BOF2644 Developing Java EE 7 Scala apps

Developing Java EE 7
Applications with
Scala (CON2664)
Demystifying the Object-Functional
Peter Pilgrim
Scala and Java EE
Independent contractor
@peter_pilgrim

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Attribution-NonCommercial-ShareAlike 2.0 UK:
England & Wales (CC BY-NC-SA 2.0 UK)
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• Share — copy and redistribute the material in
any medium or format
• Adapt — remix, transform, and build upon the
material
• The licensor cannot revoke these freedoms as
long as you follow the license terms.
Xenonique
2

Xenonique
About Me
• Scala and Java EE developer independent
contractor
• Digital transformation / e-commerce
• Java Champion
• Working on the JVM since 1998
3

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Java EE 7
Developer
Handbook
September
2013
Packt
Publishing
Digital
Java EE 7
Web APPS
December
2014
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5
Agenda
• Scala Technology
• Java EE 7
• CDI
• JSF, Servlets
• JAX-RS, JMS

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#1 Scala
Object-functional
Since 2003
Statically typed programming
Scalable Language
Inventor: Professor Martin Odersky, EPFL, Typesafe

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#1 Scala
Pattern Matching
Case Classes
Traits, Mix-ins, Collections
Expressions, In-fix operators
Functions, Closures, Control Abstractions
Extension through Library functions

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#1 Scala
Gradle, Gradle, Gradle v2.0
Groovy assembler, builder
Comprehensible, Configurable, Flexible
Works with Scala since Gradle v1.7
With Gradle, building WAR files is very straightforward

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Scala Language
var age: Int = 37
val pi: Double = 3.141596527
val text: String = "human nature"
val r = if (age >= 18 ) "Adult" else "Child"
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Scala Test #1
import collection.mutable.Stack
import org.scalatest._
import org.scalatest.junit.JUnitRunner
@RunWith(classOf[JUnitRunner])
class StackSpec extends
FlatSpec with Matchers {
/* ... */
}
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Scala Test #2
class StackSpec extends FlatSpec with Matchers {
"A Stack" should
"pop values in last-in-first-out order" in
{
val stack = new Stack[Int]
stack.push(1)
stack.push(2)
stack.pop() should be (2)
stack.pop() should be (1)
}
/* ... */
}
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Scala Test #3
class StackSpec extends FlatSpec with Matchers {
/* ... */
it should
"throw NoSuchElementException if an empty
stack is popped"
in {
val emptyStack = new Stack[Int]
a [NoSuchElementException]
should be thrownBy {
emptyStack.pop()
}
}
}
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Java is a programming language.
Java is a virtual machine.
Java is a platform.
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14
Java EE 7 released 2013
Built products on top of a standard platform
Transactions, Concurrency, Remote
Endpoints, Lifecycle, State, Persistence

Context & Dependency Injection
• Writing Scala beans
• Annotate with Scala @BeanProperty on
POSI (Plain Old Scala Instances)
• Ensure compatibility with Java code
• @BeanProperty exposes properties to CDI
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Plain Old Scala Instance
@ApplicationScoped
class CashierService
{
@BeanProperty @Inject()
var service: PaymentService = _
def process( acc: Account,
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amount: BigDecimal): Unit = {
service.debit(amount);
acc.balance = acc.balance - amount
}
}
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CDI Dependent Object
@ApplicationScoped
class PaymentService {
var message: String = _
def debit(amount: BigDecimal): Unit = {
message = s"You paid ${amount}"
}
}
// Note String interpolators
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CDI Model instance
class Account(
var balance: BigDecimal
)
// This is a complete class definition! ;-)
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CDI Scala Gotchas
• Companion Objects cannot be used
• Case Classes (and obviously Case Objects)
– Failure due to creation of multiple static methods
in byte code
• Implicit class parameters
• Implicit method parameters
• Lazy public vals also fail
21

Building Java EE 7 War Files
• Gradle allows developers to build WAR files
very easy and also add customisation
• Explicitly include the Scala Library JAR as a
dependency
• With SBT, it is harder to create WAR files
– Battling between *.scala and *.sbt files
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Sample Gradle Dependencies
dependencies {
providedCompile 'javax:javaee-api:7.0’
compile
'org.scala-lang:scala-library:2.11.2'
testCompile 'junit:junit:4.11'
testCompile
'org.scalatest:scalatest_2.11:2.2.0’
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}
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CDI Factory #1
trait Maker {
def createSample(): Fruit
}
@ApplicationScoped
class FruitFactory {
private class CocktailMaker extends Maker {
override def createSample():Fruit = new Strawberry
}
private class FruitSaladMaker extends Maker {
override def createSample():Fruit = new Banana
}
}
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CDI Factory #2
@ApplicationScoped
class FruitFactory {
// ...
@Produces
def generateCocktail(): Maker =
new CocktailMaker()
@Produces
def generateFruitSalad(): Maker =
new FruitSaladMaker()
}
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CDI Factory #3
trait Fruit {
val price: Double;
val name = this.getClass.getSimpleName
}
case class Apple() extends Fruit {
override val price = 0.75 }
case class Banana() extends Fruit {
case class Strawberry() extends Fruit {
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#1 Collection Of Case
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Classes
@ApplicationScoped
class FruitVendor {
def sell( fruit: Fruit with Product with
Serializable, quantity: Int): Double = {
fruit.price * quantity
}
}
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#2 Collection Of Case
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Classes
@Test
def shouldPriceFruitWithQuantity(): Unit = {
val fruits = List((Apple,2), (Orange,4),
(Banana,5))
for ( (fruit, quantity) <- fruits) {
val product =
fruitVendor.sell(fruit(), quantity)
assertEquals(
product, fruit().price * quantity, 0.01 )
}
}
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#3 Collection Of Case Classes
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Sugaring of Supertype
scala> val list = List( Apple -> 1,
Orange -> 4, Banana -> 7 )
list: List[(scala.runtime.AbstractFunction0[
Product with Serializable with Fruit]
with Serializable, Int)]
= List((Apple,1), (Orange,4), (Banana,7))
// [R]AbstractFunction0.apply() => R
// fruit() returns the Fruit mix-in type
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#2 Arquillian:
Prefer integration tests over unit tests.
You can write Arquillian tests with Scala
You cannot yet mix ScalaTest specifications

Writing Arquillian Tests with
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Scala #1
// HERE WOULD BE THE IDEAL WORLD
import org.jboss.arquillian.junit.Arquillian
import org.junit.runner.RunWith
import org.scalatest.junit. JUnitSuite}
import org.scalatest.{FlatSpecLike, Matcher}
@RunWith(classOf[Arquillian],
classOf[JUnitRunner]) /* ;-) */
class HelloArquillianSpec extends JUnitSuite
with FlatSpecLike with Matchers {
}
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Scala #2
// The Reality of the Situation in 2014
@RunWith(classOf[Arquillian])
with Matchers {
// You can’t use BDD like specificationsL
}
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Scala #3
// Add a companion object, generate a WAR file
object HelloArquillianSpec {
@Deployment def createDeployment():WebArchive = {
ShrinkWrap.create(
classOf[WebArchive], "test.war")
.addPackage("uk.co.xenonique.digitalone")
.addAsLibrary( GradleDependency.resolve(
"org.scala-lang:scala-library:2.11.1") )
.addAsLibrary( GradleDependency.resolve(
"org.scalatest:scalatest_2.11:2.2.0") )
.addAsManifestResource(EmptyAsset.INSTANCE,
"beans.xml”)
}
}
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Scala #4
// Add a companion object
@RunWith(classOf[Arquillian])
with Matchers {
@Inject var hello: Hello = _
@Test
def shouldPrintAPoliteGreeting():Unit = {
val msg = hello.hello("JavaOne 2014")
// ;-) At least, we can use matchers!
(msg) should be ("Hello JavaOne 2014")
}
}
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#3
Servlets
A
Java
Servlet
is
a
web
component
managed
container.
Java
Servlets
are
based
on
the
Java
technology,
they
generate
dynamic
content,
and
hence
the
container
that
manages
them
is
capable
of
delivering
dynamic
content
to
the
web
client.

Simplest Json Servlet
@WebServlet(Array("/simple"))
class SimpleServlet extends HttpServlet {
override def doGet(req: HttpServletRequest,
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resp: HttpServletResponse): Unit = {
resp.setContentType("application/json”)
val writer = resp.getWriter()
writer.println(
s"""
|{
| "trackTitle": "Two Tribes",
| "class": "${this.getClass().getName}",
| "date": "${new Date()}"
|}
""".stripMargin )
}
}
36

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37
#4 JAX-RS
Easy to write in Scala
Jackson Annotations, Json4S
We demand Json support with seamless Scala support
Jackson, especially, FasterXML is extremely helpful
https://github.com/FasterXML/jackson-annotations/
For Parsing JSON from text strings, then examine Json4S
https://github.com/json4s/json4s

Convert Posis to Json
// How do we convert this POSI to JSON
// to seamlessly and easily? ;-/
class Traveller(
@BeanProperty var givenName: String,
@BeanProperty var familyName: String,
@BeanProperty var dateOfBirth: Date ,
@BeanProperty var docNo: String )
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Jackson Json Jaxb Annotations
// Look at the Jackson JAX-B project for
// inspiration ;-D
class Traveller2(
@BeanProperty @JsonProperty("givenName")
var givenName: String,
@BeanProperty @JsonProperty("familyName")
var familyName: String,
@BeanProperty @JsonProperty("dateOfBirth")
var dateOfBirth: Date,
@BeanProperty @JsonProperty("documentNo")
var docNo: String )
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Restful Scala JAX-RS Service
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Endpoint
@Path("/traveller")
class TravellerServiceEndpoint {
@GET()
@Produces(Array(MediaType.APPLICATION_JSON))
def retrieve(): Response = {
val cal = Calendar.getInstance()
cal.set(1986, Calendar.MAY, 21)
val dob = cal.getTime
val traveller = new Traveller2("Sam", "Smith",
dob, "1234567890")
Response.ok(traveller).build()
}
}
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Jackson Json Mapping With
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Provider
@Singleton
@Provider
@Consumes(Array(MediaType.APPLICATION_JSON,
"application/*+json", "text/json"))
@Produces(Array(MediaType.APPLICATION_JSON,
"application/*+json", "text/json"))
class JacksonScalaContextResolver extends
JacksonJaxbJsonProvider(JacksonScalaContextResolver.getObjectMapper,
JacksonJaxbJsonProvider.DEFAULT_ANNOTATIONS)
object JacksonScalaContextResolver {
def getObjectMapper: ObjectMapper = {
val mapper = new ObjectMapper with ScalaObjectMapper
mapper.registerModule(new DefaultScalaModule)
mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false)
mapper.setSerializationInclusion(Include.NON_NULL)
mapper
}
}
41

Case Classes Instances and
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Jackson Annotations
@JsonIgnoreProperties(Array("databaseId",
"computedDeliveryDateTime"))
case class Traveller3(
@BeanProperty @JsonProperty("givenName")
var givenName: String,
@BeanProperty @JsonProperty("familyName")
var familyName: String,
@BeanProperty @JsonProperty("dateOfBirth")
var dateOfBirth: Date ,
@BeanProperty @JsonProperty("documentNo")
var docNo: Option[String],
@BeanProperty
var computedDeliveryDateTime: Date = new Date())
42

Consuming of Json to Scala
Case Class Instance #1
@POST()
@Consumes(Array(MediaType.APPLICATION_JSON))
def store( traveller: Traveller3): Response = {
if ( traveller.getDocNo().isEmpty ) {
Response.status(
Response.Status.BAD_REQUEST)
.entity(ErrorMessage("E199",
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"Missing document No"))
.build()
}
else {
Response.ok().build()
}
}
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Case Class #2
case class ErrorMessage(
@JsonProperty("id") var id: String,
@JsonProperty("error") var text: String)
// Renders
// { "id": "E199",
// "error": "Missing document No"
// }
44

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#5 JSF
Easy to write in Scala
Conversational, FlowScoped
RequestScoped, SessionScoped
All types of validation are supported including
BeanValidation just like Java

Conversational Scoped
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Managed Bean
@Named("wizard")
@ConversationScoped
class RegisterDrivingLicense extends
Serializable {
@Inject
var conversation: Conversation = _;
@BeanProperty var title: String = _
@BeanProperty var firstName: String = _
@BeanProperty var lastName: String = _
/* ... */ }
46

Controller Methods
def jumpGettingStarted(): String = {
beginConversation()
"form1?faces-redirect=true"
}
def submitPage1(): String = {
beginConversation()
"form2?faces-redirect=true"
}
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Conversational States
def beginConversation(): Unit =
{
if (conversation.isTransient()) {
conversation.begin()
}
}
def endConversation(): Unit =
{
if (!conversation.isTransient()) {
conversation.end()
}
}
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Finish Conversational Scopes
def submitDeclarationPage(): String = {
endConversation()
if ( !declaration ) {
// The declaration was not signed
cancelApplication()
}
else {
// Here the form is complete
"end?faces-redirect=true"
}
}
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#6 JMS
JMS is straight forward to code with Scala
MDB is essentially an asynchronous EJB
Tricky part is publishing with JMS 2.0!

JMS with CDI Qualifiers #1
class JMSResourceProducer {
@Resource(name = "jms/OrderConnectionFactory")
val orderConnFactory: QueueConnectionFactory = _
@Produces @Order
@Resource(name = "jms/OrderQueue")
val orderQueue: Queue = _
@Produces @Order
def createOrderConnection(): QueueConnection =
orderConnectionFactory.createQueueConnection()
/* ... */
}
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JMS with CDI Qualifiers #2
class JMSResourceProducer {
/* ... */
@Produces @Order
def createOrderSession(
@Order conn:QueueConnection):
QueueSession
= conn.createQueueSession(
true, Session.AUTO_ACKNOWLEDGE)
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}
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#Conclusion(1)
Source code is available now!
https://github.com/peterpilgrim/digital-scala-javaone-
2014

#Conclusion(2)
Scala and Java EE 7 integrate well from
an Object-Oriented point of view
Java EE 8 and Lambda API promise a functional
approach. Java EE 7 annotations work in Scala.
The ability of Jackson annotations and a singleton provider to
seamlessly handle Scala’s case classes is a wonderful addition.
Arquillian almost works completely with ScalaTest.
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#Conclusion(3)
WAR files require the runtime Scala
Library
Decent server configuration using Chef and Puppet
can obviate the bundling of the runtime
Scala allows developers to avoid Java boilerplate
Library writers should prefer to explicitly declare the
return types of functions and methods

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@peter_pilgrim
uk.linkedin.com/in/peterpilgrim2000/

#101 Bonus Information on Scala
A Powerful weapon that requires great responsibility
Great developers can create apps
AM #1: “Interactions and individuals over processes and tools”
Xenonique
58

How to avoid null pointers in
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Scala Programming?
val greeting1: Option[String] =
Some("AOTB14")
val greeting2: Option[String] = None
59

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Pattern Matching
def checker(p : Option[String]): String = {
p match {
case Some(v) => v
case _ => "Unexpected"
}
}
checker(greeting1) // "Hello AOTB14"
checker(greeting2) // "Unspecified"
60

Scala’s generic immutable list
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collection type
val list: List[Int] = List(1,2,3,4)
list.foreach { x => println(x) }
// 1,2,3,4
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Scala’s option behaves like
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collection type #2
greeting1.foreach { x =>
println(s"Work: ${x}" ) }
// Work: Hello AOTB14
greeting2.foreach { x =>
println(s"Work: ${x}" ) }
// *** nothing happens ***
62

Read, Evaluate, Print, Loop
• Scala, Clojure, Groovy, Kotlin, Ceylon, Fantom
All have a interpretative mode
• Java JDK does not (yet) have an official REPL
(However try out javarepl.com online)
• Fingers crossed Project Kulla in JDK 9
http://blog.gmane.org/gmane.comp.java.openjdk.general
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List of Creative Commons (2.0)
photography attributions
https://flic.kr/p/ayqvZp
https://www.flickr.com/photos/throughpaintedeyes/
Ryan Seyeau Follow
1000 Faces of Canada # 0084 - Zombie Walk - Explore!
Shot during the annual Zombie Walk in Ottawa.
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William A. Clark Follow
Measurement
Measure twice, cut once.
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Avi Schwab Follow
Equipment used for measuring planes of crystals
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rosefirerising Follow
Pierre Curie, Piezo-Electroscope
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64

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Tahir Hashmi Follow
Developer Death
10 Programmers and a UX Designer died all of a sudden in a war room situation. They were
apparently working too hard.
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Peter Pilgrim
IMG_1481
European JUG leaders meeting in Devoxx 2013
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UNICEF Ethiopia Follow
Hamer mother and child South Omo Zone, SNNPR
Hamer mother and child South Omo Zone, SNNPR.
©UNICEF Ethiopia/2005/Getachew
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65

https://flic.kr/p/baULpM
N i c o l a Follow
Tree - IMG_1242
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marsmetn tallahassee Follow
IDA .. Integro-Differential Analyzer (Sept., 1952) ...item 2.. Richard Dreyfuss: Technology Has 'Killed Time' -- "In geopolitics, the removal of time is fatal." -- "And
you will give up, the protection of Republican Democracy." (July 19 2010) ...
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Ingmar Zahorsky Follow
Traffic Jam
Accidents are common on the narrow streets going through the mountains of Nepal. When such an accident occurs, traffic is often halted for up to 3-4 hours.
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Greg Beatty Follow
Three Pillars
Nikon D800 16-35MM F4.0
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mari_1008 Follow
traffic jam -B
Date: April,2th
Address: Jiangshu Rd,Shanghai,China.
Around 8:30 AM today, A little accident on YuYuan Rd and JiangSu Rd caused traffic jam.
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66

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Victor1558 Follow
Creative_Photoshop_HD_Wallpapers_laba.ws
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astrangelyisolatedplace Follow
Office test #1. Setup fully functional. A rare 1200 no longer in production. Test run
soundtracked by the only #vinyl in the office; The Sesame Street Soundtrack - a
surprise present by @idinesh #technics #turntable #1200 #ocdv1
via Instagram ift.tt/1hpeUEU
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Steve Corey Follow
Treasure Hunt, a short story (5 images)
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67

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Bömmel Follow
Ice Crystal
Ice is nice
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Called to Serve (suit and tie)
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Paolo Campioni Follow
scala
Scendo (stair case spiral)
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68

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-p Follow
Abstraction I.
From my platycerium. (Guide: Voronoi diagram)
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anthony kelly Follow
big ben
big ben and underground sign
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cobalt123 Follow
All We are Saying... (Thought for a New Year)
Peace Pasta from Annie's, with peas, of course.
Give Peace A Chance
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69

BOF2644 Developing Java EE 7 Scala apps

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BOF2644 Developing Java EE 7 Scala apps