moving from plexus to guice

Download Moving From Plexus To Guice

Post on 05-Jul-2015

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  • 1. Moving from to

2. Why move? Plexus is not widely used outside of Maven Lack of documentation, not always up-to-date Extra steps needed to generate Plexus XML Not type-safe, lacks support for generics 3. Single plexus.xml META-INF/plexus/components.xml (Class-Path) 4. Has annotations, but still need to generate XML 5. Why ? Standard: reference implementation for JSR 330 Flexible: can map all sorts of metadata to bindings Type-safe: detailed messages when things go wrong Modular:multiple extensions available, OSGi-ready 6. JSR 330 New standard for Java dependency injection // Constructor injection// Field injection// Setter injection 7. Fluent Java binding API Records generic information lost during erasure Can be driven by Java / annotations / XML / ...etc... 8. Migration Path Preserve investment in legacy Plexus components Allow gradual migration to JSR 330 annotations Must support mixture of Plexus and JSR 330 9. Customizing Guice provides an SPI to hook into injections TypeListeners called for matching bound types Register MembersListeners for custom injection Register InjectionListeners for custom lifecycles SPI supports binding introspection / rewriting 10. Injection Listeners 11. -y Beans Writing all those listener classes can get tedious guice-bean library cuts out most of the work You provide a BeanBinder implementation that can provide PropertyBinders for each type which can supply PropertyBindings for each property Bean conventions select field / setter properties 12. Compatibility Shim 13. Metadata Canonical form of Plexus bindings Captures @Component implementations Maps @Component bean properties to @Requirement settings @Configuration settings Interns Plexus hint strings to save space 14. Scanning for Metadata ClassSpace abstraction supplies classes / resources Can be backed by Plexus Classworlds or OSGi Plexus XML mapped into Plexus annotations Plexus annotations are interpolated and stored 15. ConvertingConfiguration Builds on top of standard Guice TypeConverters Supports properties, nested collections, and beans Guice SPI lets you add your own TypeConverters 16. Locating Components Guice bindings map Keys to Providers Each Key has a type and optional annotation Plexus components have roles and hints Key == Class + @Named(hint) Uses Guice SPI to find component bindings 17. BindingComponents Opposite of locating components @Component roles and hints turned into Keys Keys used to bind component implementations Singleton default, unless strategy is "per-lookup" 18. Injecting Requirements @Requirement locate Plexus components Handles Maps, Lists, instances, and Wildcards Loggers automatically configured and injected @Configurationconvert constant using type 19. ManagingLifecycles Uses an InjectionListener to listen for bean instances Plexus lifecycle "personality" applied after injection Reverse lifecycle applied when container disposed Need to manage extra metadata (like descriptions) 20. Time for a Demonstration! 21. Classworlds Plexus Container API still depends on Classworlds But dependency is much less in guice-plexus-shim Just need to write classworlds-shim around OSGi ... to get Plexus apps running on OSGi containers 22. Extending JSR 330 JSR 330 tells us how to mark dependencies and qualify them (just like with Plexus hints) But it does not say how to mark components 23. Identifying JSR 330 components Wrap the Class-Path up as a ClassSpace and scan it Look for classes with qualifiers such as @Named Empty @Named means "use class name" instead Binding type found by analysing class hierarchy 24. Next Steps We can now run Plexus apps on top of Guice ... and start separating apps into OSGi bundles OSGi lets us dynamically add / remove bundles ... but Guice bindings are static 25. Next Steps How can we resolve this mismatch? Find out in "Dynamic Guice Applications" ... 26. Links JSR 330http://code.google.com/p/atinject/ Guicehttp://code.google.com/p/google-guice/ Spice-Inject http://svn.sonatype.org/spice/trunk/spice-inject OSGi http://www.osgi.org/About/HowOSGi Blog Updates http://www.sonatype.com/people/author/mcculls/ 27. Questions? 28. Transfo rm ing th e w ay so ftw are is m ad e .