{"id":692,"date":"2017-05-23T09:57:31","date_gmt":"2017-05-23T09:57:31","guid":{"rendered":"http:\/\/smartfoxserver.com\/blog\/?p=692"},"modified":"2017-05-23T10:05:46","modified_gmt":"2017-05-23T10:05:46","slug":"kotlin-and-smartfoxserver-2x","status":"publish","type":"post","link":"https:\/\/smartfoxserver.com\/blog\/kotlin-and-smartfoxserver-2x\/","title":{"rendered":"Kotlin and SmartFoxServer 2X"},"content":{"rendered":"

You may have heard of the Kotlin<\/a> language before, but recently it has seen a big spike in popularity thanks to Google officially adopting it\u00a0for Android development, alongside Java and C++.<\/p>\n

Kotlin is an interesting statically typed language, developed by the good folks at Jetbrains<\/a>,\u00a0that shares many similarities with the likes of Scala and Swift.\u00a0In a sense, it could be thought of the equivalent of Swift for the Java platform: a more modern, concise and safer language that runs in the JVM, fully interoperable with Java.<\/p>\n

If that’s not enough, Kotlin also aims at compiling for other\u00a0targets beyond the JVM, such as Javascript and native platforms and seeks to support\u00a0asynchronous programming\u00a0via coroutines and non blocking I\/O.<\/p>\n

In the context of using Kotlin with SmartFoxServer<\/strong> nothing would be easier: the integration on both server side and client side is painless and it works out of the box with any SFS2X release.<\/p>\n

Let’s take a closer look, shall we?<\/p>\n

\u00bb Server side<\/h2>\n

So what does it take exactly to write a server side Extension with Kotlin? The easiest way to do it is via Jetbrain’s IntelliJ<\/a>, a commercial multi-language IDE that also comes as a “Community Edition”, free of charge.<\/p>\n

This is very good news for anyone interested in experimenting with Kotlin; so we downloaded a copy, created a new Kotlin Project and added the basic jar files (sfs2x.jar, sfs2x-core.jar) to it.<\/p>\n

\"setting<\/a><\/p>\n

This is done by right-clicking the project name \u00bb Open Module Settings \u00bb Libraries. From there you can click the plus sign (+) at the top of the second column and navigate to your\u00a0jar files folder (i.e. SFS2X\/lib\/).<\/p>\n

Nothing new up to this point besides maybe learning how to use IntelliJ, if you’re not familiar with it. Next comes the interesting part: writing some actual Kotlin code.<\/p>\n

\r\npackage sfs2x.kt\r\n\r\nimport com.smartfoxserver.v2.core.ISFSEvent\r\nimport com.smartfoxserver.v2.core.SFSEventType\r\nimport com.smartfoxserver.v2.extensions.BaseServerEventHandler\r\nimport com.smartfoxserver.v2.extensions.SFSExtension\r\n\r\nclass EventHandler : BaseServerEventHandler()\r\n{\r\n    override fun handleServerEvent(event: ISFSEvent?)\r\n    {\r\n        trace("Event received >> " + event?.type)\r\n    }\r\n}\r\n\r\nclass KotlinTestExtension : SFSExtension()\r\n{\r\n    override  fun init()\r\n    {\r\n        trace("Kotlin Extension running in Zone: " + parentZone.toString())\r\n\r\n        \/\/ Add server event handler\r\n        addEventHandler(SFSEventType.SERVER_READY, EventHandler())\r\n    }\r\n\r\n    override fun destroy()\r\n    {\r\n        super.destroy()\r\n\r\n        trace("Extension shutting down");\r\n    }\r\n}\r\n<\/pre>\n
At the top we have our standard package declaration, just like in Java. Next a few imports and finally we\u00a0encounter the first new concept: multiple classes in the same file!
\nKotlin, as many recent languages, doesn’t force you in the Java’s one-class-per-file philosophy, so we can put two (or more) package\u00a0level classes in the same source file.<\/p>\n
Our main Extension class, KotlinTestExtension<\/strong>, extends the base SFSExtension<\/strong> class using the colon (:) notation, like in C#\/C++. Then we proceed with overriding the init()<\/strong> and destroy() <\/strong>methods, declared with the Kotlin fun<\/strong> keyword, short for function<\/em>\u00a0of course.<\/p>\n
Notice how the Java\u00a0getParentZone()<\/strong>\u00a0Extension method becomes parentZone<\/strong>\u00a0(no method invocation): this is because in Kotlin there are no getters and setters, but only properties<\/a>. This in turn means that all java beans exposed in SFS2X SDK will auto-complete to their property names, rather than their getter\/setter names.<\/p>\n
Also note how instantiating the EventHandler class does not require the “new” keyword, akin to languages such as Python.<\/p>\n
Another bit worth of notice is\u00a0this line\u00a0from the EventHandler<\/strong> class:<\/p>\n
\r\ntrace("Event received >> " + event?.type)\r\n<\/pre>\n
If you’re familiar with languages such as Groovy or Swift you’ll recognize it as the null safe operator<\/a>, which is exactly what this is. A useful compile-time help to avoid those nasty null pointer exceptions.<\/p>\n
Finally we can generate our jar file\u00a0and deploy it to SmartFoxServer. \u00a0To do so, let’s open the Module settings again via right-clicking the project name \u00bb Open Module Settings \u00bb Artifacts.<\/p>\n
\"kot-ext-deploy\"<\/a><\/p>\n
Here we can choose the name and path where we want to deploy the jar file and also include\/exclude specific libraries packaged with\u00a0the jar. This is important because by default IntelliJ will include the two SFS2X libraries we’ve added as part of the final jar.<\/p>\n
We don’t want this<\/strong>,\u00a0<\/strong>because those libraries are already part of the SFS2X runtime and we just use them as dependencies but\u00a0we don’t need them included in our final jar. Make sure to select and remove sfs2x.jar and sfs2x-core.jar from the list, apply the changes and finally we\u00a0can hit the Build \u00bb Build artifacts<\/strong> option to deploy the code.<\/p>\n
Finally we can open the SFS2X AdminTool, navigate to the Zone Configurator, add the Extension to our Zone of choice and voil\u00e0.<\/p>\n
\u00bb Next steps and resources<\/h2>\n
To learn more about Kotlin and its capabilities we highly recommend several interesting resources:<\/p>\n