Add javadoc before it's too late.

src/main/scala/Main.scala

@@ -3,6 +3,7 @@ package com.voronind.doublegis.test
 import model.server.TitleCrawlerServer
 
 @main def main(): Unit = {
+	// Start the server.
 	val server = new TitleCrawlerServer()
 	server.listen(8000)
 }

src/main/scala/model/crawler/Crawler.scala

@@ -1,6 +1,15 @@
 package com.voronind.doublegis.test
 package model.crawler
 
+/**
+ * Web crawler base interface.
+ * Crawler is used to scrape the required data from a specified url.
+ */
 trait Crawler {
-
+	/**
+	 * Fetch data from url.
+	 * @param url Target to extract from.
+	 * @return Result data.
+	 */
+	def crawl(url: String): String
 }

src/main/scala/model/crawler/TitleCrawler.scala

@@ -1,6 +1,9 @@
 package com.voronind.doublegis.test
 package model.crawler
 
+/**
+ * A crawler that extracts Http Head Title.
+ */
 class TitleCrawler extends Crawler {
-
+	
 }

src/main/scala/model/handler/Handler.scala

@@ -3,6 +3,17 @@ package model.handler
 
 import com.sun.net.httpserver.HttpExchange
 
+/**
+ * Basic trait for a Http handler that handles http connections to a specific context.
+ */
 trait Handler {
+	/**
+	 * Process incoming connection.
+	 * @param exchange Object used to talk with http server.
+	 */
 	def handle(exchange: HttpExchange): Unit
+}
+
+trait HandlerCompanion {
+	val CONTEXT: String
 }

src/main/scala/model/handler/TitleCrawlerHandler.scala

@@ -5,6 +5,9 @@ import model.lib.StreamUtil
 import com.sun.net.httpserver.{HttpExchange, HttpHandler}
 import java.io.InputStream
 
+/**
+ * Handle Http Title crawling.
+ */
 class TitleCrawlerHandler extends HttpHandler, Handler {
 	override def handle(exchange: HttpExchange): Unit = {
 		log(exchange.getRequestBody)
@@ -12,7 +15,7 @@ class TitleCrawlerHandler extends HttpHandler, Handler {
 	}
 
 	private def log(body: InputStream): Unit = {
-		println(f"${TitleCrawlerHandler.context}%s : Got payload.")
+		println(f"${TitleCrawlerHandler.CONTEXT}%s : Got payload.")
 		StreamUtil.copyStream(body, System.out)
 		println()
 	}
@@ -26,6 +29,6 @@ class TitleCrawlerHandler extends HttpHandler, Handler {
 	}
 }
 
-object TitleCrawlerHandler {
+object TitleCrawlerHandler extends HandlerCompanion {
-	val context = "/crawl_title"
+	override val CONTEXT = "/crawl_title"
 }

src/main/scala/model/lib/StreamUtil.scala

@@ -4,7 +4,15 @@ package model.lib
 import java.io.{InputStream, OutputStream}
 import scala.language.postfixOps
 
+/**
+ * Utils for Java IO streams.
+ */
 object StreamUtil {
+	/**
+	 * Copy one stream into another.
+	 * @param in  Source stream.
+	 * @param out Destination stream.
+	 */
 	def copyStream(in: InputStream, out: OutputStream): Unit = {
 		Iterator
 			.continually(in.read)

src/main/scala/model/server/Server.scala

@@ -1,6 +1,13 @@
 package com.voronind.doublegis.test
 package model.server
 
+/**
+ * Http server.
+ */
 trait Server {
+	/**
+	 * Bind to specified port and listen for inputs.
+	 * @param port Port to bind the server to. Ranged 0-65535. Ports bellow 1024 require privileged access.
+	 */
 	def listen(port: Int): Unit
 }

src/main/scala/model/server/TitleCrawlerServer.scala

@@ -8,7 +8,7 @@ import java.net.InetSocketAddress
 class TitleCrawlerServer extends Server {
 	override def listen(port: Int): Unit = {
 		val server = HttpServer.create(new InetSocketAddress(port), 0)
-		server.createContext(TitleCrawlerHandler.context, new TitleCrawlerHandler())
+		server.createContext(TitleCrawlerHandler.CONTEXT, new TitleCrawlerHandler())
 		server.setExecutor(null)
 
 		server.start()