Kotlin Web Scraping: Complete Guide
Why Use Kotlin for Web Scraping?
Kotlin is a modern programming language that runs on the Java Virtual Machine (JVM). Here are some reasons why Kotlin is a great choice for web scraping:
- Concise Syntax: Kotlin has a more readable and concise syntax compared to Java, making it easier to write and maintain web scraping scripts.
- Interoperability with Java: Kotlin can use Java libraries, allowing you to leverage existing web scraping tools and frameworks.
- Type Safety: Kotlin reduces runtime errors by enforcing type safety, leading to more reliable web scraping scripts.
- Asynchronous Support: Kotlin supports coroutines, which help manage multiple web scraping tasks efficiently.
The Best Alternative to Web Scraping With Kotlin
While Kotlin is a powerful language for web scraping, building and maintaining your own scraper can be complex and time-consuming. Websites frequently update their structures, implement anti-scraping measures, and require handling CAPTCHAs or JavaScript rendering — challenges that demand constant maintenance.
A better alternative is using dedicated web scraping tools and APIs. These solutions provide:
- Faster Deployment: No need to write and debug custom scrapers.
- Scalability: Easily scrape large volumes of data without infrastructure concerns.
- Built-in Anti-Bot Solutions: Overcome restrictions and access data reliably.
- Structured Data Output: Get clean, ready-to-use data in JSON, CSV, or API formats.
If you need a hassle-free, scalable, and efficient way to extract web data, consider using a web scraping platform instead of coding your own solution in Kotlin. Continue
Prerequisites
Before you start web scraping with Kotlin, ensure you have the following installed:
- JDK (Java Development Kit): Install the latest LTS version of JDK.
- Gradle or Maven: A build tool to manage dependencies.
- Kotlin IDE: IntelliJ IDEA or Visual Studio Code with the Kotlin extension.
- Skrape{it} Library: A powerful Kotlin library for web scraping.
Installing Dependencies
To add Skrape{it} to your Kotlin project, open your build.gradle.kts file and add the following dependency:
implementation("it.skrape:skrapeit:1.2.2")
Then, run the following command to install the dependencies:
./gradlew build
Setting Up a Kotlin Web Scraping Project
To create a new Kotlin project, follow these steps:
Open your terminal and create a new directory:
mkdir KotlinWebScraper
cd KotlinWebScraper
- Initialize a new Kotlin project with Gradle:
gradle init — type kotlin-application - Open the project in your Kotlin IDE.
Basic Web Scraping in Kotlin
Let’s write a simple script to scrape an e-commerce site and extract product information.
Step 1: Fetch the Web Page
Import the required packages in App.kt:
import it.skrape.core.*
import it.skrape.fetcher.*
Then, use Skrape{it} to fetch the HTML content of a webpage:
val html: String = skrape(HttpFetcher) {
request {
url = "https://www.scrapingcourse.com/ecommerce/"
}
response {
htmlDocument {
html
}
}
}
println(html)
Step 2: Extract Data
Define a data class to store product details:
data class Product(
var url: String = "",
var image: String = "",
var name: String = "",
var price: String = ""
)
Extract product details using Skrape{it}:
val products: List = skrape(HttpFetcher) {
request {
url = "https://www.scrapingcourse.com/ecommerce/"
}
extractIt<ArrayList> {
htmlDocument {
"li.product" {
findAll {
forEach { productHtmlElement ->
val product = Product(
url = productHtmlElement.a { findFirst { attribute("href") } },
image = productHtmlElement.img { findFirst { attribute("src") } },
name = productHtmlElement.h2 { findFirst { text } },
price = productHtmlElement.span { findFirst { text } }
)
it.add(product)
}
}
}
}
}
}
println(products)
Step 3: Store Data in CSV
Save the extracted data to a CSV file:
import org.apache.commons.csv.CSVFormat
import java.io.FileWriter
val csvFile = FileWriter("products.csv")
CSVFormat.DEFAULT.print(csvFile).apply {
printRecord("url", "image", "name", "price")
products.forEach { (url, image, name, price) ->
printRecord(url, image, name, price)
}
}.close()
csvFile.close()
Advanced Web Scraping Techniques
Web Crawling: Scrape Multiple Pages
Modify your script to scrape multiple pages:
val pagesToScrape = mutableListOf("https://www.scrapingcourse.com/ecommerce/page/1/")
val pagesDiscovered = mutableSetOf()
while (pagesToScrape.isNotEmpty()) {
val pageURL = pagesToScrape.removeAt(0)
skrape(HttpFetcher) {
request { url = pageURL }
response {
htmlDocument {
"a.page-numbers" {
findAll {
forEach { paginationElement ->
val newPage = paginationElement.attribute("href")
if (!pagesDiscovered.contains(newPage)) {
pagesToScrape.add(newPage)
pagesDiscovered.add(newPage)
}
}
}
}
}
}
}
}
Using a Headless Browser
Some websites require JavaScript rendering. Use BrowserFetcher to scrape dynamic sites:
val products: List = skrape(BrowserFetcher) {
request {
url = "https://scrapingclub.com/exercise/list_infinite_scroll/"
}
extractIt<ArrayList> {
htmlDocument {
".post" {
findAll {
forEach { productHtmlElement ->
val product = Product(
url = productHtmlElement.a { findFirst { attribute("href") } },
image = productHtmlElement.img { findFirst { attribute("src") } },
name = productHtmlElement.h4 { findFirst { text } },
price = productHtmlElement.h5 { findFirst { text } }
)
it.add(product)
}
}
}
}
}
}
Discover the best headless browsers to use.
Conclusion
Kotlin is a powerful and modern language for web scraping. With Skrape{it}, you can efficiently fetch, parse, and store web data. Whether you are scraping static or dynamic pages, Kotlin offers flexibility and efficiency in your web scraping projects.
