Mule is an open source enterprise service bus (ESB) that addresses integration problems by enabling the refactoring of existing systems in real-time as requirements change. It provides routing, transformation, and management of messages between disparate systems. Mule uses connectors to integrate applications together through its flow-based visual programming model and supports many transports and protocols.

1. Introduction to ESBs:
Mule
Khan

2. Agenda
 What is an ESB?
 Java Business Integration (JBI)
 Mule Architecture
 Mule in the Real World

3. Source Material
 [Ric] Mark Richards, “The Role of the
Enterprise Service Bus”, NFJS, Oct 23,
2006. http://www.infoq.com/presentations/Enterprise-Service-Bus
 [Mul] Mule Architecture Guide.
http://mule.mulesource.org/display/MULE/Architecture+Guide
 September [mule-user archive]

4. Problems Addressed by ESBs
 Integration of existing systems
 Refactorable in real time
 Flexibility to change as requirements change
 Decentralized (service-location transparency)
 Scalable (point solutions to full enterprise)
 Sharing of services across enterprise
 Ability to separate Business Services from
Service Implementations
 Leverages standards

5. Definition(s)
Gartner Group
Giant exercise in Separation of Concerns
[Ric]

6. Definitions (more)
www.datapower.com
[Ric]

7. ESB Features
 Routing
 Message Transformation
 Message Enhancement
 Protocol Transformation
 Service Mapping
 Message Processing
 Process Choreography
 Service Orchestration
 Transaction Management
 Security
[Ric]

8. An ESB Blueprint
General case
Client calls Choreographer Client calls Mediator
vs
[Ric]

9. Java Business Integration (JBI)
 JSR-208 Standard
 Defines service engines (SE – choreographers,
transformers, security, etc) and binding components
(BC – xml, http, etc)
 Concerned with how internal customers (not external
services) interact with service providers
COTS
[Ric]

10. JBI Example
 XSLT – message transformation
 PXE – choreography
 Groovy – scripting
[Ric]

11. JBI Case Study: Service Mix
Service Mix
Binding Components
Service Engines
[Ric]

12. Mule Architecture
[Mule]

13. Mule Flow View
 Channel – a method of connecting between two points (not part
of Mule)
 Connector – a transport provider (e.g., http, jms, soap, smtp,
etc) implementing message receive and message dispatch
 Transformer – converts message structure/format (e.g., http to
xml)
 Router – moves messages amongst UMOs and connectors
[Mule]

14. Mule Connector View
http://myapp.com pop3://user@userland.comhttp→xml xml→pop3
myUMO (xml→xml)
[Mule]

15. Mule Transports
 AS400 DQ
 EJB
 E-mail
 File
 FTP
 HTTP
 IMAP
 JDBC
 JMS
 Multicast
 POP3
 Quartz
RMI
 Servlet
 SMTP
 SOAP
 SSL
 Stream
 TCP
 UDP
 VFS
 VM
 WSDL
 XMPP

16. UMO Execution
 Requires a component resolver (e.g., Spring
or Pico) for
 Instantiation of UMOs
 Configuration of UMOs
 Event processing
 Asynchronous
 Synchronous
 Request-Response
[Mule]

17. Mule Programming Model
Application logic
Application glue
Mule glue
[Mule]

18. Mule Routers
[Mule]

19. Selective Consumer (inbound)
 Applies one or more filters to incoming payload, then
branch based on filter
<inbound-router>
<catch-all-strategy
className="org.mule.routing.ForwardingCatchAllStrategy">
<endpoint address="jms://topic:error.topic"/>
</catch-all-strategy>
<router
className="org.mule.routing.inbound.SelectiveConsumer">
<filter expression="msg/header/resultcode = 'success'"
className="org.mule.routing.filters.xml.JXPathFilter"/>
</router>
</inbound-router>

20. Filtering Outbound (outbound)
<outbound-router>
<catch-all-strategy
className="org.mule.routing.ForwardingCatchAllStrategy">
<endpoint="jms://error.queue"/>
</catch-all-strategy>
<router className="org.mule.routing.outbound.FilteringOutboundRouter">
<endpoint address="smtp://ross@muleumo.org"/>
<filter expectedType="java.lang.Exception"
className="org.mule.routing.filters.PayloadTypeFilter"/>
</router>
<router className="org.mule.routing.outbound.FilteringOutboundRouter">
<endpoint address="jms://string.queue"/>
<filter className="org.mule.routing.filters.logic.AndFilter">
<left-filter expectedType="java.lang.String"
className="org.mule.routing.filters.PayloadTypeFilter"/>
<right-filter pattern="the quick brown (.*)"
className="org.mule.routing.filters.RegExFilter"/>
</filter>
</router>
</outbound-router>

21. Nested Router
 Allows synchronous callouts that can be intercepted and routed
<mule-descriptor name="InvokerComponent"
implementation="org.mule.foo.Invoker">
<inbound-router>
<endpoint address="jms://Invoker.in"/>
</inbound-router>
<nested-router>
<binding interface="org.mule.foo.HelloInterface">
<endpoint
address="axis:http://192.168.2.14:81/services/HelloWebComponent?
method=helloMethod" remoteSync="true"/>
</binding>
</nested-router>
<outbound-router>
<router
className="org.mule.routing.outbound.OutboundPassThroughRouter">
<endpoint address="jms://Invoker.out"/>
</router>
</outbound-router>
</mule-descriptor>

22. Dog Days with Mule
 September [mule-user archive]
 How to get a hold of Endpoint object from the
component? {mule}
 Failed to throw UserDefined Exception {jaxws}
 Failed to invoke lifecycle “start” using CXF in
JBOSS {cxf}
 Problem in loading xsd files {mule}
 Problems with RemoteDispatcher {mule}
 Inject MuleClient Singleton with Spring {mule}
 Mule transaction support {mule}

23. ESB Features
 Routing
 Message Transformation
 Message Enhancement
 Protocol Transformation
 Service Mapping
 Message Processing
 Process Choreography
 Service Orchestration
 Transaction Management
 Security
X
X
√
√
√
√
√

24. Take Away Messages
 Mule’s generality results in great flexibility, but at the
cost of great complexity for users
 Mule is the focal point of ambiguity and difficulties
with many standards-based packages
 Mule delivers (to a degree) on:
 Integration, flexibility, decentralized operation,
scalability
 Mule doesn’t deliver (so much) on:
 Runtime refactoring, conceptualization