{"id":63098,"date":"2022-03-22T09:00:27","date_gmt":"2022-03-22T09:00:27","guid":{"rendered":"https:\/\/www.cryptocabaret.com\/?p=63098"},"modified":"2022-03-22T09:00:27","modified_gmt":"2022-03-22T09:00:27","slug":"get-started-with-reactive-programming-with-kotlin-on-quarkus","status":"publish","type":"post","link":"https:\/\/www.cryptocabaret.com\/?p=63098","title":{"rendered":"Get started with reactive programming with Kotlin on Quarkus"},"content":{"rendered":"

Get started with reactive programming with Kotlin on Quarkus<\/span>
\nDaniel Oh<\/a><\/span>
\nTue, 03\/22\/2022 – 03:00<\/span><\/p>\n

\n
Up<\/div>\n
Register<\/a> or Login<\/a> to like.<\/div>\n<\/div>\n
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Moving to the cloud with event-driven architecture raises big concerns for enterprises using multiple programming languages such as Java<\/a>, C#, JavaScript<\/a>, Scala, and Groovy<\/a> to implement business requirements. Because enterprises need to redesign multiple architectures for container deployment separately and put more effort into optimizing production on the cloud, developers often must learn a new programming language in line with the production environment. For example, Java developers have to switch their skill sets to Node.Js to develop lightweight event-front applications.<\/p>\n

Kotlin<\/a> addresses these issues and targets various developers who deploy business applications with multiple programming languages on top of Java Virtual Machine (JVM). Kotlin handles these issues with both imperative and reactive approaches. However, there’s still a hustle to catch up on Kotlin’s new syntax and APIs, especially for Java developers. Luckily, the Quarkus<\/a> Kotlin extension makes it easier for developers to implement Kotlin applications.<\/p>\n<\/p>\n

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Create a new Kotlin project using Quarkus CLI<\/h2>\n

I’ll create a new maven project using the Quarkus command line<\/a> as an example. The following command adds Quarkus extensions to enable RESTEasy Reactive, Jackson, and Kotlin extensions:<\/p>\n

\n$ <\/span>quarkus create app reactive-kotlin-example -x<\/span> kotlin,resteasy-reactive-jackson<\/code><\/span><\/pre>\n
The output should look like this:<\/p>\n
\n
...
[<\/span>SUCCESS]<\/span> ✅ \u00a0quarkus project has been successfully generated in:
\n--><\/span> \/<\/span>Users\/<\/span>danieloh\/<\/span>Downloads\/<\/span>demo\/<\/span>reactive-kotlin-example
\n...<\/div><\/div><\/pre>\n
Next, I’ll use Quarkus Dev Mode, which enables live coding<\/a> to resolve the performance issue in the inner loop development. It simplifies the development workflow from writing code to accessing the endpoint or refreshing a web browser without recompiling and redeploying cycle. Run the following commands:<\/p>\n
\n
$ cd<\/span> reactive-kotlin-example
\n$ quarkus dev<\/div><\/div><\/pre>\n
The output should look like this:<\/p>\n
\n
...
\nINFO \u00a0[<\/span>io.quarkus]<\/span> (<\/span>Quarkus Main Thread)<\/span> Profile dev activated. Live Coding activated.
\nINFO \u00a0[<\/span>io.quarkus]<\/span> (<\/span>Quarkus Main Thread)<\/span> Installed features: [<\/span>cdi, kotlin, resteasy-reactive, resteasy-reactive-jackson, smallrye-context-propagation, vertx]<\/span>

--<\/span>
\nTests paused
\nPress [<\/span>r]<\/span> to resume testing, [<\/span>o]<\/span> Toggle test<\/span> output, [<\/span>:]<\/span> for<\/span> the terminal, [<\/span>h]<\/span> for<\/span> more<\/span> options><\/span><\/div><\/div><\/pre>\n
Make Kotlin behave the Quarkus way<\/h2>\n
Kotiln provides a coroutine to run a block of code concurrently, similar to a thread in Java. The coroutine can be suspended in one thread then resume in another thread. Quarkus enables developers to compose suspending functions.<\/p>\n
Open the ReactiveGreetingResource.kt<\/code> file in src\/main\/kotlin\/org\/acme<\/code> directory to replace the hello()<\/strong> method with the following code:<\/p>\n
\n
@GET
\n@Produces(MediaType.TEXT_PLAIN)
\nsuspend fun hello() = \"Hello RESTEasy Reactive by Kotlin Suspend function\"<\/div><\/div><\/pre>\n
Note: This resource file is generated automatically while you create a new Kotiln project using the Quarkus CLI.<\/p>\n
Make sure to access the RESTful API (\/hello<\/code>) if the new suspend function works in the Quarkus development environment. Execute the following curl<\/code> command line in your local terminal, or you can also access the endpoint URL using a web browser:<\/p>\n
\n&<\/span> curl localhost:8080<\/span>\/<\/span>hello<\/code><\/span><\/pre>\n
The output should look like this:<\/p>\n
\nHello RESTEasy Reactive by Kotlin Suspend function<\/span><\/code><\/span><\/pre>\n
Great! It works well. Now I’ll enable Java’s Context and Dependency Injection (CDI) capability in the Kotlin application.<\/p>\n
Enable CDI injection in the Kotlin application<\/h2>\n
Reflections and annotations in Kotlin are different from how Java initializes properties. It probably causes developers to have an issue (e.g., UninitializedPropertyAccessException<\/strong>). Before enabling CDI injection in code, create a new\u00a0GreetingService.kt<\/code>\u00a0service file in the src\/main\/kotlin\/org\/acme<\/code> directory:<\/p>\n
\n
@ApplicationScoped
\nclass GreetingService {

\n\u00a0 \u00a0 fun greeting(name: String): String {
\n\u00a0 \u00a0 \u00a0 \u00a0 return \"Welcome Kotlin in Quarkus, $name\"
\n\u00a0 \u00a0 }

\n}<\/div><\/div><\/pre>\n
Go back to the ReactiveGreetingResource.kt<\/code> file. Add the following code to use @Inject<\/strong> annotation for adopting Kotlin annotation and reflection by @field: Default<\/strong>:<\/p>\n
\n
@Inject
\n@field: Default
\nlateinit var service: GreetingService

\n@GET
\n@Produces(MediaType.TEXT_PLAIN)
\n@Path(\"\/{name}\")
\nfun greeting(@PathParam(\"name\") name: String): String {
\n\u00a0 \u00a0 return service.greeting(name)
\n}<\/div><\/div><\/pre>\n
Access the new endpoint (\/hello\/{name}<\/strong>) if the CDI injection works. Execute the following curl<\/code> command in the local terminal, or access the endpoint URL using a web browser:<\/p>\n
\n&<\/span> curl localhost:8080<\/span>\/<\/span>hello\/<\/span>Daniel<\/code><\/span><\/pre>\n
The output should look like this:<\/p>\n
\nWelcome Kotlin in<\/span> Quarkus, Daniel<\/code><\/span><\/pre>\n
Wrap up<\/h2>\n
You learned how Quarkus enables developers to keep using Kotlin programming APIs for reactive Java applications. Developers benefit from features such as dev services<\/a> and live coding<\/a>. They also increase the performance for the cloud environment deployment through a native executable<\/a>. In another article, I’ll show how to develop data transaction features using Kotlin with Quarkus.<\/p>\n<\/div>\n
\n
Learn how Quarkus enables developers to keep using Kotlin programming APIs for reactive Java applications.<\/p>\n<\/div>\n
\n
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Image by: <\/span><\/p>\n
Opensource.com. CC BY-SA 4.0<\/p>\n<\/div>\n<\/article>\n<\/div>\n
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Java<\/a><\/div>\n
Cloud<\/a><\/div>\n
Programming<\/a><\/div>\n
Containers<\/a><\/div>\n<\/p><\/div>\n
What to read next<\/div>\n

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Get started with reactive programming with Kotlin on Quarkus Daniel Oh Tue, 03\/22\/2022 – 03:00 Up Register or Login to like. Moving to the cloud with event-driven architecture raises big concerns for enterprises using multiple programming languages such as Java, C#, JavaScript, Scala, and Groovy to implement business requirements. Because enterprises need to redesign multiple […]<\/p>\n","protected":false},"author":1,"featured_media":63099,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[307],"tags":[],"class_list":["post-63098","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-open-source"],"_links":{"self":[{"href":"https:\/\/www.cryptocabaret.com\/index.php?rest_route=\/wp\/v2\/posts\/63098","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.cryptocabaret.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.cryptocabaret.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.cryptocabaret.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.cryptocabaret.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=63098"}],"version-history":[{"count":0,"href":"https:\/\/www.cryptocabaret.com\/index.php?rest_route=\/wp\/v2\/posts\/63098\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.cryptocabaret.com\/index.php?rest_route=\/wp\/v2\/media\/63099"}],"wp:attachment":[{"href":"https:\/\/www.cryptocabaret.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=63098"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.cryptocabaret.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=63098"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.cryptocabaret.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=63098"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}