2013 gr8 conf_grails_code_from_the_trenches

Grails Code from the Trenches

Collec3ons.shuffle(dayToDayWork)

Edwin van Nes 1989 dBase / Clipper / FoxPro 1995 Borland Delphi 2000 Java 2, Enterprise Edi3on 2005 PHP, Typo3, Joomla!, … 2011 Groovy & Grails

Direc3ons

•  Weapons of Choice •  AbstractDomain •  Heavy-‐Duty Scaffolding •  Mul3-‐lingualiza3on •  Types & Categories •  Connec3ng an API

Weapons of Choice Specifica3on Google Docs, FogBugz, Balsamiq Mockups, PlantUML, yEd, …

Design similar stuff

Construc3on Grails (dûh!), IntelliJ IDEA, mySQL, SVN -‐> GIT, …

Tes3ng JUnit, Spock, Kiln, …

Deployment Jenkins, Gradle, OSX, Ubuntu, MS Windows, …

Project Skype, Google Hangout, IRIS, …

Weapons of Choice Specifica3on Google Docs, FogBugz, Balsamiq Mockups, yEd, …

Deployment Jenkins, OSX, Ubuntu, MS Windows, …

Tes3ng JUnit, Spock, …

Direc3ons

•  Weapons of Choice •  AbstractDomain •  Heavy-‐Duty Scaffolding •  Mul3-‐lingualiza3on •  Types & Categories •  Connec3ng an API •  Error Abstrac3on in a Plugin

WhatWeDoMost*

Services Frontend Portal

Backend Portal Database Our Clients

Consumers (their clients)

* overly simplified for educa3onal purposes

GR8Tunes

Used here as an example for a typical Backend portal

GR8Tunes

Used here as an example for a typical Backend portal

AbstractDomain

•  Not too Groovy probably •  Add some standard akributes – Some useful 3mestamps –  ‘recentlyUpdated’ boolean for easy highligh3ng

– Each record gets a ‘remarks’ akribute

AbstractDomain.Status

Hibernate filters Plugin •  defaultFilter in Backend

–  Status in [Status.ACTIVE, Status.INACTIVE]

•  defaultFilter in Frontend –  Status == Status.ACTIVE

AbstractDomain.Status

Hibernate filters •  defaultFilter in Backend

–  Status in [Status.ACTIVE, Status.INACTIVE]

•  defaultFilter in Frontend –  Status == Status.ACTIVE

AbstractDomain.Status class DefaultFilters { def sessionFactory def filters = { all(controller:'*', action:'*') { before = { def session = sessionFactory.currentSession if (params.filter_status) {

session.enableFilter('statusFilter').setParameter('status',params.filter_status) } else {

session.enableFilter('defaultFilter') } } } } }

AbstractDomain.change

•  Holds a record of type AbstractDomain

•  Like a “muta3on-‐record” •  i.e. future change to the object •  example: division of responsibility (amongst users)

id version change .tle year

1 5 7 The Bright Side of the Moon 1973

id version change .tle year

7 5 null The Dark Side of the Moon 1973

Should verify (op3mis3c)

Hibernate filter: exclude records that are “change records”

Direc3ons

Heavy-‐Duty Scaffolding

•  Substan3al 3me spent on tailor-‐made scaffolding •  Controllers are always scaffolded – Only specific code for a specific domain is coded

•  Views are scaffolded as a start – Much more likely to manually adjust –  But certainly not for each and every Domain Class

•  Domain Classes can contain seungs to influence rendering during scaffolding

Scaffolded Controllers

•  All Controllers exists as files but are 100% scaffolded unless … class AlbumController {

static scaffold = true }

Scaffolded Controllers

•  All Controllers exists as files but are 100% scaffolded unless … class AlbumController {

static scaffold = true def list (Integer max) { // different implementation of Album.list }

SimpleFlow = true •  Simple states –  List –  Edit

•  Mul3ple ac3ons –  Create –  Cancel –  Save –  SaveAndClose –  SaveAndCreate

SimpleFlow = false •  More states

–  List –  Create –  Edit –  Show

•  Same set of ac3ons –  Create –  Cancel –  Save –  SaveAndClose –  SaveAndCreate

Scaffolded Views

•  Views are most likely to be changed – Order of fields from Domain Class constraints

static constraints = { title (blank:false) artist (blank:false) year (display:true)

change (display:false) }

Scaffolded Views

•  Views are most likely to be changed – Order of fields from Domain Class constraints

static constraints = { title (blank:false) artist (blank:false) year (display:true)

change (display:false) }

Scaffolded Views •  Render more artefacts

_form.gsp = fields used in create / edit _table.gsp = <table> used in list for reuse _panel.gsp = simple <div> for reuse list.csv.gsp = used for formatting exports

<%@ page import="gr8tunes.Album" %> <g:if test="${albumInstance instanceof Album}">

<g:fieldValue bean="${albumInstance}" field="year"/> <g:fieldValue bean="${albumInstance}" field="title"/>

</g:link> </g:if> <g:else> <g:fieldValue bean="${albumInstance}" field="year"/> <g:fieldValue bean="${albumInstance}" field="title"/> </g:else> </p> </div>

</g:if>

_panel.gsp

Scaffolding seungs in Domain Classes class Item extends AbstractDomain {

... static scaffolding = [ simpleFlow: true, inFilter: ['status', 'itemType', 'itemCategory'], inSearch: ['title', 'description'], inSort: ['title', 'itemType', 'artist'] ] ...

Direc3ons

Mul3-‐lingualiza3on •  Transla3on of program code –  aka i18n; that’s in Grails right? –  .proper3es file per ‘group of (Domain) classes’

•  album.proper3es •  messages.proper3es •  abstractDomain.proper3es •  enums.proper3es

•  Transla3on of data (records) –  That’s what we refer to as “m17n”

Mul3-‐lingualiza3on •  Transla3on of program code –  aka i18n; that’s in Grails –  .proper3es file per “group of Domain classes”

•  album.proper3es •  messages.proper3es •  abstractDomain.proper3es •  enums.proper3es

•  Transla3on of objects (records) –  That’s what we refer to as “m17n”

Mul3-‐lingualiza3on

•  System default Language reflects the language of all record in the database

•  Data is op3onally “overlayed” with an M17n record

•  By conven3on –  i.e. if the domain-‐name ends in “M17n” –  Scaffolding renders a different controller –  Scaffolding renders a different view

id .tle year image ar.st_id descrip.on

3 Licensed to Ill 1986 /img/4529ad62}.png 5 The first rap rock LP to top the Billboard album chart

id album_id language_id .tle descrip.on

1 3 7 Licensed to Ill Es ist das erste reine Hip-‐Hop-‐Album, das Platz 1 in den US-‐amerikanischen Billboard-‐Charts erreichte.

2 3 4 Licensed to Ill La canzone raggiunse la seuma posizione nella speciale classifica del ”Billboard Hot 100"

AlbumM17n

Language.isSystem == false

Rela3ons are not overlay / translated (could be a limita3on)

Not overlayed

m17n service Class Album extends AbstractDomain {

def m17nService

private String title ...

public String getTitle() { m17nService.getProperty(this, ‘title’) }

m17n service Class Album extends AbstractDomain {

def m17nService

private String title ...

public String getTitle() { m17nService.getProperty(this, ‘title’) }

The m17nService can figure out: •  If an overlay Class exists (by conven3on) •  What the system language is … Language.findByIsSystem(true) •  What the requested Language is (from Session) •  … or return the un-‐translated … this[title]

NB. Session does not necessarily contain browser locale, users can override this

Direc3ons

Types & Categories •  Types –  Hardcoded –  Used by program-‐code(business-‐logic, rendering etc.)

•  Categories –  Added wherever they could be somewhat useful to a par3cular user

–  Used in the UI for quick filters –  Used in the UI for color-‐coding

Types & Categories

•  Types – Hardcoded – Use by program-‐code (business-‐logic, rendering etc.)

•  Categories – Added wherever they could be somewhat useful to a par3cular user

– Used in the UI for quick filters – Used in the UI for color-‐coding

Types & Categories

•  Types – Hardcoded – Use by program-‐code (business-‐logic, rendering etc.)

•  Categories – Added wherever they could be somewhat useful to a par3cular user

– Used in the UI for quick filters – Used in the UI for color-‐coding

An overview … just for the fun of it

Direc3ons

Now something completely different

Connector for API -‐> Grails

•  Example of calling the Flickr REST API •  Explain my approach to API wrapping

Abstrac3on of an API call

1.  Validate the parameters needed for the par3cular call

2.  Well eh, do the actual API call 3.  Process the response or handle any errors

Abstrac3on of an API call

1.  Validate the parameters needed for the par3cular call

2.  Well eh, do the actual API call 3.  Process the response or handle any errors

void apiCall(method, params) { if (validator(params)) { try { def rsp = doApiCall(method,params) return process(rsp) } catch (Exception ex) { ... } } else { // todo: raise validation exception } }

Params

Validator

Processor

Abstrac3on of an API call // abstracting the whole call handling with closures implemented in individual classes private def apiCall(FlickrApiMethod apiImplementation, def apiModel = {} ) { def params = apiImplementation.paramsClosure def validator = apiImplementation.validatorClosure def processor = apiImplementation.processorClosure if (validator(apiModel())) { try { def rsp = doApiCall(apiImplementation.apiMethod, params(apiModel())) return processor(rsp,apiModel()) } catch (FlickrException ex) { FlickrExceptionHandler.handleApiCallException(ex) } } // TODO: raise validation exception return apiModel() }

Implementa3on class photosGetInfo implements FlickrApiMethod{

// API METHOD static final String apiMethod = 'flickr.photos.getInfo' // VALIDATOR Closure validatorClosure = { FlickrPhoto photo -‐> if (!photo || !photo?.id) { return [validated:false, message:"Required value FlickrPhoto.id missing”] } return [validated:true] } // PARAMS Closure paramsClosure = { FlickrPhoto photo -‐> [photo_id:photo?.id, secret:(photo?.secret ?:'')] } ...

// PROCESSOR Closure processorClosure = { GPathResult response, FlickrPhoto photo -‐> photo.isPublic = (response.photo.visibility.@ispublic?.toString() == '1') photo.secret = response.photo.@secret.toString() photo.serverId = response.photo.@server.toInteger() photo.title = response.photo.title.toString() ...

return photo } ...

... // ERROR CODES Closure errorsClosure = { GPathResult response -‐> if (response.err.@code.toInteger() == 1) { return null } // photo not found // recoverable errors if ([100,105,116].contains(response.err.@code.toInteger())) { return new FlickrServiceApiException(response) } else { return new FlickrServiceSyntaxException(response) } }

We we’re at

•  We’ve got a generic implementa3on of calls •  A Class that implements a par3cular call •  The params back-‐and-‐forth are Groovy •  Now 3e it all together in a Grails-‐like way

Service.getPhotoById(..) class flickrService {

… // abstracting call handling implemented in individual classes private def apiCall(def apiImplementation, def apiModel = {}) { … } // public service methods public FlickrPhoto getPhotoById(Long id) { return apiCall( new photosGetInfo(), {new FlickrPhoto(id:id)} ) as FlickrPhoto }

Well, that’s a Wrap

edwin@ihomer.nl linkedin.com/in/edwinvannes twiker.com/edwinvannes

2013 gr8 conf_grails_code_from_the_trenches

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