risk of losing Messages, EIP defines the Message Store pattern which allows EIP components to store Messages typically in some type of persistent store (e.g. RDBMS).

Spring Integration provides support for the Message Store pattern by a) defining a org.springframework.integration.store.MessageStore strategy interface, b) providing several implementations of this interface, and c) exposing a message-store attribute on all components that have the capability to buffer messages so that you can inject any instance that implements the MessageStore interface.

Details on how to configure a specific Message Store implementation and/or how to inject a MessageStore implementation into a specific buffering component are described throughout the manual (see the specific component, such as QueueChannel, Aggregator, Resequencer etc.), but here are a couple of samples to give you an idea:

QueueChannel

<int:channel id="myQueueChannel">
    <int:queue message-store="refToMessageStore"/>
<int:channel>

Aggregator

<int:aggregator  message-store="refToMessageStore"/>

By default Messages are stored in-memory using org.springframework.integration.store.SimpleMessageStore, an implementation of MessageStore. That might be fine for development or simple low-volume environments where the potential loss of non-persistent messages is not a concern. However, the typical production application will need a more robust option, not only to mitigate the risk of message loss but also to avoid potential out-of-memory errors. Therefore, we also provide MessageStore implementations for a variety of data-stores. Below is a complete list of supported implementations:

[Important]Important

However be aware of some limitations while using persistent implementations of the MessageStore.

The Message data (payload and headers) is serialized and deserialized using different serialization strategies depending on the implementation of the MessageStore. For example, when using JdbcMessageStore, only Serializable data is persisted by default. In this case non-Serializable headers are removed before serialization occurs. Also be aware of the protocol specific headers that are injected by transport adapters (e.g., FTP, HTTP, JMS etc.). For example, <http:inbound-channel-adapter/> maps HTTP-headers into Message Headers and one of them is an ArrayList of non-Serializable org.springframework.http.MediaType instances. However you are able to inject your own implementation of the Serializer and/or Deserializer strategy interfaces into some MessageStore implementations (such as JdbcMessageStore) to change the behaviour of serialization and deserialization.

Special attention must be paid to the headers that represent certain types of data. For example, if one of the headers contains an instance of some Spring Bean, upon deserialization you may end up with a different instance of that bean, which directly affects some of the implicit headers created by the framework (e.g., REPLY_CHANNEL or ERROR_CHANNEL). Currently they are not serializable, but even if they were, the deserialized channel would not represent the expected instance.

Beginning with Spring Integration version 3.0, this issue can be resolved with a header enricher, configured to replace these headers with a name after registering the channel with the HeaderChannelRegistry.

Also when configuring a message-flow like this: gateway -> queue-channel (backed by a persistent Message Store) -> service-activator That gateway creates a Temporary Reply Channel, and it will be lost by the time the service-activator's poller reads from the queue. Again, you can use the header enricher to replace the headers with a String representation.

For more information, refer to the Section 6.2.2, “Header Enricher”.

Spring Integration 4.0 introduced two new interfaces ChannelMessageStore - to implement operations specific for QueueChannels, PriorityCapableChannelMessageStore - to mark MessageStore implementation to be used for PriorityChannels and to provide priority order for persisted Messages. The real behaviour depends on implementation. The Framework provides these implementations, which can be used as a persistent MessageStore for PriorityChannel:

[Caution]Caution with SimpleMessageStore

Starting with version 4.1, the SimpleMessageStore no longer copies the message group when calling getMessageGroup(). For large message groups, this was a significant performance problem. 4.0.1 introduced a boolean copyOnGet allowing this to be controlled. When used internally by the aggregator, this was set to false to improve performance. It is now false by default.

Users accessing the group store outside of components such as aggregators, will now get a direct reference to the group being used by the aggregator, instead of a copy. Manipulation of the group outside of the aggregator may cause unpredictable results.

For this reason, users should not perform such manipulation, or set the copyOnGet property to true.

8.4 Metadata Store

Many external systems, services or resources aren't transactional (Twitter, RSS, file system etc.) and there is no any ability to mark the data as read. Or there is just need to implement the Enterprise Integration Pattern Idempotent Receiver in some integration solutions. To achieve this goal and store some previous state of the Endpoint before the next interaction with external system, or deal with the next Message, Spring Integration provides the Metadata Store component being an implementation of the org.springframework.integration.metadata.MetadataStore interface with a general key-value contract.

The Metadata Store is designed to store various types of generic meta-data (e.g., published date of the last feed entry that has been processed) to help components such as the Feed adapter deal with duplicates. If a component is not directly provided with a reference to a MetadataStore, the algorithm for locating a metadata store is as follows: First, look for a bean with id metadataStore in the ApplicationContext. If one is found then it will be used, otherwise it will create a new instance of SimpleMetadataStore which is an in-memory implementation that will only persist metadata within the lifecycle of the currently running Application Context. This means that upon restart you may end up with duplicate entries.

If you need to persist metadata between Application Context restarts, two persistent MetadataStores are provided by the framework:

The PropertiesPersistingMetadataStore is backed by a properties file and a PropertiesPersister.

<bean id="metadataStore"
    class="org.springframework.integration.store.PropertiesPersistingMetadataStore"/>

Alternatively, you can provide your own implementation of the MetadataStore interface (e.g. JdbcMetadataStore) and configure it as a bean in the Application Context.

Starting with version 4.0, SimpleMetadataStore, PropertiesPersistingMetadataStore and RedisMetadataStore implement ConcurrentMetadataStore. These provide for atomic updates and can be used across multiple component or application instances.

8.4.1 Idempotent Receiver and Metadata Store

The Metadata Store is useful for implementing the EIP Idempotent Receiver pattern, when there is need to filter an incoming Message if it has already been processed, and just discard it or perform some other logic on discarding. The following configuration is an example of how to do this:

<int:filter input-channel="serviceChannel"
			output-channel="idempotentServiceChannel"
			discard-channel="discardChannel"
			expression="@metadataStore.get(headers.businessKey) == null"/>

<int:publish-subscribe-channel id="idempotentServiceChannel"/>

<int:outbound-channel-adapter channel="idempotentServiceChannel"
                              expression="@metadataStore.put(headers.businessKey, '')"/>

<int:service-activator input-channel="idempotentServiceChannel" ref="service"/>

The value of the idempotent entry may be some expiration date, after which that entry should be removed from Metadata Store by some scheduled reaper.

Also see Section 7.7.7, “Idempotent Receiver Enterprise Integration Pattern”.

8.5 Control Bus

As described in (EIP), the idea behind the Control Bus is that the same messaging system can be used for monitoring and managing the components within the framework as is used for "application-level" messaging. In Spring Integration we build upon the adapters described above so that it's possible to send Messages as a means of invoking exposed operations.

<int:control-bus input-channel="operationChannel"/>

The Control Bus has an input channel that can be accessed for invoking operations on the beans in the application context. It also has all the common properties of a service activating endpoint, e.g. you can specify an output channel if the result of the operation has a return value that you want to send on to a downstream channel.

The Control Bus executes messages on the input channel as Spring Expression Language expressions. It takes a message, compiles the body to an expression, adds some context, and then executes it. The default context supports any method that has been annotated with @ManagedAttribute or @ManagedOperation. It also supports the methods on Spring's Lifecycle interface, and it supports methods that are used to configure several of Spring's TaskExecutor and TaskScheduler implementations. The simplest way to ensure that your own methods are available to the Control Bus is to use the @ManagedAttribute and/or @ManagedOperation annotations. Since those are also used for exposing methods to a JMX MBean registry, it's a convenient by-product (often the same types of operations you want to expose to the Control Bus would be reasonable for exposing via JMS). Resolution of any particular instance within the application context is achieved in the typical SpEL syntax. Simply provide the bean name with the SpEL prefix for beans (@). For example, to execute a method on a Spring Bean a client could send a message to the operation channel as follows:

Message operation = MessageBuilder.withPayload("@myServiceBean.shutdown()").build();
operationChannel.send(operation)

The root of the context for the expression is the Message itself, so you also have access to the 'payload' and 'headers' as variables within your expression. This is consistent with all the other expression support in Spring Integration endpoints.

8.6 Orderly Shutdown

As described in Section 8.1.7, “MBean Exporter”, the MBean exporter provides a JMX operation stopActiveComponents, which is used to stop the application in an orderly manner. The operation has a single long parameter. The parameter indicates how long (in milliseconds) the operation will wait to allow in-flight messages to complete. The operation works as follows:

The first step calls beforeShutdown() on all beans that implement OrderlyShutdownCapable. This allows such components to prepare for shutdown. Examples of components that implement this interface, and what they do with this call include: JMS and AMQP message-driven adapters stop their listener containers; TCP server connection factories stop accepting new connections (while keeping existing connections open); TCP inbound endpoints drop (log) any new messages received; http inbound endpoints return 503 - Service Unavailable for any new requests.

The second step stops any active channels, such as JMS- or AMQP-backed channels.

The third step stops all MessageSources.

The fourth step stops all inbound MessageProducers (that are not OrderlyShutdownCapable).

The fifth step waits for any remaining time left, as defined by the value of the long parameter passed in to the operation. This is intended to allow any in-flight messages to complete their journeys. It is therefore important to select an appropriate timeout when invoking this operation.

The sixth step calls afterShutdown() on all OrderlyShutdownCapable components. This allows such components to perform final shutdown tasks (closing all open sockets, for example).

As discussed in the section called “Orderly Shutdown Managed Operation” this operation can be invoked using JMX. If you wish to programmatically invoke the method, you will need to inject, or otherwise get a reference to, the IntegrationMBeanExporter. If no id attribute is provided on the <int-jmx:mbean-export/> definition, the bean will have a generated name. This name contains a random component to avoid ObjectName collisions if multiple Spring Integration contexts exist in the same JVM (MBeanServer).

For this reason, if you wish to invoke the method programmatically, it is recommended that you provide the exporter with an id attribute so it can easily be accessed in the application context.

Finally, the operation can be invoked using the <control-bus>; see the monitoring Spring Integration sample application for details.

[Important]Important
The above algorithm was improved in version 4.1. Previously, all task executors and schedulers were stopped. This could cause mid-flow messages in QueueChannels to remain. Now, the shutdown leaves pollers running in order to allow these messages to be drained and processed.