Enterprise Integration Patterns and their implementation using Apache Camel. A talk given as part of Waterford Tech. Meetup on 26th of September 2018.

1. Enterprise Integration Patterns
&
Apache Camel
Milos Zubal
Waterford Tech. Meetup 26.09.2018

2. Who’s this?!
@MilosZubal
Software Engineer at
(we’re hiring! ;) )
11+ years of backend Java happiness
https://www.linkedin.com/in/miloszubal/
https://github.com/mzubal
https://twitter.com/MilosZubal
(if you think the accent is very strange I am
from Czech Republic :) )

3. What are you
going to hear
today?
● Enterprise Integration Patterns
(EIPs)
● Apache Camel

4. Some of the challenges of application integration
● Spaghetti integration (point-to-point)
● Unreliable/slow transport medium
● Many different data formats
● Performance/Throughput
● On-going change

5. Integrate apps? Why?
● Real-time data integration
● Process automation
● Improved flexibility
● “WTF? We do microservices!”
There is a fancy urban legend of a company where “Orders” department printed (physically!) all the
new customer details every week and passed that to the “Accounting” department so they can manually
type all the info into their system.

6. Integrate apps? How?
● File Transfer
● Shared DB
● RPC
● Messages

7. File Transfer
● Pros
○ Location decoupling
○ Temporal decoupling
○ Language agnostic
○ Works everywhere
● Cons
○ Delay in transfer
○ Large amount of data
○ Write/Read at the same time

8. Shared DB
● Pros
○ Consistency/Transactions
○ Reporting
● Cons
○ Purely data integration
○ No Process integration
○ No isolation
○ Performance/Locking

9. RPC
● Pros
○ Integration on demand
○ Also Process/Function integration
● Cons
○ Easily evolves into spaghetti
○ Tight coupling (location, temporal)
○ Performance problems (the call is
blocking resources)

10. Messaging (Async)
● Pros
○ Any type of integration
○ Decoupling (location/temporal)
○ Performance/Throttling
○ “Honest” approach to model the communication
● Cons
○ It is a different programming model
○ Usually need for a Message Broker

11. We have just covered Integration Styles of EIP

12. Enterprise Integration Patterns (EIPs)
● EIPs == GoF of application integration
● Set of 65 patterns to describe/design scalable
and maintainable integration solutions
● Published 10.10.2003
● 700 pages
● Authors: Gregor Hohpe
/ Bobby Woolf

13. Enterprise Integration Patterns
● Model integration as asynchronous messages
● Focus mainly on the communication of the apps and their edge
components
● Focus on stateless communication
● Usually one-way communication (not Request-Reply)
● Assumes using Message Broker to deliver messages (but there
are some architectures without MB)
● “Wider bridges, not faster cars.”
● Please make sure you don’t fall into the trap of applying integration
patterns to everything! (Keep things simple!)

14. Main EIP groups
Channel Patterns
(how to transport the Message)
Message Patterns
(how to design the Message)
Routing Patterns
(how to route the Message to its destination)
Transformation Patterns
(how to transform the Message to needed format)
Endpoint Patterns
(how to produce/consume the Message with
non-messaging systems)
Management Patterns
(how to monitor, test and manage the system

15. EIP Game: Guess the Pattern Name!
“Use a Splitter to break out the composite message into
a series of individual messages, each containing data
related to one item.”
????

16. EIP Game: Guess the Pattern Name!
????
“Use a stateful filter, an Aggregator, to collect and store
individual messages until a complete set of related messages
has been received. Then, the Aggregator publishes a single
message distilled from the individual messages.”

17. EIP Game: Guess the Pattern Name!
????
“Insert a special filter, a Message Router, which consumes a
Message from one Message Channel and republishes it to a
different Message Channel channel depending on a set of
conditions.”

18. Claim Check

19. The are a lot more EIPs
● All of them can be combined
or composed into “higher-
level” patterns
● Just like with GoF, you might
be using some of them
already
● All of them can be found on
enterpriseintegrationpatterns.com

20. Pipes and Filters

21. Loan Broker example

22. EIPs do not focus on
● Data modelling
● Stateful
communication/processes
(conversations)
● Correct modularisation or
application boundaries
○ Check Domain Driven
Desing (DDD)

23. EIPs - key benefits
● Robust Patterns to implement scalable and maintainable
integrations
● Common vocabulary
● Simple and expressive Graphical Notation

24. Implementing EIPs
Small
(frameworks)
Apache Camel
Spring Integration
NServiceBus (.NET)
Medium
(ESBs, Brokers)
JBoss Fuse
Mule
WSO2
TIBCO
Oracle ESB
IBM WebSphere ESB
Large
(SOA Suites)
Oracle SOA Suite
Service Works
(other major vendors)

25. Apache Camel
“Apache Camel is a powerful open source integration framework based on
known Enterprise Integration Patterns with powerful bean integration.”
● Open-source implementation of EIPs
● Backed by RedHat (it is part of JBoss Fuse)
● First release - summer 2007

26. Camel: basic architecture

27. Content Based Router - the Camel way
from newOrder
choice
when isWidget to widget
otherwise to gadget

28. Content Based Router - the Camel way
from(newOrder)
choice
when(isWidget)to(widget)
otherwise to(gadget)

29. Content Based Router - the Camel way
from(newOrder)
.choice()
.when(isWidget).to(widget)
.otherwise().to(gadget);

30. Content Based Router - the Camel way
from(newOrder)
.choice()
.when(isWidget).to(widget)
.otherwise().to(gadget);
Endpoint newOrder = endpoint(“amqp:queue:newOrder”);
Predicate isWidget = xpath(“/order/product = ‘widget’”);
Endpoint widget = endpoint(“amqp:queue:widget”);
Endpoint gadget = endpoint(“amqp:queue:gadget”);

31. Content Based Router - the Camel way
public class MyRouteBuilder extends RouteBuilder {
@Override
public void configure() throws Exception {
Endpoint newOrder = endpoint(“amqp:queue:newOrder”);
Predicate isWidget = xpath(“/order/product = ‘widget’”);
Endpoint widget = endpoint(“amqp:queue:widget”);
Endpoint gadget = endpoint(“amqp:queue:gadget”);
from(newOrder)
.choice()
.when(isWidget).to(widget)
.otherwise().to(gadget);
}}

32. Content Based Router - the Camel way
public class MyRouteBuilder extends RouteBuilder {
@Override
public void configure() throws Exception {
from(“amqp:queue:newOrder”)
.choice()
.when(xpath(“/order/product=‘widget’”).to(“amqp:queue:widget”)
.otherwise().to(“amqp:queue:gadget”);
}}

33. public void configure() throws Exception {
from(“amqp:queue:newOrder”)
.choice()
.when(xpath(“/order/product=‘widget’”)).to(“amqp:queue:widget”)
.otherwise().to(“amqp:queue:gadget”);
}}
Component - technology or transport, 300+ existing components!
Endpoint - particular “instance” of Component with concrete configuration/params
Predicate - supports also JSONPath, OGNL and others
Route - DSL (chained methods) defining the message flow
Content Based Router - the Camel way
Component
Predicate Endpoint
Route

34. Camel - other concepts
● Integration with Spring
● Expression Languages
● Support for Spring Transactions (JDBC, JMS, 2PC)
● Data formats (XML, JSON, EDI, ...)
● Error handling / retry strategies
● Throttling
● Bean integration
● Graceful Shutdowns
● Excellent support for unit tests

35. Camel - deployment options
● Standalone Java JAR (camel-core is 4.5M)
● Embedded in Tomcat, Karaf (OSGi)
● As part of JBoss Fuse
● Spring-boot - my favorite!
● Basically just put it on classpath and use it!

36. Resources
● EIP Book: on Amazon
● https://www.enterpriseintegrationpatterns.com
● http://camel.apache.org/
● https://github.com/apache/camel/tree/master/examples
● Existing stencils for many modelling tools!

38. Thanks!
Any Questions?
I am a proud Camel Rider™ - feel
free to get in touch later or via DM!
See you later!
Later Gator!