Kotlin DSL and Script Enging Example

A simple project influenced by 12 days of Kotlin - Day 02 that shows

1. How can you build DSL with kotlin syntax sugar
2. How can you make that DSL a JSON-like.

Setup

dependencies {
    implementation(kotlin("scripting-jsr223-embeddable"))
}

DSL sugar

In short: trailing lambda, infix, unaryPlus.

All this operations just to drop brackets! But it is sufficient enough to build readable definitions.

sandwich {
   with type "toasted"
   bread = "baguette"
   
   fillings {
       +"cheese"
       +"ham"
   }
}

/!\ Hint: if you override String.unaryPlus() inside Sandwich class, you will have access to all its members.

Transferable DSL (JSON-like)

In short: Tried to answer a question: Can you replace JSON with DSL?

Pros: it is feasible to do following and s would be proper Sandwich object:

with(ScriptEngineManager().getEngineByExtension("kts")) {
        val s = eval(
            """import kon.*
sandwich {
    with type "toasted"
    bread = "baguette"
    
    fillings {
        +"cheese"
        +"ham"
    }
    """)
    }

Cons:

• Extra line of imports (could be auto-added)
• Obviously Not secure: the eval() would execute anything, no checks, no restrictions
• if to be used on Android, would require heavyweight compiler-as-a-library.