groovy and gaelyk - lausanne jug 2011 - guillaume laforge

Groovy updateand Gaelyk,

a lightweight toolkit for Google App Engine

Groovy updateand Gaelyk,

a lightweight toolkit for Google App Engine

Guillaume Laforge / @glaforge

• Groovy Project Manager• Head of Groovy Development

at SpringSource• Initiator of the Grails framework• Founder of the Gaelyk toolkit• Co-author of Groovy in Action• Member of «Les Cast Codeurs» podcast

• Speaker: JavaOne, QCon, JavaZone, Sun TechDays, Devoxx, The Spring Experience, SpringOne2GX, JAX, Dynamic Language World, IJTC, and more...

Agenda

•Past–Groovy 1.6 flashback

•Present–Groovy 1.7 novelties–A few Groovy 1.7.x refinements

•Future–What’s cooking for 1.8 and beyond

But first... some figures...

100000

150000

200000

déc.-07 févr.-08 avr.-08 juin-08 août-08 oct.-08 janv.-09 mars-09 mai-09 juil.-09 sept.-09 nov.-09 janv.-10 mars-10 mai-10 juil.-10

Groovy downloads per monthDownloads Moving Average (year)

100000

150000

200000

100000

150000

200000

Groovy 1.5

100000

150000

200000

Groovy 1.5

100000

150000

200000

Groovy 1.5

G2Oneacquisition

100000

150000

200000

Groovy 1.5

G2Oneacquisition

100000

150000

200000

Groovy 1.5

G2Oneacquisition

Groovy 1.6

100000

150000

200000

Groovy 1.5

G2Oneacquisition

Groovy 1.6

100000

150000

200000

Groovy 1.5

G2Oneacquisition

Groovy 1.6

Groovy 1.7

100000

150000

200000

Groovy 1.5

G2Oneacquisition

Groovy 1.6

Groovy 1.7

looking into the Past

Big highlights of Groovy 1.6

• Greater compile-time and runtime performance• Multiple assignments• Optional return for if/else and try/catch/finally• Java 5 annotation definition• AST Transformations• The Grape module and dependency system• Various Swing related improvements• JMX Builder• Metaprogramming additions• JSR-223 scripting engine built-in• Out-of-the-box OSGi support

Multiple assignement

//multipleassignmentdef(a,b)=[1,2]asserta==1&&b==2

//withtypedvariablesdef(intc,Stringd)=[3,"Hi"]assertc==3&&d=="Hi"

defgeocode(Stringplace){[48.8,2.3]}deflat,lng//assignmenttoexistingvariables(lat,lng)=geocode('Paris')

//classicalvariableswapingexample(a,b)=[b,a]

More optional return

//optionalreturnforifstatements

defm1(){if(true)1else0}assertm1()==1

//optionalreturnfortry/catch/finally

defm2(bool){try{if(bool)thrownewException()

1}catch(any){2}finally{3}}assertm2(true)==2&&m2(false)==1

AST Transformation (1/2)

• Groovy 1.6 introduced AST Transformations–AST: Abstract Syntax Tree

• Ability to change what’s being compiled by the Groovy compiler... at compile time–No runtime impact!–Change the semantics of your programs! Even hijack the

Groovy syntax!–Implementing recurring patterns in your code base–Remove boiler-plate code

• Two kinds: global and local–triggered by annotations

AST Transformations (2/2)

• Transformations introduced in 1.6–@Singleton–@Immutable, @Lazy, @Delegate–@Newify–@Category, @Mixin–@PackageScope–Swing’s @Bindable and @Vetoable–Grape’s own @Grab

@Immutable

• To properly implement immutable classes–No mutations — state musn’t change–Private final fields–Defensive copying of mutable components–Proper equals() / hashCode() / toString()

for comparisons or as keys in maps

@ImmutableclassCoordinates{Doublelat,lng}defc1=newCoordinates(lat:48.8,lng:2.5)

defc2=newCoordinates(48.8,2.5)assertc1==c2

Grab a grape!

• Simple distribution and sharing of Groovy scripts• Dependencies stored locally

–Can even use your own local repositories

@Grab(group='org.mortbay.jetty',

module='jetty‐embedded',

version='6.1.0')

defstartServer(){defsrv=newServer(8080)

defctx=newContext(srv,"/",SESSIONS)

ctx.resourceBase="."

ctx.addServlet(GroovyServlet,"*.groovy")

srv.start()}

into the Present...

• Anonymous Inner Classes and Nested Classes• Annotations anywhere• Grape improvements• Power Asserts• AST Viewer• AST Builder• Customize the Groovy Truth!• Rewrite of the GroovyScriptEngine• Groovy Console improvements• SQL support refinements

AIC and NC

• Anonymous Inner Classes and Nested Classes

AIC and NC

• Anonymous Inner Classes and Nested Classes

For Javacopy’n paste

compatibility

sake :-)

Annonymous Inner Classes

booleancalled=false

Timertimer=newTimer()

timer.schedule(newTimerTask(){

voidrun(){

called=true

sleep100assertcalled

Annonymous Inner Classes

booleancalled=false

Timertimer=newTimer()

timer.schedule(newTimerTask(){

voidrun(){

called=true

sleep100assertcalled

{ called = true } as TimerTask

Nested Classes

classEnvironment{staticclassProductionextendsEnvironment{}

staticclassDevelopmentextendsEnvironment{}

newEnvironment.Production()

Anotations almost anywhere

• You can put annotations–on imports–on packages–on variable declarations

• Examples with @Grab following...

Grape improvements (1/4)

• @Grab on import

@Grab(group='net.sf.json‐lib',

module='json‐lib',version='2.3',classifier='jdk15')importnet.sf.json.groovy.*

assertnewJsonSlurper().parseText(

newJsonGroovyBuilder().json{

book(title:"GroovyinAction",

author:"DierkKönigetal")

}.toString()).book.title=="GroovyinAction"

• Shorter module / artifact / version parameter–Example of an annotation on a variable declaration

@Grab('net.sf.json‐lib:json‐lib:2.3:jdk15')

defbuilder=newnet.sf.json.groovy.JsonGroovyBuilder()

defbooks=builder.books{book(title:"GroovyinAction",author:"DierkKoenig")

}assertbooks.toString()=='{"books":{"book":{"title":"GroovyinAction",'+

'"author":"DierkKoenig"}}}'

• Groovy 1.7 introduced Grab resolver–For when you need to specify a specific repository

for a given dependency

@GrabResolver(name='restlet.org',root='http://maven.restlet.org')

@Grab('org.restlet:org.restlet:1.1.6')

importorg.restlet.Restlet

Power Asserts (1/2)

• Much better assert statement!–Invented and developed in the Spock framework

• Given this script...

defenergy=7200*10**15+1defmass=80defcelerity=300000000

assertenergy==mass*celerity**2

Power Asserts (2/2)

• You’ll get a more comprehensible output

Easier AST Transformations

• AST Transformations are a very powerful feature

• But are still rather hard to develop–Need to know the AST API closely

• To help with authoring your own transformations, we’ve introduced–the AST Viewer in the Groovy Console–the AST Builder

AST Viewer

AST Builder

//AbilitytobuildASTparts

//‐‐>fromaStringnewAstBuilder().buildFromString('''"Hello"'''

//‐‐>fromcodenewAstBuilder().buildFromCode{"Hello"}

//‐‐>fromaspecification

List<ASTNode>nodes=newAstBuilder().buildFromSpec{

block{returnStatement{

constant"Hello"

Customize the Groovy Truth!

• Ability to customize the truth by implementing a boolean asBoolean() method

classPredicate{booleanvaluebooleanasBoolean(){value}

deftruePred=newPredicate(value:true)

deffalsePred=newPredicate(value:false)

asserttruePred&&!falsePred

Groovy 1.7.x changes

• Since Groovy 1.7.0...Groovy 1.7.1, 1.7.2, 1.7.3, 1.7.4, 1.7.5 and 1.7.6 have been released already!

• Here’s what’s new!

• Groovy 1.7.5 even further shrinks the grab resolver definition:

@GrabResolver('http://maven.restlet.org')

@Grab('org.restlet:org.restlet:1.1.6')

importorg.restlet.Restlet

Map improvements (1/2)

//mapauto‐vificationdefm=[:].withDefault{key‐>"Default"}

assertm['z']=="Default"

assertm['a']=="Default"

//defaultsort,sortwithacomparator

m.sort()m.sort({a,b‐>a<=>b}asComparator)

//max{}andmin{}assert[a:1,b:2].max{it.value}.value==2

//beforeMap#withDefault()

defwords="onetwotwothreethreethree".split()

deffreq=[:]

words.each{if(itinfreq)freq[it]+=1elsefreq[it]=1}

//afterMap#withDefault()

defwords="onetwotwothreethreethree".split()

deffreq=[:].withDefault{k‐>0}

words.each{

freq[it]+=1

XML back to String

• Ability to retrieve the XML string from a node from an XmlSlurper GPathResult

defxml="""<books><bookisbn="12345">GroovyinAction</book>

</books>"""defroot=newXmlSlurper().parseText(xml)

defsomeNode=root.bookdefbuilder=newStreamingMarkupBuilder()

assertbuilder.bindNode(someNode).toString()==

"<bookisbn='12345'>GroovyinAction</book>"

Currying improvements

//rightcurryingdefdivide={a,b‐>a/b}

defhalver=divide.rcurry(2)

asserthalver(8)==4//curryingn‐thparameterdefjoinWithSeparator={one,sep,two‐>

one+sep+two}defjoinWithComma=joinWithSeparator.ncurry(1,',')

assertjoinWithComma('a','b')=='a,b'

Date improvements

importstaticjava.util.Calendar.*

//converttocalendardefcal=newDate().toCalendar()

//updateadate(oracalendar)

cal.set(year:cal[YEAR]+1)

cal[MONTH]=MARCH

//createanewdate(oracalendar)fromone

defnextYear=cal.updated(year:cal[YEAR]+1)

New String methods

println"""defmethod(){return'bar'}""".stripIndent()

println"""|defmethod(){|return'bar'|}""".stripMargin('|')

//string"translation"(UNIXtr)

assert'hello'.tr('z‐a','Z‐A')=='HELLO'

assert'HelloWorld!'.tr('a‐z','A')=='HAAAAWAAAA!'

assert'HelloWorld!'.tr('lloo','1234')=='He224W4r2d!'

//capitalizethefirstletter

assert'h'.capitalize()=='H'

assert'hello'.capitalize()=='Hello'

assert'helloworld'.capitalize()=='Helloworld'

//tab/space(un)expansion(UNIXexpandcommand)

assert'1234567\t8\t'.expand()=='12345678'

assert'x'.unexpand()=='x\t'

Map supports isCase()

defm=[a:1,b:2]defval='a'

switch(val){casem:"keyinmap";break

//equivalentto//case{valinm}:...

default:"notinmap"}

(G)String to Enum coercion

enumColor{red,green,blue}

//coercionwithasdefr="red"asColor

//implicitcoercionColorb="blue"

//withGStringstoodefg="${'green'}"asColor

...and beyond!

Groovy 1.8 & beyond

• Still subject to discussion• Always evolving roadmap• Things may change!

What’s cooking?

What we’re working on

• More runtime performance improvements• Closures

–annotation parameterscomposition, memoization, and trampoline

• Native JSON support–builder and parser

• New AST transformations• Gradle build• Modularizing Groovy• Align with JDK 7 / Java 7 / Project Coin• Enhanced DSL support

An example, with Fibonacci

• Known example of worst case performance for Groovy

• Groovy 1.7.5 vs Java–25131ms / 1110ms –22x slower!

• Groovy 1.8-beta-3 vs Java–1871ms / 1110ms–only 68% slower

Optimizations for int

• Currently, the optimizations cover most of native operations on primitive ints–Be careful, your mileage may vary

• To come next–optimizations for doubles–improving array accesses–then other primitives optimizations–and mixed cases of primitives

Closure annotation parameters

• Groovy 1.5 brought Java 5 annotations

• What if... we could go beyond what Java offered?–In 1.7, we can put annotations on packages, imports and

variable declarations–But annotations are still limited in terms of parameters

they allow

• Here comes closure annotation parameters!–Groovy 1.8 will give us the ability to access annotation

with closure parameters at runtime

GContracts

• Closures are already allowed in the Groovy 1.7 Antlr grammar–André Steingreß created GContracts,

a «design by contract» module

//aclassinvariant@Invariant({name.size()>0&&age>ageLimit()})

classPerson{Stringname;intage}

//amethodpre‐condition@Requires({message!=null})voidgreet(Stringmessage){...}

//amethodpost‐condition@Ensures({returnResult%2==0})

intevenResult(){...}

Closure composition

• Functional flavor!

defplus2={it+2}deftimes3={it*3}defcomposed1=plus2<<times3assertcomposed1(3)==11assertcomposed1(4)==plus2(times3(4))

defcomposed2=times3<<plus2assertcomposed2(3)==15assertcomposed2(5)==times3(plus2(5))

//reversecompositionassertcomposed1(3)==(times3>>plus2)(3)

Closure memoization

• Memoization: remember the outcome of previous (ideally side-effect free) invocations

defc={a,b‐>sleep1000;a+b}.memoize()

assertc(1,2)==3//after1000ms

assertc(1,2)==3//returnimmediately

//otherforms://atleast10invocationscached

defcAtLeast={...}.memoizeAtLeast(10)

//atmost10invocationscacheddefcAtMost={...}.memoizeAtMost(10)

//between10and20invocationscached

defcAtLeast={...}.memoizeBetween(10,20)

Closure trampoline

• No more infamous StackOvervlow errors for deeply recursive algorithms–if you use closure trampolines explicitely

deffactfact={intn,BigIntegeraccu‐>

n>1?fact.trampoline(n‐1,n*accu):accu

}.trampoline()

deffactorial={intn‐>fact(n,1G)}

assertfactorial(1)==1assertfactorial(3)==6assertfactorial(1000)==402387260077...

New AST xforms (1/2)

• Many new transformations coming up for removing even more boiler plate code

@Log inject a logger in your classes@Field creates a field in your scripts@PackageScope improvements (methods & fields)@Synchronized providing safer synchronization semantics@InheritConstructor ex. when extending Exception@IndexedProperties JavaBeans indexed property support@AutoClone automatic cloning of your beans@AutoExternalizable automatic externalization of your beans

New AST xforms (2/2)

@ThreadInterrupt makes a script interruptible@TimedInterrupt interrupt after a period of time@ConditionalInterrupt interrupt with a custom condition

@Canonical adds equals, hashCode, toString, ctor- @EqualsAndHashCode just equals and hashCode- @ToString just toString- @TupleConstructor adds a «tuple» constructor

Java 7 / 8 / Project Coin

• Alignment with JDK 7 will come in Groovy 1.9• JSR-292 InvokeDynamic• Simple Closures (8)

• Proposals from Project Coin–Strings in switch (7)–Automatic Resource Management (7)–Improved generics type inference (diamond <>) (7)–Simplified varargs method invocation (7)–Better integral literals (7)–Language support for collections (8?)

Improved DSL support

• GEP-3: an extended command expression DSL–Groovy Extension Proposal #3

• Command expressions–basically top-level statements without parens–combine named and non-named arguments in the mix

•for nicer Domain-Specific Languages–(methodName arguments)*

Before GEP-3

• The idea: extend command-expressions, beyond top-level statements, for chained method calls

• Before

send("Hello").to("Graeme")

check(that:margherita).tastes(good)

sell(100.shares).of(MSFT)

take(2.pills).of(chloroquinine).after(6.hours)

wait(10.minutes).and(execute{})

blend(red,green).of(acrylic)

With GEP-3

• After

send"Hello"to"Graeme"

checkthat:margheritatastesgood

sell100.sharesofMSFT

take2.pillsofchloroquinineafter6.hours

wait10.minutesandexecute{}

blendred,greenofacrylic

With GEP-3

• After

send"Hello"to"Graeme"

sell100.sharesofMSFT

take2.pillsofchloroquinineafter6.hours

wait10.minutesandexecute{}

blendred,greenofacrylic

Less parens& commas

The pattern

• A repetition of–method name–arguments (mix of named and normal)

methodname

parameternamed parameter

Summary

• No need to wait for Java 7, 8, 9...–closures, properties, interpolated strings, extended

annotations, metaprogramming, [YOU NAME IT]...

Summary

Groovy’s still

innovative

since 2003!

Summary

Groovy’s still

innovative

since 2003!

Q and A

CloudComputing

IaaS, PaaS, SaaS

• Software as a Service–Gmail, SalesForce.com

• Platform as a Service–Google App Engine

• Infrastructure as a Service–Amazon EC2

PaaSIaaS

IaaS, PaaS, SaaS

PaaSIaaS

IaaS, PaaS, SaaS

PaaSIaaS

Google App Engine

• Google’s PaaS solution• Run your app on Google’s infrastructure

• Initially just Python supported

• Java supported added too–Sandboxed JVM–Jetty servlet container

• Several JVM-compatible language supported

Key aspects

• You can use most of your usual web frameworks for developping apps on App Engine Java–A WAR file, basically! (an exploded war actually)

– Uploading to the cloud by sending deltas of changes

• No OS image, or software to install– Unlike with Amazon EC2

• All the scaling aspects are handled for you– Database / session replication, load balancing...

• There are quotas, but you need a high traffic application to start being charged–Free to get started

Available services

•Memcache– JCache implementation

– Save on CPU and DB

•URL Fetch– Access remote resources– HttpUrlConnection

•Mail– Support both incoming and

outgoing emails

•Images– Resize, crop, rotate...

•XMPP

– Send / receive Jabber messages (GTalk)

•User– Use Google’s user/

authentication system

– OAuth support

•Cron & Task queues– Schedule tasks at regular

intervals

– Queue units of work

•Blobstore– For storing large content

• And much more...

Limitations

•Not our usual relational database–key / value datastore

•30 seconds request duration limit

• Forbidden to –write on the file system–create threads–use raw sockets–issue system calls–use IO / Swing / etc. directly

•There’s a whitelist of classes allowed

• Number of files and their size are limited

Quotas

Quotas (1/2)

•Bandwidth–1,3M requests/day–1GB/day in/out–6.5 CPU hours/day

•Datastore–10M calls–1GB/day–12GB in / 115GB out–60 CPU hours/day

•Mail–7K calls/day–2K recepients/day–5K emails/day–2K attachments–100MB of attachments

•URL Fetch–657K calls/day–4GB in/out /day

Quotas (2/2)

•XMPP–657K calls/day–4GB data sent/day–657K recepients/day–1MB invitations/day

•Image manipulation–864 calls/day–1GB in / 5GB out–2.5M transforms

•Memcache–8.6M calls/day–10GB in–50GB out

•Task queues–100K calls

Quotas (2/2)

•XMPP–657K calls/day–4GB data sent/day–657K recepients/day–1MB invitations/day

•Image manipulation–864 calls/day–1GB in / 5GB out–2.5M transforms

•Memcache–8.6M calls/day–10GB in–50GB out

•Task queues–100K calls

Outdated figures

The Datastore

The datastore...

•Not your father’s relational database! «NoSQL»

• Distributed key / value store– Based on Google’s «BigTable»

– Schema-less approach

• Supporting– Transactions and partitioning

– Hierarchies through entity groups

• Data access APIs– JPA and JDO

• but adds a big request load time factor

– Direct low-level APIs

...and its «limitations»

• You’re not using SQL–No joins–No database constraints–No aggregation functions (count, avg...)

• In a query, you can only filter on one column for inequality

• Transactions only available in entity groups

• You can only update an entity once in a transaction

Nice dashboard

http://gaelyk.appspot.com

Gaelyk 0.6 released!

• Even a 0.6.1...

• Gaelyk is a lightweight Groovy toolkit on top of the Google App Engine Java SDK

• Gaelyk builds on Groovy’s servlet support–Groovlets: Groovy scripts instead of raw servlets!–Groovy templates: JSP-like template engine–Both allow for a clean separation of views and logic

• Gaelyk provides several enhancements around the GAE Java SDK to make life easier, thanks to Groovy’s dynamic nature

Why Groovy?

• Groovy is a dynamic language for the JVM–very flexible, malleable, expressive and concise syntax–easy to learn for Java developers

•deriving from the Java 5 grammar

–provides powerful APIs to simplify the life of developers•possibility to dynamically enrich existing APIs

–support for Groovlets and its own template engine

First steps...

• Go to http://gaelyk.appspot.com

• Download the template project

• Put your first Groovlet in /WEB-INF/groovy

• And your templates in /WEB-INF/pages

• And you’re ready to go!

• Launch dev_appserver.sh

• Go to http://localhost:8080/

The web.xml

<web-app xmlns="http://java.sun.com/xml/ns/javaee" version="2.5">

<listener> <listener-class>groovyx.gaelyk.GaelykServletContextListener</servl

et-class>

</listener> <servlet> <servlet-name>GroovletServlet</servlet-name>

<servlet-class>groovyx.gaelyk.GaelykServlet</servlet-class>

</servlet> <servlet> <servlet-name>TemplateServlet</servlet-name>

<servlet-class>groovyx.gaelyk.GaelykTemplateServlet</servlet-class>

</servlet>

<servlet-mapping> <servlet-name>GroovletServlet</servlet-name>

<url-pattern>*.groovy</url-pattern>

</servlet-mapping> <servlet-mapping> <servlet-name>TemplateServlet</servlet-name>

<url-pattern>*.gtpl</url-pattern>

</servlet-mapping></web-app>

MVC: Groovlets and templates

Groovlets(controllers)

Templates(views)

Entities(domain)

A groovlet

• Instead of writing full-blown servlets, just write Groovy scripts (aka Groovlets)

def numbers = [1, 2, 3, 4]def now = new Date()

html.html { body { numbers.each { number -> p number } p now }}

A groovlet

• Instead of writing full-blown servlets, just write Groovy scripts (aka Groovlets)

def numbers = [1, 2, 3, 4]def now = new Date()

html.html { body { numbers.each { number -> p number } p now }}

Auto-reloading

A template

<html> <body> <% def message = "Hello World!" print message %> <%= message %> ${message} <ul> <% 3.times { %> <li>${message}</li> <% } %> </ul> </body></html>

A template

<html> <body> <% def message = "Hello World!" print message %> <%= message %> ${message} <ul> <% 3.times { %> <li>${message}</li> <% } %> </ul> </body></html>

Auto-reloading

Shortcuts

•Google services–datastore–blobstore–memcache–capabilities–images–urlFetch–mail–userService / user–defaultQueue / queues–xmpp–namespace

•Variables available–request / response–context / application–sessions–params / headers–out / sout / html–localMode / app.*

•Methods available–include / forward /

redirect–println / print

DEMO88

Groovy sugar!

Sending emails with Gaelyk

mail.send to: 'to@gmail.com', from: 'other@gmail.com', subject: 'Hello World', htmlBody: '<bold>Hello</bold>'

...compared to Java

Properties props = new Properties();

Session session = Session.getDefaultInstance(props, null);

try { Message msg = new MimeMessage(session);

msg.setFrom(new InternetAddress("other@gmail.com", "Admin"));

msg.addRecipient(Message.RecipientType.TO,

new InternetAddress("to@example.com", "Mr. User"));

msg.setSubject("Hello World");

msg.setText("<bold>Hello</bold>");

Transport.send(msg);} catch (AddressException e) {}

} catch (MessagingException e) {}

Accessing the datastore

• Direct interaction with the low-level datastore API

Entity entity = new Entity("person") // subscript notation, like when accessing a mapentity['name'] = "Guillaume Laforge" // normal property access notationentity.age = 32

entity.save() // asyncSave()entity.delete() // asyncDelete()

datastore.withTransaction { // do stuff with your entities // within the transaction}

// use the asynchronous datastore servicedatastore.async.put(entity)

Querying to be improved...

import com.google.appengine.api.datastore.*import static com.google.appengine.api.datastore.FetchOptions.Builder.* // query the scripts stored in the datastoredef query = new Query("savedscript") // sort results by descending order of the creation datequery.addSort("dateCreated", Query.SortDirection.DESCENDING) // filters the entities so as to return only scripts by a certain authorquery.addFilter("author", Query.FilterOperator.EQUAL, params.author)

PreparedQuery preparedQuery = datastore.prepare(query) // return only the first 10 resultsdef entities = preparedQuery.asList( withLimit(10) )

...into something groovier?

def entities = datastore.query { select all from savedscript sort desc by dateCreated where author == params.author limit 10} as List

...into something groovier?

def entities = datastore.query { select all from savedscript sort desc by dateCreated where author == params.author limit 10} as List

Not Yet Implemented!

URL Routing system (1/4)

• You can have friendly URL mappings with the URL routing system

–You’ll have to configure the RouteFilter in web.xml

all "/aboutus", redirect: "/blog/2008/10/20/about-us"

all "/blog/@year/@month/@day/@title", forward: "/blog.groovy?year=@year&month=@month@day=@day@title=@title"

get "/blog/@year/@month/@day", forward: "/blog.groovy?year=@year&month=@month@day=@day"

get "/book/isbn/@isbn", forward: "/book.groovy?isbn=@isbn", validate: { isbn ==~ /\d{9}(\d|X)/ }

• You can also define caching times

–Nice for GAE’s infamous «loading requests»•less critical with GAE SDK 1.4

–ability to reserve 3 instances (billing)–warmup requests

get "/aboutus", cache: 24.hours, forward: "/aboutus.gtpl"

get "/breaking-news", cache: 1.minute, forward: "/news.groovy?last=10"

• Special routes for specifying–incoming emails–jabber messages

email to "/incomingMail.groovy"

jabber to "/incomingXmpp.groovy"

• Namespace awareness: nice for multitenancy• Capability awareness: for graceful degradation

// @cust customer variable could be « acme »post "/@cust/update", forward: "/update.groovy", namespace: { "ns-$cust" }

// different destinations depending on the GAE services status

get "/speakers", forward { to "/speakers.groovy" // default destination // when the datastore is not available to "/unavailable.gtpl" on DATASTORE not ENABLED // show some maintenance is upcoming to "/speakers.groovy?maintenance=true" on DATASTORE \ is SCHEDULED_MAINTENANCE}

Capabilities

• Google App Engine allows you to know the status and availability of the various services–DATASTORE, DATESTORE_WRITE, MEMCACHE...–ENABLED, DISABLED, UNKNOWN,

SCHEDULED_MAINTENANCE–is() and not() methods

if (capabilities[DATASTORE_WRITE].is(ENABLED)) { // write some content in the datastore} else { // otherwise, redirect to some maintenance page}

Task queue API

// access a configured queue using the subscript notationqueues['dailyEmailQueue'] // or using the property access notationqueues.dailyEmailQueue // you can also access the default queue with:queues.defaultdefaultQueue

// add a task to the queuequeue << [ countdownMillis: 1000, url: "/task/dailyEmail", taskName: "sendDailyEmailNewsletter", method: 'PUT', params: [date: '20090914'], payload: content]

Jabber / XMPP support (1/3)

• Sending instant messages

String recipient = "someone@gmail.com" // check if the user is onlineif (xmpp.getPresence(recipient).isAvailable()) { // send the message def status = xmpp.send(to: recipient, body: "Hello, how are you?") // checks the message was successfully // delivered to all the recipients assert status.isSuccessful()}

• Sending instant messages with an XML payload

String recipient = "service@gmail.com" // check if the service is onlineif (xmpp.getPresence(recipient).isAvailable()) { // send the message def status = xmpp.send(to: recipient, xml: { customers { customer(id: 1) { name 'Google' } } }) // checks the message was successfully delivered to the service assert status.isSuccessful()}

• Sending instant messages with an XML payload

String recipient = "service@gmail.com" // check if the service is onlineif (xmpp.getPresence(recipient).isAvailable()) { // send the message def status = xmpp.send(to: recipient, xml: { customers { customer(id: 1) { name 'Google' } } }) // checks the message was successfully delivered to the service assert status.isSuccessful()}

<customers> <customer id=’1’> <name>Google</name>

</customer></customers>

• Receving incoming instant messages–Once you’ve configured a route for jabber messages–Add the inbound message service in appengine-web.xml

def message = xmpp.parseMessage(request)// get the body of the messagemessage.body// get the sender Jabber IDmessage.from// get the list of recipients Jabber IDsmessage.recipients // if the message is an XML document instead of a raw string messageif (message.isXml()) { // get the raw XML message.stanza // get a document parsed with XmlSlurper message.xml}

Memcache service

• Map notation access to the cache

class Country implements Serialzable { String name } def countryFr = new Country(name: 'France') // use the subscript notation to put a country object in the cache

// (you can also use non-string keys)memcache['FR'] = countryFr // check that a key is present in the cacheif ('FR' in memcache) { // use the subscript notation to get an entry from the cache using a key

def countryFromCache = memcache['FR']}

Closure memoization

• Cache the return values for each dinstinct invocation (for a given arguments set)

def countEntities = memcache.memoize { String kind -> datastore.prepare( new Query(kind) ) .countEntities()}

// first calldef totalPics = countEntityes('photos')

// second call, hitting the cachetotalPics = countEntityes('photos')

Blobstore enhancements

• The blobstore allows to store some large content–images, videos, etc.

def blob = ...print blob.filename // contentType, creation, size

// output the content of the blob to the responseblob.serve response

// read the content of the blobblob.withReader { Reader r -> ... }blob.withStream { InputStream is -> ... }

// delete the blobblob.delete()

Images service

• Readable DSL for manipulating images

def blobKey = ...

def image = blobKey.image.transform { resize 1600, 1200 crop 0.1, 0.1, 0.9, 0.9 horizontal flip // vertical flip too rotate 90 feeling lucky // image corrections}

def thumbnail = image.resize(100, 100)

Channel Service

• For Comet-style applications

• Then in the view, in JavaScript...

def token = channel.createChannel('clientID')channel.send 'clientID', 'Hi!'

channel = new goog.appengine.Channel(token);socket = channel.open();socket.onmessage = function(msg) { ... }

Simple plugin system (1/3)

• Gaelyk features a simple plugin system for extending your apps and share commonalities

• A plugin lets you–provide additional groovlets and templates–contribute new URL routes–add new categories–define variables in the binding–override existing binding variables–provide any static content–add new libraries–do any initialization–add before/after request hooks

• A plugin is actually just a zip file!–Basically, just a Gaelyk application, minus...

•the Groovy / Gaelyk / GAE JARs•the web.xml and appengine-web.xml descriptors

–But with a /WEB-INF/plugins/myplugin.groovy descriptor

• A plugin must be referenced in /WEB-INF/plugins.groovy with–install myplugin

•shortcut to /WEB-INF/plugins/myplugin.groovy

• An example plugin descriptor–/WEB-INF/plugins/jsonPlugin.groovy

importnet.sf.json.*importnet.sf.json.groovy.*//addnewvariablesinthebindingbinding{

jsonLibVersion="2.3"//asimplestringvariable

json=newJsonGroovyBuilder()//aninstanceofaclassofa3rd‐partyJAR

}//addnewrouteswiththeusualroutingsystemformat

routes{get"/json",forward:"/json.groovy"

}//installacategoryyou'vedevelopped

categoriesjsonlib.JsonlibCategory

before{req,resp‐>...}//orafter

//anyotherinitializationcodeyou'dneed

Summary

• Easy access to a cloud solution–Deploying Java apps, as easily as you would with PHP

• Familiar to Java folks–Your good old Servlet centric webapps style

• Pretty cheap–You need a high-trafficed website to reach the quotas

• Gaelyk provides a simplified approach to creating Servlet centric webapps in a productive manner–Leveraging Groovy’s servlet / template support and

dynamic capabilities

What’s coming next?

• Expect more sugar around the Datastore–An SQL-like query DSL–Easier relationship management (builder?)

• Perhaps pre-compiled groovlets and templates–Less needed since SDK 1.4

•(reserve 3 hot instances, warmup requests)

• Testing facilities specific to Gaelyk–testing utility class, Spock-specific ones...

• Anything that’ll come up in newer GAE SDK versions

Thanks for your attention!

Guillaume Laforge

Head of Groovy Development

Email: glaforge@gmail.com

Twitter: @glaforge

• References:

• http://gaelyk.appspot.com/

• http://groovy.codehaus.org/

• http://code.google.com/appengine/

Picture credits

Myself http://www.flickr.com/photos/romainguy/783719255/sizes/l/in/photostream/Big hat http://cdn.plussizecostumesupercenter.com/csc_inc/images/items/343x432/47703.jpgRIP http://gipsydan.files.wordpress.com/2009/11/rip.jpgHouse / past: http://www.flickr.com/photos/jasonepowell/3680030831/sizes/o/Present clock: http://www.flickr.com/photos/38629278@N04/3784344944/sizes/o/Future: http://www.flickr.com/photos/befuddledsenses/2904000882/sizes/l/Cooking: http://www.flickr.com/photos/eole/449958332/sizes/l/Snail http://www.freakingnews.com/images/app_images/snail-0.jpgUsein bolt record http://www.phombo.com/sports/usain-bolt-beijing-2008-olympics/17450/full/popular/Fibonacci figure http://cnx.org/content/m22060/latest/graphics1.jpgFibonacci face http://www.robinkelly.co.nz/site/acupil/images/lfib.jpgPuzzle: http://www.everystockphoto.com/photo.php?imageId=263521Light bulb: https://newsline.llnl.gov/retooling/mar/03.28.08_images/lightBulb.pngCheck mark: http://www.lnl.infn.it/~epics/WikiDumps/localhost/600px-symbol_ok.svg.pngPuzzle: http://www.everystockphoto.com/photo.php?imageId=263521Light bulb: https://newsline.llnl.gov/retooling/mar/03.28.08_images/lightBulb.pngGreen leaf: http://www.flickr.com/photos/epsos/3384297473/Trafic light: http://rihancompany.com/var/243/35581-Traffic%20light%20drawing.jpgButt kick: http://www.brentcsutoras.com/wp-content/uploads/2009/12/kick-ass-1.jpgLight bulb: https://newsline.llnl.gov/retooling/mar/03.28.08_images/lightBulb.pngSpeed limit : http://www.morguefile.com/archive/display/18492Warehouse : http://www.morguefile.com/archive/display/85628Check mark: http://www.lnl.infn.it/~epics/WikiDumps/localhost/600px-symbol_ok.svg.pngPuzzle: http://www.everystockphoto.com/photo.php?imageId=263521Light bulb: https://newsline.llnl.gov/retooling/mar/03.28.08_images/lightBulb.pngClouds http://www.morguefile.com/archive/display/627059http://www.morguefile.com/archive/display/625552http://www.morguefile.com/archive/display/629785Duke ok GAE http://weblogs.java.net/blog/felipegaucho/archive/ae_gwt_java.pngPython logo : http://python.org/images/python-logo.gifGaelyc cross with clouds : http://www.morguefile.com/archive/display/37889Speed limit : http://www.morguefile.com/archive/display/18492Warehouse : http://www.morguefile.com/archive/display/85628Snow foot steps : http://www.flickr.com/photos/robinvanmourik/2875929243/Sugar : http://www.flickr.com/photos/ayelie/441101223/sizes/l/Press release: http://www.napleswebdesign.net/wp-content/uploads/2009/06/press_release_11.jpg

groovy and gaelyk - lausanne jug 2011 - guillaume laforge

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