As a Java developper, you may be looking for new ways to improve your productivity. If one of the answer was to adopt another language for the JVM? Like Kotlin? Let's see what is Kotlin, why is it a good choice and how you can use it in Liferay 7/DXP.

1. Boost up
your productivity
with Kotlin
Liferay Symposium 2018
Louis-Guillaume Durand

2. Summary
● What is Kotlin?
● Why Kotlin?
● How to use Kotlin in Liferay?

3. What is Kotlin?

4. What is Kotlin?
● Programming language for JVM and JS
● Statically typed
● Open source
● Created by JetBrains (→ IntelliJ IDEA)

5. What is Kotlin?
2010 2011 2016 2017
Project Kotlin JVM Language
Summit
Release 1.0 Android support
{ WORKING }
Release 1.1
Release 1.2

6. What is Kotlin?
JetBrains concerns:
● To be more productive
● Other languages have features or speed, but not both
● To drive the sales of IntelliJ IDEA

7. Why Kotlin?

8. Why Kotlin?
public class HelloWorld {
public static void main(String[] args) {
System.out.println("Hello, world!");
}
}

9. Why Kotlin?
fun main(args: Array<String>) {
println("Hello, world!")
}

10. Why Kotlin?
data class Greeting(val name: String)
fun main(args: Array<String>) {
val greeting = Greeting("world")
println("Hello, ${greeting.name}!")
}

11. Why Kotlin?
data class Greeting(var name: String = "") {
fun sayHello() = println("Hello, $name!")
}
fun main(args: Array<String>) {
val greeting = Greeting()
greeting.name = "world"
greeting.sayHello()
}

12. Why Kotlin?
val greeting: Greeting? = getNullableGreeting()
greeting.name // compilation error
greeting?.name // returns null
greeting!!.name // throws exception

13. Why Kotlin?
class Name(val value: String) {
operator fun plus(name: Name) {
return Name("${this.value} ${name.value}")
}
}

14. Why Kotlin?
val firstName = Name("John")
val lastName = Name("Doe")
val fullName = firstName.plus(lastName)
println(fullName.value) // prints "John Doe"

15. Why Kotlin?
@Deprecated(
level = DeprecationLevel.WARNING, // ERROR, HIDDEN
message = "We use anotherMethod() now",
replaceWith = ReplaceWith("anotherMethod()")
)
fun someMethod()
fun anotherMethod()

16. Why Kotlin?
fun someMethodToImplement() {
TODO("Implement this ASAP")
}
// add TODO and throws exception

17. Why Kotlin?
import org.junit.Assert.assertTrue
import org.junit.Test
class DummyTests {
@Test fun `Ceci n'est pas un test`() {
assertTrue(true)
}
}

18. Why Kotlin?
public class HelloWorld {
public static void printHelloFromJava() {
System.out.println("Hello, world!");
}
}
// ---
fun main(args: Array<String>) {
HelloWorld.printHelloFromJava()
}

19. How to use Kotlin in Liferay?

20. How to use Kotlin in Liferay?
buildscript {
dependencies {
classpath group: "org.jetbrains.kotlin",
name: "kotlin-gradle-plugin",
version: "1.1.2"
}
}
apply plugin: 'kotlin'

21. How to use Kotlin in Liferay?
dependencies {
compileOnly group: "org.jetbrains.kotlin",
name: "kotlin-osgi-bundle",
version: "1.1.2"
}

22. How to use Kotlin in Liferay?
Import-Package:
!kotlin.*,
*
Conditional-Package:
kotlin.*
→ Add an import statement for a
package that is not referred to by your
code but is still needed
→ Recursively add packages from the
class path when referred and when they
match one of the package
specifications

23. How to use Kotlin in Liferay?
@Component(
immediate = true,
property = arrayOf(
"com.liferay.portlet.instanceable=true"
// and much more...
),
service = arrayOf(Portlet::class)
)
class KotlinGreeterPortlet : MVCPortlet() { // ... }

24. How to use Kotlin in Liferay?
class KotlinGreeterPortlet : MVCPortlet() {
@Throws(IOException::class, PortletException::class)
override fun doView(
renderRequest: RenderRequest,
renderResponse: RenderResponse) {
// do awesome stuff with Kotlin...
}
}

25. How to use Kotlin in Liferay?
https://github.com/liferay/liferay-blade-samples

26. Conclusion
● Harder
● Better
● Faster
● Stronger
● An introduction to Kotlin by
example, Dmitry Kandalov
● 10 Kotlin Tricks in 10 ish minutes,
Jake Wharton
● Kotlin in Action, Dmitry Jemerov,
Svetlana Isakova

27. Questions?

28. Thank you :^)