Introduction to ESBs:Mule

UC San DiegoCSE 294

November 14, 2008Barry Demchak

Agenda

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

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]

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

Definition(s)

Gartner Group

Giant exercise in Separation of Concerns

[Ric]

Definitions (more)

www.datapower.com

[Ric]

ESB Features

Routing Message Transformation Message Enhancement Protocol Transformation Service Mapping

Message Processing Process Choreography Service Orchestration Transaction Management Security

[Ric]

An ESB Blueprint

General case

Client calls Choreographer Client calls Mediator

vs

[Ric]

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]

JBI Example

XSLT – message transformation PXE – choreography Groovy – scripting

[Ric]

JBI Case Study: Service Mix

Service Mix

Binding Components

Service Engines

[Ric]

Mule Architecture

[Mule]

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]

Mule Connector View

http://myapp.com pop3://user@userland.comhttp→xml xml→pop3

myUMO (xml→xml)

[Mule]

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

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]

Mule Programming Model

Application logic

Application glue

Mule glue

[Mule]

Mule Routers

[Mule]

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>

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>

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>

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}

ESB Features

Routing Message Transformation Message Enhancement Protocol Transformation Service Mapping

Message Processing Process Choreography Service Orchestration Transaction Management Security

XX

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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