first given at Confoo.ca

1. Elegant Systems Integration
with Apache Camel
Pradeep Elankumaran
Intridea, Inc.
pradeep@intridea.com
@pradeep24

2. About Us
❖ Intridea is a high-end web consulting shop
❖ Based out of Washington DC, but dispersed all over the
United States
❖ Our most popular product is Presently, an enterprise
microblogging platform
❖ Specialize in development using Ruby, Rails, Java, Erlang
and beyond

3. What’s the Problem?
❖ Most web applications require a suite of supporting services
❖ ex: email queue, RSS import, notification emails, etc.
❖ Many great libraries, but hard to identify best-of-breed
❖ Effort required to stitch together custom supporting
services and backends for every new site

4. What is Apache Camel?
(marketing-speak)
❖ Message-Oriented Middleware
❖ Rule-based message routing
❖ Message mediation engine
❖ Apache 2 License

5. What is Apache Camel?
(plain-speak)
❖ a Routing Engine
❖ Provides you pluggable Components ex: JMS, RSS, SMTP, IMAP, XMPP
❖ Can define chains of components, allowing messages to flow
from one component to another - routes.
❖ Can convert messages from one format to another within
these routes
❖ Very extensible - can add your own app-specific components
❖ Very fast & lean

6. A Few Code Examples

7. A Basic Camel Route
from the ‘EmailQueue’ ActiveMQ queue
from(“active-mq:queue:/EmailQueue”).
to(“smtp://user@smtp.intridea.com?
password=mypassword&to=pradeep@intridea.com”)
deliver directly to pradeep@intridea.com via SMTP

8. A Bit More Advanced...
throttle the queue
to 10 XMPP stanzas
every 20 seconds
from(“active-mq:queue:/XMPPQueue”). converts JSON from the
throttle(10).timePeriodMillis(20000). queue to a XMPP message
unmarshal().json(JsonLibrary.JACKSON). using the Jackson JSON
library
to(“xmpp://pradeep@jabber.org/?
room=krypton@conference.jabber.org&password=secret”)
send every message to the ‘krypton’
chat room via XMPP on the
jabber.org server

9. A Long-Running Route
from the reddit.com RSS feed
from(“rss:http://reddit.com/.rss?splitEntries=true”).
marshal().rss().
filter().xpath(“//item/title[contains(., ‘Montreal’)]”).
process(new MyCustomRSSProcessor()).
to(“mina:tcp://mywebapp.com/postToApp”)
run matched messages through a
filter messages by XPath custom processor that converts to
your special data format
POSTs final message to this URL

10. Camel is Powerful.

11. Component List
ActiveMQ Freemarker JPA RMI StringTemplate
AMQP FTP JT/400 RNC TCP
Atom GHttp LDAP RNG Test
Bean GTask Log RSS Timer
Browse GMail Mail SEDA UDP
Cache Hibernate MINA SERVLET Validation
Cometd HL7 Mock SFTP Velocity
CXF HTTP MSV Smooks VM
CXFRS IMAP Multicast SMTP XMPP
DataSet IRC NMR SNMP XQuery
Direct JavaSpace POP Spring XSLT
Esper JBI Printer SQL
Event JCR Quartz Stream
File JDBC Quickfix
Flatpack Jetty Ref
JMS Restlet

12. Can hook up most of these
components with each other.

13. Camel allows you to be
data-format agnostic

14. Can add new, custom
components very easily

15. Camel integrates with Spring
using an XML/POJO based Spring DSL

16. Robust Error-Handling DSL
errorHandler(defaultErrorHandler().
maximumRedeliveries(2).
backOffMultiplier(2).
retryAttemptedLogLevel(LoggingLevel.WARN));
onException(IOException.class).
maximumRedeliveries(3).
redeliverDelay(1000);

17. A Real-World Case Study
Present.ly

18. What is Present.ly?
❖ Enterprise Micro-blogging platform
❖ Written in Ruby on Rails
❖ A pretty big XMPP component for message delivery
❖ Requires a lot of supporting architecture/daemons

19. Pre-Camel Architecture
Rails eJabberd (XMPP)
Notifs Processor
Email Sender
Queue RUBY Daily Digests
IMAP Processor
IM Gateway
multiple ruby daemons we had to manage

20. Present.ly w/ Camel
eJabberd (XMPP)
Rails Notifs Processor
STOMP protocol Email Sender
ActiveMQ Camel JAVA Daily Digests
IMAP Processor
IM Gateway
one easy-to-deploy .jar file,
can easily interface with Feed Fetcher
different architectures

21. Easy to setup
Shared-Nothing
app instances

22. Camel in Detail

23. All Camel code runs inside a
CamelContext
Type
Components Converters
Endpoints CamelContext Data Formats
Routes Languages

24. Most of the components are
backed by stable, best-of-
breed Java libraries

25. Processing and Filtering
messages is very easy

26. One Final Example
import org.apache.activemq.camel.component.ActiveMQComponent;
import org.apache.camel.CamelContext;
import org.apache.camel.Exchange;
import org.apache.camel.Processor;
import org.apache.camel.builder.RouteBuilder;
import org.apache.camel.impl.DefaultCamelContext;
public class MyCamelRouter {
public static void main(String args[]) throws Exception {
// initialize a new CamelContext
CamelContext context = new DefaultCamelContext();
// attach the ActiveMQ component
context.addComponent("active-mq",
ActiveMQComponent.activeMQComponent("tcp://localhost:81816"));
context.addRoutes(new RouteBuilder(){
public void configure() {
// setup a new route
from("active-mq:queue:/MyRandomQueue").
throttle(5).timePeriodMillis(10000).
process(new Processor() {
public void process(Exchange exchange) {
System.out.println("RECV: "+exchange.getIn().getBody(String.class));
}
}).to("mina:tcp://mywebsite.com/");
}
});
}
}

27. Learn more...

28. Enterprise Integration
Patterns (EIP)
❖ Many recipes for common integration issues
❖ Excellent book by Gregor Hohpe and Bobby Woolf
❖ Camel formalizes the language for a very big subset of the
patterns listed in this book
❖ Leverage the patterns to create scalable architectures for
your application using the tools Camel gives you.

29. Examples of EIP Patterns

30. Examples of EIP Patterns

31. Learning More Camel
❖ Website is very comprehensive
❖ Downloadable Manual
❖ Mailing lists are handy
❖ Email me! pradeep@intridea.com
❖ Camel in Action by Claus Ibsen, Jonathan Anstey & Hadrian Zbarcea

32. Questions?
Reach me at
pradeep@intridea.com
@pradeep24

33. Something new...

34. Llama
❖ A port of Camel to Ruby
❖ based off EventMachine, so it runs ROCK SOLID
❖ early alpha at this point, looking for helpers
❖ github.com/skyfallsin/llama

35. Llama Code Example

36. github.com/skyfallsin/llama