Whoops! Where did my architecture go?

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

Oliver Gierke


Oliver Gierke

Spring DataCore/JPA/MongoDB

[email protected]

mailto:[email protected]

mailto:[email protected]

http://www.olivergierke.de

http://www.olivergierke.de


BackgroundFew years of consulting

Lots of code reviewsEoin Woods‘ talk on InfoQ


RoadmapArchitecture 101

A Java packages modelHera


Architecture 101


Know your dependencies


GranularityModulesLayers

Vertical slicesSubsystems


GranularityJava ARchive

PackageClass


Of layersand slices…


Layer 1

Layer 2

Layer 3

Slice A Slice B Slice C


LayersWell understood

Known to developersLess important to business


SlicesHardly understoodNew to developers

Key for business req


Layer 1

Layer 2

Layer 3



"How to implement an architectureinside a codebase?


ArchitectureVS.

Codebase


"How to implement an architectureinside a codebase?


"How to enforcean architectureinside a codebase?


Code analysisJDepend

Sonar


Demo


SonargraphFormerly known as SonarJ


Demo


A plain Javabased approach


Layer 1

Layer 2

Layer 3



….${layer}.${slice}VS.

….${slice}.${layer}


Layers firstLeaks slice internals

Lower layers visible to everyone


"Start with less packages and the least visibility possible…


Layer 1

Layer 2

Layer 3



Layer 1

Layer 2

Layer 3



Slices firstStart with package per slice

Expose interfaces and domain typesKeep implementations private


Slices firstEncapsulates business moduleInternals understood anyway


Subsystems


BackgroundRisk mgmt. at German public bank

Quite a few other SpringSource clients


"The smallest plugin systemever!


Host

SPI SPI SPI

Plugin Plugin


ContextNo OSGi

Spring basedBuild-time composition

Don‘t touch the host system


Host

Plugin Plugin

App


"How to make the host aware of the plugins?


"How to dynami-cally collect Spring beans of a given type?


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


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

SPI SPI SPI

META-INF/spring/plugin-context.xml

META-INF/spring/plugin-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();

}


Demo


XML?Back in the days


(XML?)Back in the days

Probably not a big deal anymore


Easy access?



private List<MyPlugin> plugins;

@Autowired public MyComponentImpl(List<MyPlugin> plugins) { this.plugins = plugins; } …}

public interface MyPlugin {void doSomething();

}



// 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?

}}


PluginsSelection criterionCallback method

Let the implementation decide


RegistryEquipped with plugins

Common 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 exception) throws E;

List<T> getPluginsFor(S delimiter);…

}



private PluginRegistry<MyPlugin, String> plugins;

@Autowired public MyComponentImpl(PluginRegistry<MyPlugin, String> plugins) { this.plugins = plugins; } …}

public interface MyPlugin extends Plugin<String> {void doSomething();

}



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‘whistlesFactoryBean

Spring namespaceLazy-eval


Hera


Herahttp://hera.synyx.org

Apache 2.0Soon to be on GitHub


Spring Integration2


<bean class="….FirstSamplePlugin" /><bean class="….SecondSamplePlugin" />

<int:channel id="input" /><int:channel id="output" />

<int-hera:dynamic-service-activatorinput-channel="input" outputChannel="output" plugin-type= "….MyPlugin" method= "myBusinessMethod"delimiter="payload" invocation-arguments= "payload" />


Demo


Take-awaysKnow your dependencies

On every granularityStart as strict as possible

Get lenient where necessary


Thanks & creditsEoin Woods - Talk @ InfoQ

http://www.infoq.com/presentations/Where-Did-My-Architecture-Go

http://www.infoq.com/presentations/Where-Did-My-Architecture-Go


ResourcesSourcecode @ GitHub

Sonargraph

https://github.com/olivergierke/whoops-architecture

https://github.com/olivergierke/whoops-architecture

http://www.hello2morrow.com/products/sonargraph

http://www.hello2morrow.com/products/sonargraph

Technology

Whoops! Where did my architecture go?