Modularizing Your Grails Application with Private Plugins

SpringOne 2GX 2012
October 17, 2012

Transcript

1. Modularizing Your Grails Application with Private Plugins Ken Liu IEEE SpringOne 2GX 2012 17 Oct 2012 Wednesday, October 17, 12
2. About Me • Web development with Java since JDK 1.0.2 (applets, anyone?) • Groovy/Grails since 2009 • Lead developer for IEEE Spectrum • Always been a closet fan of dynamic languages (starting with Perl) Wednesday, October 17, 12
3. About IEEE • Institute of Electrical and Electronics Engineers • Widely known for standards - 802.11 • World’s largest technology professional association - 400,000 engineers in 160 countries • Publishes nearly a third of the world’s technical literature in EE/CS Wednesday, October 17, 12
4. About IEEE Spectrum • Flagship publication of IEEE • General interest technology magazine with focus on EE topics • 2012 National Magazine Award winner Wednesday, October 17, 12
5. IEEE Spectrum website • http://spectrum.ieee.org • ~1.5M PV/mo • Frequent referrals from HN, Reddit, /. • 100% Groovy/Grails since 2009 - both front-end and CMS • Akamai/Weblogic/Oracle stack • Award-winning coverage of ROBOTS! Wednesday, October 17, 12
6. Agenda • Grails plugins overview • Grails plugin development basics • Application architecture with private plugins • Lessons learned Wednesday, October 17, 12
7. To fork or not to fork? • “We need a new website...” • “You must use the standard corporate Enterprise CMS system.” • “Can’t you guys just make a copy of the existing code and tweak it?” • DANGER! Wednesday, October 17, 12
8. From “big ball of mud” to plugin architecture Front End Controllers/Views/ Services (e.g. article, blog pages) Domain classes (e.g Article, BlogPost) CMS Controllers/ Views/Services Quartz Jobs (e.g. sitemap generation) Spectrum Taglib Utility classes (src/**) UrlMappings Test classes Front End & CMS images, CSS, JS Where do we go from here? Wednesday, October 17, 12
9. • Grails plugins overview • Grails plugin development basics • Application architecture with private plugins • Lessons learned Agenda Wednesday, October 17, 12
10. Plugin systems and component models • Plugin systems are now commonplace • Firefox, Eclipse, Jenkins, JEdit • Package managers, OSGi, Ruby on Rails Engines • Component-oriented software? • Coarse-grained high-level reuse, separation of concerns Wednesday, October 17, 12
11. Grails plugins in a nutshell • Tightly integrated into Grails system • Can implement common functionality in plugins that is overridden by application • Can create new Artifact types • Interact with Spring context • Integrated with build system Wednesday, October 17, 12
12. Grails plugins in a nutshell • Central public plugin repository • Version management • Dependency management Wednesday, October 17, 12
13. Grails - plugins inside • Many parts of Grails itself are built as plugins • Some default plugins can even be swapped out • Tomcat -> Jetty • GORM/Hibernate -> Redis GORM Wednesday, October 17, 12
14. Public Grails plugins • 850 public plugins in the central plugins repository • Search on plugin portal http://grails.org/plugins/ • Quickly bootstrap new applications • Spend some time now save some time later • Follow @grailsplugins for updates Wednesday, October 17, 12
15. Selected Grails plugins Spring Security - user authentication Cache - caching using annotations Quartz - job scheduling (like cron) DB Migration - controlled schema changes Mail - send email with JavaMail Resources - web performance optimization Console - in-app interactive console CodeNarc - static code analysis Spock - enable Spock unit testing framework Wednesday, October 17, 12
16. What can go into a plugin? • Really, anything • Standard Grails artifacts: GSPs, Controllers, Services, i18n, TagLibs - just like in app • Define custom Grails artifact types: see Quartz plugin “Jobs” • Plugins can depend on other plugins Wednesday, October 17, 12
17. Agenda • Grails plugins overview • Grails plugin development basics • Application architecture with private plugins • Lessons learned Wednesday, October 17, 12
18. Creating a new plugin grails create-plugin myplugin Wednesday, October 17, 12
19. Creating a new plugin Same structure as a Grails application, but with an extra plugin descriptor file Wednesday, October 17, 12
20. Plugin Descriptor class MypluginGrailsPlugin { // the plugin version def version = "0.1" // the version or versions of Grails the plugin is designed for def grailsVersion = "2.1 > *" // the other plugins this plugin depends on def dependsOn = [:] def doWithDynamicMethods = { ctx -> // TODO Implement registering dynamic methods to classes (optional) } def doWithApplicationContext = { applicationContext -> // TODO Implement post initialization spring config (optional) } Wednesday, October 17, 12
21. Excluded plugin files Grails excludes certain files from packaging /grails-app/conf/BootStrap.groovy /grails-app/conf/BuildConfig.groovy /grails-app/conf/Config.groovy /grails-app/conf/DataSource.groovy (and any other *DataSource.groovy) /grails-app/conf/UrlMappings.groovy /grails-app/conf/spring/resources.groovy /web-app/WEB-INF/** /web-app/plugins/** /test/** Wednesday, October 17, 12
22. Running a plugin • A plugin is a Grails app! • grails run-app from plugin dir • excluded files loaded during run-app • useful for testing (test-app works too) Wednesday, October 17, 12
23. Packaging a plugin • grails package-plugin • creates a zip file that can be installed & distributed Wednesday, October 17, 12
24. Installing a plugin from local directory: grails install-plugin /path/to/grails-example-0.1.zip from URL: grails install-plugin http://myserver.com/plugins/grails- example-0.1.zip in BuildConfig.groovy (“in-place” plugin): // Uncomment this only for local development - do not check in! grails.plugin.location.'spectrum-core' = '../spectrum-core' Wednesday, October 17, 12
25. Plugin Development • Easy: create Controllers, Services, Views, Taglibs, etc. • Specify resource paths <g:resource> • Can alter Spring context • Hook into build system, reload events Wednesday, October 17, 12
26. • Grails plugins overview • Grails plugin development basics • Application architecture with private plugins • Lessons learned Agenda Wednesday, October 17, 12
27. Public vs. Private plugins • Highly cohesive • Maximize reuse • Sometimes provide “horizontal slices” - e.g. Spring security core • Most don’t depend on other plugins Public plugins Wednesday, October 17, 12
28. Public vs. Private plugins • Proprietary code • Application or domain-specific • Code reuse within an organization • Can be coarse-grained, heavyweight • Private forks of public plugins • Enable interesting options for application architecture Private Plugins Wednesday, October 17, 12
29. From “big ball of mud” to plugin architecture • Grails applications tend to become unmanageable over time • Convention-based directory trees (e.g. /grails-app/views ) • Rapid development/scaffolding • Need “separation of concerns” Wednesday, October 17, 12
30. From “big ball of mud” to plugin architecture Front End Controllers/Views/ Services (e.g. article, blog pages) Domain classes (e.g Article, BlogPost) CMS Controllers/ Views/Services Quartz Jobs (e.g. sitemap generation) Spectrum Taglib Utility classes (src/**) UrlMappings Test classes Front End & CMS images, CSS, JS Spectrum application before refactoring Wednesday, October 17, 12
31. Reusable domain model • Reuse a set of Domain classes between applications • Different applications, same DB instance • Hibernate not included in plugins by default • Consider Hibernate caching issues DB Primary web application Domain Model plugin API endpoint application Domain Model plugin Reporting application Domain Model plugin Wednesday, October 17, 12
32. Refactored with plugin Front End Controllers/Views Core Domain classes CMS Controllers/ Views/Services Quartz Jobs Front End Taglib Utility classes (src/**) Front End UrlMappings Test classes Front End images, CSS, JS CMS test classes CoreUrlMappings Spectrum Core Plugin Spectrum Application CMS images, CSS, JS Common Front End Controllers Core Services CMS Taglib Depends on other plugins: spring-security-core, quartz, searchable, ckeditor, and others Wednesday, October 17, 12
33. Different web sites, common backend code spectrum-core Plugin Spectrum website 10.4+ The Institute website 3.0 Wednesday, October 17, 12
34. Same Controller, different Views FrontendArticleController#show() Spectrum application show.gsp The Institute application show.gsp Wednesday, October 17, 12
35. Same Controller, different Views • Define common Controller in plugin • View resolution: application first, then plugin • Can specify plugin using <g:render plugin=”myplugin”> • The promise of MVC fulfilled! Wednesday, October 17, 12
36. Plugin UrlMappings • UrlMappings.groovy excluded from plugin build • *UrlMappings.groovy merged into application mappings • Application can override plugin mappings • Enables “mini application” in plugin • Can’t remove unwanted mappings, only override Wednesday, October 17, 12
37. Config.groovy • Config.groovy is excluded from plugin • Might want to fix certain config properties - won’t need them in application Config • Manually merge config in doWithSpring • application.config.merge(new ConfigSlurper().parse(application.classLoader.loadClass('MyPluginConfig '))) Wednesday, October 17, 12
38. Extending plugin domain model Domain classes in plugins can be extended in application Content class Domain model plugin Webinar extends Content Application Wednesday, October 17, 12
39. Publishing private plugins • Publish to internal corporate Maven repo - e.g. Artifactory or Nexus • Release plugin - installed by default • Old-style svn-based repos supported, but not recommended for Grails 2 • Customize plugin metadata with internal Maven groupId • Publish from Jenkins Wednesday, October 17, 12
40. Declaring private plugin dependencies repositories { grailsPlugins() /* other default repos here */ /* point to internal corporate Maven repo */ mavenRepo 'http://mvn.ieee.org/nexus/content/repositories/spectrum/' } plugins { /* other plugin dependencies here */ compile 'org.ieee.spectrum.plugins:spectrum-core:2.0-SNAPSHOT' } BuildConfig.groovy (Maven/Ivy dependencies) Wednesday, October 17, 12
41. Day-to-day development • Use “in-place” plugin (exploded plugin) in your local dev workspace (BuildConfig.groovy) • Private plugins tend to be updated along with application features • Beware of potential breaking changes (in other applications) • Define deprecation strategy and use @deprecated javadoc Wednesday, October 17, 12
42. Refactoring to plugin • Determine candidates for refactoring • Create new empty plugin & plugin descriptor • Move Grails artifacts (e.g. Controllers, Services, Views, etc.) into new plugin • Move dependent files from /src • Move related test files into new plugin • Remove hard coded paths to resources • Run your functional test suite Wednesday, October 17, 12
43. Refactoring to plugin • Start small - don’t create a whole bunch of plugins from the outset • Consider migrating version history Wednesday, October 17, 12
44. Super-project with plugins One application with several in-place plugins /myapplication /grails-app ... /pluginA /grails-app /pluginB /pluginC grails.plugin.location.pluginA = 'pluginA' // path to plugin grails.plugin.location.pluginB = 'pluginB' grails.plugin.location.pluginC = 'pluginC' In BuildConfig.groovy: Wednesday, October 17, 12
45. Public website, private back end Deploy public and private versions of application with shared code DB Business- facing application Core application plugin Public-facing application Core application plugin Public Internet Private intranet Wednesday, October 17, 12
46. Vertical slices / mini Grails applications • Plugins can be self contained • UrlMappings + Controllers + Domains + Views + Services = Grails application • Remove views -> “white label” application • Embed a small application within another application • Vertically slice your application into plugins Wednesday, October 17, 12
47. Plugins as a platform Clinical Data Management Platform plugin Clinical data management server application Clinical data review application Data Capture plugin Data Cleaning plugin Data Validation plugin Super-plugin to combine plugin dependencies into a platform or domain-specific framework Wednesday, October 17, 12
48. Sensitive code protection Data Ingestion plugin Data Analysis plugin “secret sauce” Full application DB Shell application (external team) Split application into separate parts to isolate key algorithms from external vendor Wednesday, October 17, 12
49. • Grails plugins overview • Grails plugin development basics • Application architecture with private plugins • Lessons learned Agenda Wednesday, October 17, 12
50. Domain/Schema management • Changes to domain model need to be carefully managed • Avoid dbCreate=update • Adopt DDL file naming convention: spectrum-core-2.1.sql spectrum-core-2.2.sql • Bootstrap-triggered migrations • DB Migrations plugin (Liquibase) Wednesday, October 17, 12
51. Config.groovy changes over time • Easy to add a new entry to Config.groovy and then forget about it • Group together plugin config properties into a closure • Don’t forget about external config files and differences in various environments Wednesday, October 17, 12
52. Maven/Ivy/build issues • Maven/Ivy hell > JAR hell • SNAPSHOT resolution error-prone • See JIRA for bugs related to plugins • Avoid creating many small plugins • Strange problems? Look at your build. Wednesday, October 17, 12
53. Plugin versioning and branching • Define version numbering strategy • Be prepared to branch/merge • Be sure to update plugin versions and tag your code consistently • Just use Git - merging & cherry- picking are sweet Wednesday, October 17, 12
54. Code Rigidity • Inflexibility to change/afferent coupling • Avoid breaking changes (duh) • Solution: automate your tests, catch breaking changes early Wednesday, October 17, 12
55. Continuous Integration • Use Jenkins to trigger builds of applications that depend on your private plugin • Run Plugin test suite with plugin build • Publish snapshots to Maven repo from Jenkins Wednesday, October 17, 12
56. Plugin namespace conflicts • Plugin artifacts all share same namespace with each other • Potential for class name collisions, especially with “conventions” • Planned enhancement for Grails 2.2 Wednesday, October 17, 12
57. Plugin resources • Plugin static resources (images, CSS, JS, etc.) packaged in a path corresponding to plugin name & version - /plugins/ myplugin-1.0/* • path changes between dev mode and WAR - <g:resource> handles correctly • May need to redeploy with each plugin version bump • Don’t accidentally share sensitive files! Wednesday, October 17, 12
58. Component interfaces • Grails plugins don’t have any kind of external “interface” or contract besides Plugin Metadata • Up to you to make the rules (not a bad thing) Wednesday, October 17, 12
59. Release strategy for 2013 website redesign Success! spectrum-core Plugin 2.0, 2.1, 2.2 Spectrum website 10.8, 10.9, 10.10 The Institute website 3.x Spectrum website 4.0 - 2013 release Wednesday, October 17, 12
60. Takeaway • Plugins are easy to create and use • Private plugins are a safe, robust way to modularize Grails applications • Private plugins enable coarse-grained reuse of application components • Configuration management and OO principles are important (as always) Wednesday, October 17, 12
61. Additional resources • @grailsplugins - Grails plugin updates - https://twitter.com/ grailsplugins • Grails reference docs chapter on plugins - http://grails.org/doc/ latest/guide/plugins.html • Inside Grails: The Build System and Plugin Management - http:// www.slideshare.net/skillsmatter/grails-internals-ggug-dec-2009 • GGUG: Grails Plugins - Lessons to Learn http://skillsmatter.com/ podcast/java-jee/grails-plugins Wednesday, October 17, 12
62. Questions? Wednesday, October 17, 12
63. Thanks! feedback is appreciated. @kenliu k.a.liu@ieee.org Wednesday, October 17, 12