Advanced DSL: Creating an HTML Builder
3 min readJul 19, 2023
Kotlin domain-specific languages (DSLs) are powerful tools that enable developers to design custom languages for specific tasks. One of the most compelling use-cases of Kotlin DSLs is crafting an HTML builder. It may sound challenging, but it’s incredibly fascinating and rewarding once you get the hang of it.
As American programmer Alan Perlis once said:
“A language that doesn’t affect the way you think about programming is not worth knowing.”
And that’s precisely why we should explore the potentials of Kotlin DSLs, such as creating an HTML builder, which will broaden our perspective on programming.
Starting Simple: HTML Tags
First things first, let’s create the fundamental building blocks of our HTML builder — HTML tags.
Here is a basic example:
// Define a Tag class
open class Tag(val name: String) {
// The children of this tag
val children = mutableListOf<Tag>()
// Generate the HTML for this tag
fun render() = "<$name>${children.joinToString("") { it.render() }}</$name>"
}
// Define an HTML tag
class HTML : Tag("html")In the example above:
Tagis the base class for all our HTML tags. Each tag has a name and a list of child tags.HTMLis a subclass ofTag, representing an<html>tag.render()is a function that generates the HTML for a tag.
