Monoliths are so 2001 – What you need is Modularity

© 2015 IBM Corporation
Monoliths are so 2001 –
What you need is
Modularity
Graham Charters, STSM, WebSphere Liberty
Repository & OSGi Applications Architect
Ian Robinson, Distinguished Engineer,
WebSphere Foundation Chief Architect

Agenda
• Monoliths & Modularity
• Modularity and Java
• Introduction to OSGi
• Dismantling the Monolith
• A Case Study – Acme Air
• What’s new in OSGi Applications
• Summary
1

Why Monoliths
• No project sets out to create a
monolith
• Projects evolve
• Teams evolve
• Architecture knowledge is lost
leading to sub-optimal decisions

How do we preserve knowledge?
• Design documentation?
• Wiki?
• Email?
• Work items?
• IRC?
• Brain?
• Developers make the decisions, and where do they hang out?
4
We need to capture and enforce the architectural knowledge in the code

Modularity
• Concept of Modularity in Software dates back to the 1960
• For a module systems to preserve architectural knowledge it needs the follow
qualities
• Reflect the right level(s) of architectural granularity
• Support the Reuse/Release Equivalence Principle
• Capture modularity information in the code
• Enforce modularity
5
None of your
business
What I can
provide to you
What I will need
from you

7
Base Java modularity is inadequate
• Classes too fine-grained
• Jars are packaging with no explicit
requirements/capabilities
• Linear classpath
Java EE modularity is inadequate
• Across apps - each archive typically contains
all required libraries
• Common libraries/frameworks get
installed with each application
• Multiple copies of libraries in memory
• Within apps - 3rd party libraries
consume other 3rd party libraries
leading to conflicting versions on
the application classpath.
webB.war
WEB-INF/classes/servletB.class
WEB-INF/lib/json4j.jar
WEB-INF/lib/commons-logging.jar
WEB-INF/lib/junit.jar…
webC.war
WEB-INF/classes/servletC.class
WEB-INF/lib/json4j.jar
WEB-INF/lib/commons-logging.jar
WEB-INF/lib/junit.jar…
plankton.v1
plankton.v2
Modularity Issues in Java EE

9
Bundle
Manifest-Version: 1.0
Bundle-ManifestVersion: 2
Bundle-ManifestVersion: 2
Bundle-Name: My Example Bundle
Bundle-SymbolicName: com.my.bundle
Bundle-Version: 1.0.0
Export-Package: com.something.i.provide;version="1.0.0"
Import-Package: com.something.i.need;version="[1.1,2.0)"
Bundle
Bundle
Bundle
Manifest-Version : 1.0
Bundle-ManifestVersi
OSGi Modules (aka Bundles)
• A Jar plus OSGi Manifest, includes:
• Bundle Identity
• Exported Packages
• Imported Packages
• Dependency resolution
“wires” bundles into
a dependency graph
• Each gets its own
class loader
• Classloading
delegates via graph
Classloader
Classloader
Classloader
Classloader

10
Dynamic Bundle Lifecycle
• Bundles have a dynamic
lifecycle
• Can come and go
independently
• APIs enable graceful
reaction to changes
Bundle
INSTALLED
RESOLVED
UNINSTALLED
STARTING
ACTIVE
STOPPING
install
update
refresh
uninstall
update
refresh
stop
policy
resolve
uninstall

11
Local Services
• Publish/find/bind service model
• Fully dynamic
• Local
• Non-durable
• Primary mechanism for bundle collaboration
• POJO advertized with properties and/or interface and/or
class
service
Provider
Bundle
Consumer
Bundle
registerget
listen

Background
• First surfaced to applications in a WAS v7 Feature Pack
• http://www-01.ibm.com/software/webservers/appserv/was/featurepacks/
• Modular development, deployment and management
• Blueprint (Standardized Spring Component Model)
• Web applications (Java EE 5)
• Remote Services and Heterogeneous Assembly (SCA)
• Included in the WAS Base in v8 and continually extended:
• Java EE 6 Web technologies
• Post-deployment configuration
• Performance metrics
• In-place Update
• Application Extension
• Modular EJB
• Blueprint Role-based Security
• OSGi Applications Web Console
• Liberty Profile support
13

Component Models
Category Full Profile Liberty Profile
Presentation Servlet, JSP, JSF Servlet, JSP, JSF
Business Blueprint*, EJB Blueprint*
Persistence JPA, JDBC JPA, JDBC
Integration JAX-RS, JMS, SCA JAX-RS, JAX-WS, JMS
14
Component models for enterprise Web applications
Re-use rather than re-invent
• Java EE, Spring
*some differences in supported namespaces

Web Application Bundle
• Web Application Bundle (WAB) = WAR + OSGi metadata
• Web-ContextPath: header used to specify default context root
• OSGi Manages
• Module Lifecycle
• Classloading (opportunity to split out WEB-INF/lib)
• Service Integration
• Web Container Manages
• Web component life-cycle, serving, etc...
webC.war
logging f/w
persistence f/w
MVC f/w
webB.war
logging f/w
persistence f/w
MVC f/w
webA.war
logging f/w
persistence f/w
...
WEB-INF/classes/servletA.class
WEB-INF/web.xml
WEB-INF/lib/…
webA.jar
WEB-INF/web.xml
META-INF/MANIFEST.MF
webA.jar
WEB-INF/web.xml
webA.jar
WEB-INF/web.xml
logging f/w
persistence f/w
...
These can
become shared
bundles

Bundle
Blueprint Components and Service
• Dependency Injection container
• Standardizing established Spring conventions
• Configuration and dependencies declared in Blueprint XML
• Standardization of Spring “application context” XML
• Extended for OSGi: publish/consume components as OSGi services
• Simplifies unit test outside either Java EE or OSGi r/t
• Integrated into server runtime to simplify deployment & support
16
dependencies injected
publishes
service
consumes
service
Blueprint container scoped by
a bundle (one per bundle).
Multiple <blueprints /> per
container.
A static assembly and
configuration of beans
(POJOs)
Blueprint managed bundle

Brightness
Blueprint Extensions
• Namespaces extend core component model
• Transactions
• Resource References (Full Profile)
• JPA integration
• Security (Full Profile)
• Third-party (Liberty 8.5.5.3)
<blueprint xmlns="http://www.osgi.org/xmlns/blueprint/v1.0.0"
xmlns:sec="http://www.ibm.com/appserver/schemas/8.0/blueprint/security"
xmlns:tx="http://aries.apache.org/xmlns/transactions/v1.0.0">
<service id="adjustmentService" ref="BrightnessDeltaBean"
interface="colors.adjustment.api.BrightnessService">
</service>
<bean id="BrightnessDeltaBean"
class="colors.brightness.BrightnessDelta">
<sec:access-constraint method="setBrightnessDelta" role="adjuster" />
<tx:transaction method="*" value="Required" />
<jpa:context property="em" unitname="brightnessUnit"/>
<property name="delta" value="100"/>
</bean>
</blueprint>

EJB Bundle
• EJB Bundle = EJB Jar + OSGi Metadata
• Export-EJB: Opt-in header for EJB Bundles
– Existence: process bundle for EJBs
– Absence: do not process bundle for EJBs, even if it contains them
• Header value governs registration of EJBs as OSGi Services
– Excludes Message-Driven and Stateful beans
– Best practice: only export EJBs to be shared outside bundle
• EJBs run in the same WAS EJB Container
• Uses OSGi for Classloading and Life-cycle
18
Example Meaning
Export-EJB: Process all EJBs and register them as OSGi services
Export-EJB: BlogBiz,
BlogPersistence
Process all EJBs, register BlogBiz and BlogPersistence as
services if they exist
Export-EJB: NONE Process all EJBs but don’t register them as OSGi services

Persistence Bundle
• Persistence Bundle = Persistence Archive + OSGi Metadata
• Meta-Persistence: opt-in header
• Identifies the location of the persistence xml file
• Defaults to META-INF/persistence.xml
• Datasource lookup mechanisms:
<jta-data-source>

blueprint:comp/blueprint_component_name
</jta-data-source>
<jta-data-source>
osgi:service/javax.sql.DataSource/(osgi.jndi.serviceName=
jndi_name_of_the_data_source)
</jta-data-source>
<jta-data-source>
jndi_name_of_the_data_source
</jta-data-source>

.eba
OSGi Application
• Isolated, cohesive collection
of bundles
• Defined by application
manifest
• Configuration by
exception
• Deployed as .eba archive (zip
file)
• Provisioning resolves
application against archive
contents and configured
bundle repositories
APPLICATION.MF
Application-Name: Color Blender Application
Application-SymbolicName: colors.blender.simple.app
Application-ManifestVersion: 1.0
Application-Version: 1.0.1
Application-Content:
colors.blender;version="[1.0.0,2.0.0)",
colors.provider.green;version="[1.0.0,2.0.0)",
colors.provider.red;version="[1.0.0,2.0.0)",
colors.web;version="[1.0.0,2.0.0)",
colors.provider.ejb.blue;version="[1.0.0,2.0.0)"
Application-ImportService:
colors.adjustment.api.BrightnessService
Application-Name: Color Blender Application
Application-SymbolicName:
colors.blender.simple.app
Application-ManifestVersion: 1.0
Application-Version: 1.0.1
colors.blender;version="[1.0.0,2.0.0)",
colors.provider.green;version="[1.0.0,2.0.0)",
colors.provider.red;version="[1.0.0,2.0.0)",
colors.web;version="[1.0.0,2.0.0)",
colors.provider.ejb.blue;version="[1.0.0,2.0.0)"
Application-ImportService:
colors.adjustment.api.BrightnessService
colors.web
colors.blender

OSGi Application Provisioning
• Application manifest allows
version ranges for contents
• Deployment Manifest
(optional) locks down exact
versions
• Provisioning resolves
application against archive
contents and configured
bundle repositories
• Non-content bundles satisfy
unresolved application
package and service
dependencies
• shared between
applications on same
server
.eba
APPLICATION.MF
DEPLOYMENT.MF
colors.api
colors.
web
colors.
blendercolors.
provider.
blue
Shared Bundles
colors.
blender
OSGi Application
colors.
provider.
blue
colors.api
colors.
web

Adoption Strategies
• Favoured Java EE Approach:
1. Replicate existing classloading in OSGi using bundle fragments
2. Incrementally separate out individual bundles
3. Adopt OSGi best practices
• Considers Java EE classloading and component models
• Surfaces OSGi early, and incrementally - a staged approach
23
beans
core
ejb3
entities
json-proxy
soap
wsappclient
streamer
web
app-host
logcoreejb3
wab
web
app-host
logcoreejb3
wab
web
log
http://www.slideshare.net/GrahamCharters/modularizing-existingenterpriseapplicationsos-gicommunityevent2012v01

Stage 1: Understanding the starting point
• Java EE prescribes a hierarchical
classloading model
• Assuming “parent first” and “multiple”:
• Each Application has own
classloader
• Each WAR has own class loader
• WAR has visibility to Application
classes
• WAR prefers Application classs,
Application prefers System classes,
etc...
• OSGi modularity enforced through class
visibility using classloaders
• Migration strategies need to consider the
impact of this change
• e.g. replicate visibility relationships
of existing application in OSGi
24
Bootstrap
Extensions
System
Application Application
WAR WAR WAR

Stage 1: Replicating Java EE classloading
• Preserve Application and WAR roles
• Application -> Application Host
Bundle
• Add application modules to
fragments of host bundle
• Web App Archive -> Web Application
Bundle
• Add WEB-INF/classes to
Bundle-Classpath
• Extract WEB-INF/lib jars and
add as fragments of Web
Application Bundle
• We now have two classloaders just as
we did in Java EE 
• We also have full visibility of the
modules
25
System
Application
WAR
app-host
logcoreejb3
wab
web

Stage 2: Factoring out Bundles
• Now the application’s running in OSGi we can start to split out the
fragments as independent, re-usable bundles
• Strategy:
• Do one fragment at a time
• Start with the leaf dependencies
– Wab bundle contents first, then the app bundle
– Project build dependencies help with identification
– Third-party libraries
– “shared libraries” (if runtime supports this concept)
• Detach from host and calculate the package imports & exports
26
wab
web
wab
web
Fragment-Host: wab Export-Package: daytrader.web
Import-Package: daytrader.web

Stage 3: Incrementally Adopt Best Practices
• Stage 2 documents the ‘as-is’ architecture, warts-‘n’-all
• OSGi Best Practices show how to make the most of OSGi
http://www.ibm.com/developerworks/websphere/techjournal/1007_charters/1007_charters.html
• Adopting best practices leads to:
• High cohesion - bundles with clear and distinct roles in the
architecture
• Loose coupling - flexible, but necessary, dependencies
• ...which all leads to greater agility, flexibility and re-use
• Development teams can understand and explain the architecture
and are no longer afraid to change the code
• Applications can evolve and new application can be created at a
pace that enables, rather than inhibits, the business
27

Acme Air
• A Sample Java EE Web Application
• Key Technologies
• Web content - html, JavaScript
• REST APIs - JAX-RS
• Persistence – JPA
• Spring
• Built using Maven
• Deployed as a WAR with all the
dependencies inside (WEB-INF/lib)
acmeair-webapp.war
acmeair-common.jar
acmeair-service.jar
springxxx.jar
WEB-INF/classes/xxx.class
WEB-INF/web.xml
WEB-INF/lib/…
...
29

Stage 1 - 1 = 0: Single Bundle
• Single monolithic bundle
• Build a WAB not a WAR
• Web–ContextRoot
• Bundle-Classpath
• Package imports
• Uses JPA so also make it a Persistence
Bundle
• Change use java:comp/env to
osgi:service
• Address classpath issues (e.g. Spring
@ComponentScan, file loading)
31
acmeair-webapp.war
acmeair-common.jar
acmeair-service.jar
springxxx.jar
WEB-INF/web.xml
WEB-INF/lib/…
acmeair-webapp-bundle.jar
WEB-INF/web.xml
...
<plugin>
<groupId>org.apache.felix</groupId>
<artifactId>maven-bundle-plugin</artifactId>
<version>2.5.3</version>
<extensions>true</extensions>
<configuration>
<instructions>
<Web-ContextPath>/acme.air.osgi</Web-ContextPath>
<Embed-Dependency>*;scope=compile</Embed-Dependency>
<Bundle-Classpath>WEB-INF/classes</Bundle-Classpath>
<Embed-Transitive>true</Embed-Transitive>
<Meta-Persistence>
WEB-INF/classes/META-INF/persistence.xml
</Meta-Persistence>
<Import-Package>
!javax.resource,
!javax.resource.cci,
!javax.resource.spi,
...
javax.*,
org.xml.sax,
org.w3c.dom
</Import-Package>
<_wab>src/main/webapp</_wab>
</instructions>
</configuration>
</plugin>
acmeair-common.jar
acmeair-service.jar
springxxx.jar
...

Stage 1: OSGi Application
• Build an OSGi Application
(EBA) to deploy the WAB
• Eba-maven-plugin generates
application manifest based on
pom configuration
32
acmeair.eba
META-INF/APPLICATION.MF
<plugin>
<groupId>org.apache.aries</groupId>
<artifactId>eba-maven-plugin</artifactId>
<configuration>
<generateManifest>true</generateManifest>
<instructions>
<Application-SymbolicName>
${project.artifactId}
</Application-SymbolicName>
</instructions>
</configuration>
</plugin>
Application-ManifestVersion: 1
Application-SymbolicName: acmeair-eba
Application-Version: 1.0.0.SNAPSHOT
Application-Name: acmeair osgi application
Application-Description: AcmeAir Application
net.wasdev.wlp.sample.acmeair-webapp-bundle;version="1.0.0.SNAPSHOT"

Stage 1: Fragments
• Fragments used to separate out “modules”
from WAB without affecting classloading
• Update EBA to include Fragments
• First opportunity to see the true package
dependencies
• Opportunity for small refactoring (e.g.
persistence.xml from WAB to persistence
fragment)
33
WEB-INF/web.xml
springxxx.jar
acmeair-common-bundle.jar
acmeair-service-bundle.jar
acmeair-service-jpa-bundle.jar
<plugin>
<configuration>
<instructions>
<Fragment-Host>
net.wasdev.wlp.sample.acmeair-webapp-bundle
</Fragment-Host>
</instructions>
</configuration>
</plugin>
persistence.xml

Stage 2: Bundles
• Detach Fragments from Host
• Move opt-in headers from Host to new
bundles
• Export packages from Host, if
necessary (e.g. Spring)
• Separation Issue: webapp bootstraps
spring beans from service-jpa then
looks them up
34
WEB-INF/web.xml
springxxx.jar
acmeair-service-bundle.jar
persistence.xml
<plugin>
<configuration>
<instructions>
<Meta-Persistence>
META-INF/persistence.xml
</Meta-Persistence>
</instructions>
</configuration>
</plugin>

Stage 2: Bundles...not quite
• Webapp uses a singleton “ServiceLocator” to get the Spring beans
• Webapp ServiceLocator bootstraps the Spring application context
by trying to load config from the service-jpa bundle but can’t find it
• @ImportResource({"classpath:/spring-config.xml"})
• These modules are too tightly couple and so can’t function
independently.
35
WEB-INF/web.xml
springxxx.jar
@ImportResource({"classpath:/spring-config.xml"})
spring-config.xml

Stage 2 & 3: Bundles...almost
• ServiceLocator is acting as a Service Registry. OSGi has one of
those.
• Bundle Activator used to bootstrap Spring application context and
register bean services
• Also needed to register EntityManager service for Spring
• Webapp changed to load services from Service Registry
36
WEB-INF/web.xml
springxxx.jar
spring-config.xml
SpringActivator
@ImportResource({"classpath:/spring-config.xml"})
ic.lookup("osgi:service/acmeair.CustomerService")

Stage 2 & 3: Bundles
• But... there’s still a slight
issues... lifecycle
• Can’t bootstrap Spring if the
Persistence support is not ready
• Could “sleep”, but for how long?
• Solution: use a service lifecycle-
aware component model
(Blueprint)
37
spring-config.xml
EntityManagerFactory
<blueprint
xmlns="http://www.osgi.org/xmlns/blueprint/v1.0.0">
<bean id="SpringContextInitializerBean"
class="com.acmeair.jpa.service.config.SpringContextInitializer">
<property name="ctxt" ref="blueprintBundleContext" />
<property name="emf" ref="emf" />
</bean>
<reference id="emf"
interface="javax.persistence.EntityManagerFactory“ />
</blueprint>
blueprint.xml

Was it worth it?
• A set of modules re-usable at different levels
• Persistence
• Local Domain Services
• Remote REST Services
• Looser-coupling and higher cohesion
• No persistence content in the Web front-end
• Spring isolated to the module that uses it
• Flexible lifecycle
38
acmeair-webapp-bundle.jar acmeair-service-jpa-bundle.jar acmeair-common-bundle.jar

What’s new in WebSphere OSGi Applications
Liberty had addressed a number of top customer requirements through 2014
• Customer Blueprint Namespace Handlers
• Use cases: CXF, Camel, Config Adnim, etc…
• External Bundle Repositories
• Use cases: Rational Asset Manager, Nexus integration
• Local Application to application integration
• Use cases: Application interaction, ‘extension’
• JAX-RS & JAX-WS
• Use cases: Integration & Interop
• Subsystems (beta)
• Uses cases: extension and in-place update
• Be sure to raise RFE to help us prioritize your needs
• https://www.ibm.com/developerworks/rfe/

Summary
• Enforce right-scale modularity is key to preserving architectural
knowledge
• Even relatively simple applications can become entangled in the
absence of a good modularity
• A methodical approach to adopting OSGi can deliver results
early and dismantle the monolith
• WebSphere Application Server Liberty Profile is now an even
better platform for Enterprise OSGi

Notices and Disclaimers
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notice.
Performance data contained herein was generally obtained in a controlled, isolated environments. Customer examples are
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