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Copyright 2005-2010 SpringSource. Copying, publishing or distributing without express written permission is prohibit

Message Driven

Architecture with Spring

Mark Fisher, SpringSource/VMware

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2Copyright 2005-2010 SpringSource. Copying, publishing or distributing without express written permission is prohibit

Agenda

Events Messaging

Polling

Scheduling

Pipes and Filters

Enterprise Integration Patterns

Q&A

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Events

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Sending ApplicationEvents

publicclass MyEventPublisher implements ApplicationEventPublisherAware { privatevolatile ApplicationEventPublisher publisher; publicvoid setApplicationEventPublisher(ApplicationEventPublisher aep) { this.publisher = aep;

}

publicvoid send(String text) {Assert.notNull(this.publisher, no publisher available); this.publisher.publishEvent(new MyEvent(text));

}

}

1. Implement the callback to have the publisher injected by the container.

2. Define the bean, and use the publisher to send events at runtime.

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Receiving ApplicationEvents

publicclass MyEventListener implements ApplicationListener {privatefinal Log log = LogFactory.getLog(this.getClass());publicvoid onApplicationEvent(ApplicationEvent event) {this.log.info("received event: " + event);}

}

1. Implement the ApplicationListener interface.

2. Define the bean, and it will be invoked at runtime when Events occur.

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Filtering Event Types

publicclass FooEventListener implements ApplicationListener {privatefinal Log log = LogFactory.getLog(this.getClass());publicvoid onApplicationEvent(FooEvent event) {this.log.info("received FOO event: " + event);}

}

1. Implement the ApplicationListener interface with a parameterized type.

2. Define the bean, and it will be invoked at runtime when that type of Event occurs.

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7/43Copyright 2005-2010 SpringSource. Copying, publishing or distributing without express written permission is prohibit

Messaging

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Sending JMS Messages

publicclass MessageSender { @Autowiredprivate volatile JmsTemplate jmsTemplate;

publicvoid send(String message) { this.jmsTemplate.convertAndSend("example.queue", message);}}

1. Inject an instance of Spring's JmsTemplate.

2. Provide the JMS ConnectionFactory in the JmsTemplate bean definition.

...

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Receiving JMS Messages

publicclass MyListener {privatefinal Log log = LogFactory.getLog(this.getClass());

publicvoid log(String message) { this.log.info("received: " + message);}}

1. Define a listener-container within the context.

2. Point to any POJO to implicitly create a MessageListenerAdapter.

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Spring AMQP

Similar to Spring's JMS support Does not hide AMQP behind JMS

Currently in 1.0 milestone phase

Exchanges Where producers send Messages May also send a routing key

Queues Where consumers receive Messages A named FIFO buffer

Bindings Exchanges route to queues Queues bind with routing keys/patterns

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Sending and ReceivingAMQP Messages

publicclass MessageSender { @Autowiredprivate volatile AmqpTemplate amqpTemplate;

publicvoid send(String message) { this.amqpTemplate.convertAndSend( "myExchange", "some.routing.key", message);}}

1. Use AmqpTemplate instead of JmsTemplate (accepts exchange and routingKey).

2. Nothing changes on the listener side (just a POJO).

publicclass MyListener {privatefinal Log log = LogFactory.getLog(this.getClass());

publicvoid log(String message) { this.log.info("received: " + message);}}

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Polling

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Lifecycle Management

publicinterface Lifecycle {void start();void stop();boolean isRunning();}

Spring's Lifecycle interface provides basic support for any background task.

publicinterface SmartLifecycle extends Lifecycle, Phased {boolean isAutoStartup();void stop(Runnable callback);}

publicinterface Phased {int getPhase();}

SmartLifecycle adds auto-startup and graceful shutdown capabilities.

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Task Execution

publicclass FilePoller implements Lifecycle { @Autowired @Qualifier("threadPool")private volatile Executor executor; publicvoid start() { this.executor.execute(new Runnable() { publicvoid run() { while (!this.stopRequested) { // poll a directory by calling listFiles()

// send the list of Files to a handler }}});}...

Spring provides a TaskExecutor whose signature matches Executor.

Several implementations are available: Threads can be managed, pooled, etc.

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@Async

publicclass FilePoller implements Lifecycle { @Async publicvoid start() { while (!this.stopRequested) { // poll a directory by calling listFiles()// send the list of Files to a handler }}...}

The @Async annotation implicitly adds the Executor support.

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Scheduling

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Task Scheduler and Trigger

publicinterface TaskScheduler {ScheduledFuture schedule(Runnable task, Trigger trigger);ScheduledFuture scheduleAtFixedRate(Runnable task, long period);ScheduledFuture scheduleWithFixedDelay(Runnable task, long delay);...}

Spring's TaskScheduler and Trigger provide an abstraction for scheduling tasks.

publicinterface Trigger {Date nextExecutionTime(TriggerContext triggerContext);

} publicinterface TriggerContext {Date lastScheduledExecutionTime();Date lastActualExecutionTime();Date lastCompletionTime()}

Trigger implementations include: PeriodicTrigger CronTrigger

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Task Scheduling

publicclass FilePoller implements Lifecycle { @Autowired @Qualifier("scheduler")private volatile TaskScheduler scheduler; // other properties, e.g. 'task' and 'trigger' publicvoid start() { this.task = this.scheduler.schedule(task, trigger);} publicvoid stop() { if (this.task != null ) { this.task.cancel(true); }}...}

TaskScheduler supports recurring, cancelable tasks.

As with TaskExecutor, Threads can be managed, pooled, etc.

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@Scheduled

publicclass FilePoller { @Scheduled(cron="*/5 * 9-17 * * ?") publicvoid poll() { // poll and send Files to a handler}}

The @Scheduled annotation implicitly adds the TaskScheduler support.

Spring also provides as an alternative to annotations.

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@Scheduled as Meta-annotation

@Scheduled(cron="${schedules.daytime}")@Target(ElementType.METHOD)@Retention(RetentionPolicy.RUNTIME)public@interface Daytime {} @Daytime publicvoid poll() { // poll and send Files to a handler}

schedules.daytime=*/5 * 9-17 * * ?

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Pipes and Filters

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Message

Payload can be any object

Header values are stored in a Map

Headers

Payload

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Message and Headers

public interface Message {

MessageHeaders getHeaders();

T getPayload();

}

public interface Message {

MessageHeaders getHeaders();

T getPayload();

}

Message m1 = MessageBuilder.withPayload(foo).setHeader(itemId, 123).build();

Message m2 = MessageBuilder.fromMessage(m1).setHeader(itemId, 456).build();

Message m1 = MessageBuilder.withPayload(foo).setHeader(itemId, 123).build();

Message m2 = MessageBuilder.fromMessage(m1).setHeader(itemId, 456).build();

MessageHeaders headers = message.getHeaders();

long timestamp = headers.getTimestamp();

String value = headers.get(someKey, String.class);

MessageHeaders headers = message.getHeaders();

long timestamp = headers.getTimestamp();

String value = headers.get(someKey, String.class);

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Message Channel

Decouples Producers from Consumers

Provides extension point for interceptors

May be Point-to-Point

Or Publish/Subscribe

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Message Channel Types

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Sending Messages

public interface MessageChannel { boolean send(Message message); boolean send(Message message, long timeout);}

public interfaceMessageChannel { boolean send(Message message); boolean send(Message message, long timeout);} MessagingTemplate template = new MessagingTemplate();

template.send(someChannel, message);

template.send(fooChannel, message);

template.convertAndSend(someChannel, hello);

template.convertAndSend(fooChannel, someObject);

template.setSendTimeout(5000);

template.setDefaultChannel(someChannel);

template.convertAndSend(someObject);

MessagingTemplate template = new MessagingTemplate();template.send(someChannel, message);

template.send(fooChannel, message);

template.convertAndSend(someChannel, hello);

template.convertAndSend(fooChannel, someObject);

template.setSendTimeout(5000);

template.setDefaultChannel(someChannel);

template.convertAndSend(someObject);

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Gateway Proxy

public interface MyGateway { void send(String text);

String send(@Payload Foo foo, @Header(bar) String s);

}

public interfaceMyGateway { void send(String text);

String send(@Payload Foo foo, @Header(bar) String s);

}

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Message Publishing Interceptor

Non-invasive, AOP-based implementation

Uses SpEL for generating payload and headers

@Publisher(channel="confirmations") // payload = #return

public String createBooking(BookingRequest request) {...

}

@Publisher(payload="#args.bookingId", channel="cancellations")public void cancelBooking(String bookingId) {

...}

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@Publisher as a Meta-Annotation

@Publisher(channel="auditChannel")public @interface Audit {}

Define a custom annotation

Apply to methods, no channel required

@Auditpublic UsercreateUser(String name) {...}

@Auditpublic UserdeleteUser(long userId) {...}

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Receiving Messages

Inversion of Control Endpoints delegate to Spring-managed objects

Framework handles message reception andmethod invocation

Similar but more abstract than Spring JMS

Clean separation of Code and Configuration

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Message Endpoint

Producers send Messages to a MessageChannel

Depending on their type, Message Channelsmay have Polling Consumers

Or Event-Driven Consumers

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Enterprise IntegrationPatterns

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Message Endpoint Types

Transformer Convert payload or modify headers

Filter

Discard messages based on boolean evaluation

Router

Determine next channel based on content

Splitter

Generate multiple messages from one Aggregator

Assemble a single message from multiple

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Expression Language Support

Alternative option for ref/method in endpoints

Mapping between Messages and Methods

public void createAccount(

@Payload("firstName") String firstName,@Payload("lastName") String lastName,@Header("userInfo.account.id") String accountId) {...}

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Groovy Support

Another option for endpoints

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Channel Adapters andMessaging Gateways

JMS

AMQP

TCP

UDP

File/FTP/SFTP

RMI

RSS

HTTP (REST)

WS (SOAP/POX)

Mail (POP3/IMAP/SMTP)

JDBC

XMPP

Twitter

Spring Events

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Channel Adapters (one-way)
http://inbound-channel-adapter/http://inbound-channel-adapter/

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Gateways (request-reply)

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XML Support

XPath Router XPath Splitter

XPath Transformer

XPath Header Enricher XSLT Transformer

OXM Marshalling Transformer

OXM Unmarshalling Transformer

Spring Integration and

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Spring Integration andOther Spring Projects

Spring Integration for .NET Spring AMQP: Channel Adapters

Spring BlazeDS (Flex): Messaging Adapter

Spring Batch: Jobs Events Spring Web Services: Gateways

Spring Security: Channel Interceptor

Spring Roo: Addon SpringSource Tool Suite

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STS Visual Editor

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Demos

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Links

Spring Framework Documentation http://static.springsource.org/spring/docs/3.0.x

Spring AMQP

http://www.springsource.org/spring-amqp

Spring Integration http://www.springsource.org/spring-integration

Enterprise Integration Patterns

http://enterpriseintegrationpatterns.com

Sample Code http://git.springsource.org/spring-integration/samples

mda with spring 11-18-10

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