Whoops! Where did my architecture go?

Whoops! Where did my architecture go?Approaches to architecture management for Java and Spring applications Oliver Gierke

Oliver GierkeSpringSource EngineerSpring Dataogierke@vmware.comolivergierkewww.olivergierke.de

Background 5 years of consulting Lots of code reviewsEoin Woods‘ talk on InfoQ

Roadmap Architecture 101A plain Java based approach Hera

The 3 C ofArchitecture Constraints Complexity Change © Uwe Friedrichsen

The 2 Cs ofArchitecture Complexity Change

Architecture 101

Know yourdependencies

Granularity Modules Layers Vertical slices Subsystems

Granularity Java ARchive Package Class

Of layersand slices…

Slice A Slice B Slice CLayer 1Layer 2Layer 3

Layers Well understood Known to developersLess important to business

SlicesHardly understoodNew to developersKey for business req

" How to implement an architecture inside a codebase?

Architecture VS. Codebase

" How to implement an architecture inside a codebase?

" How to enforce an architecture inside a codebase?

Code analysis JDepend Sonar

SonargraphFormerly known as SonarJ

A plain Javabased approach

" How far can we get with plain Java means only?

Packages

….${layer}.${slice} VS.….${slice}.${layer}

…domain.core …service.core…repository.core

…core.domain …core.service…core.repository

Layers ﬁrst Leaks slice internalsLower layers visible to everyone

" Start with less packages and the least visibility possible…

Slices ﬁrst Start with package per sliceExpose interfaces and domain types Keep implementations private

Slices ﬁrstEncapsulates business moduleInternals understood anyway

Subsystems

Background Risk mgmt. at German public bankQuite a few other SpringSource clients

Systemsgrow big!

Rememberthe 2 Cs?

Complexity & Change

" How to localize change?

" Separate frequent from infrequent change!

Granularity Class Package Java ARchive

HostSPI SPI SPI Plugin Plugin

Context No OSGi Spring based Build-time compositionDon‘t touch the host system

AppPlugin Plugin Host

" How to make the host aware of the plugins?

" How to dynamically collect Spring beans of a given type?

classpath*:META-INF/spring/plugin-context.xml

HostSPI SPI SPI Plugin Plugin

classpath*:META-INF/ spring/plugin-context.xmlSPI SPI SPI META-INF/ META-INF/spring/plugin- spring/plugin- context.xml context.xml

@Componentpublic class MyComponentImpl implements TransferService { private List<MyPlugin> plugins; @Autowired public MyComponentImpl(List<MyPlugin> plugins) { this.plugins = plugins; } …}public interface MyPlugin { void doSomething();}

XML?Back in the days

(XML?) Back in the daysProbably not a big deal anymore

Easy access?

@Componentpublic class MyComponentImpl implements TransferService { private List<MyPlugin> plugins; @Autowired public MyComponentImpl(List<MyPlugin> plugins) { this.plugins = plugins; } …}public interface MyPlugin { void doSomething();}

@Componentpublic class MyComponentImpl implements TransferService { // Constructor omitted public Result myMethod(SomeParameter parameter) { // Select the ﬁrst one to match to invoke? // Select multiple ones to invoke? // Select and fallback to one if none found? // Select and throw an exception if none found? }}

" The smallest plugin system ever!

Plugins Selection criterion Callback methodLet the implementation decide

Registry Equipped with pluginsCommon access patterns

public interface Plugin<T> { public boolean supports(T delimiter );}public interface PluginRegistry<S extends Plugin<T>, T> { T getPluginFor(S delimiter); T getPluginFor(S delimiter, T default); <E extends Exception> T getPluginFor(S del, E e) throws E; List<T> getPluginsFor(S delimiter); …}

@Componentpublic class MyComponentImpl implements TransferService { private PluginRegistry<MyPlugin, String> plugins; @Autowired public MyComponentImpl( PluginRegistry<MyPlugin, String> plugins) { this.plugins = plugins; }}public interface MyPlugin extends Plugin<String> { void doSomething();}

@Componentpublic class MyComponentImpl implements TransferService { private ﬁnal MyPlugin defaultPlugin = new MyDefaultPlugin(); public Result myMethod(String parameter) { // Select the ﬁrst one to match to invoke? … = plugins.getPluginFor(parameter); // Select multiple ones to invoke? … = plugins.getPluginsFor(parameter); // Select and fallback to one if none found? … = plugins.getPluginFor(parameter, defaultPlugin); // Select and throw an exception if none found? … = plugins.getPluginsFor(parameter, new RuntimeException()); }}

OrderAwarePluginRegistryRespects @Order/Ordered OAPR.reverse()

Bells‘n‘whistles FactoryBean Spring namespace Lazy-eval

Herahttp://hera.synyx.org Apache 2.0Soon to be on GitHub

Spring Integration2

Take-aways Know your dependencies On every granularity Start as strict as possibleGet lenient where necessary

Thanks & credits Eoin Woods - Talk @ InfoQUwe Friedrichsen - Slides @ Slideshare

ResourcesSpring Data JPA @ GitHub Sonargraph Hera

http://www.martinahrer.at	269
http://coridio.blogspot.com.es	204
http://coridio.blogspot.com	197
http://www.jmiguel.eu	129
http://coridio.blogspot.mx	17
http://7750988227162852637_918681e8b4e5d809479869c975077ff9f98da2f9.blogspot.com	9
http://feeds.feedburner.com	7
http://coridio.blogspot.com.ar	6
https://twitter.com	5
http://coridio.blogspot.com.br	3
http://coridio.blogspot.de	1
http://coridio.blogspot.ch	1
http://www.coridio.blogspot.com.ar	1
http://translate.googleusercontent.com	1
http://a0.twimg.com	1
http://coridio.blogspot.fr	1
http://blog.eisele.net	1
http://www.directrss.co.il	1

Whoops! Where did my architecture go?

by Oliver Gierke

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