Apache Camel - JSLT - Merge objects

JsltExample.kt

package com.example.colector.datasource

import org.apache.camel.builder.RouteBuilder
import org.springframework.stereotype.Component

@Component
class JsltExample : RouteBuilder() {

    override fun configure() {
        from("timer:?repeatCount=1")
            .routeId("jsltExample")
            .removeHeaders("*")
            .process {
                it.message.body = """{"id":1,"description":"Test"}"""
            }
            .setHeader("additional", constant("extra1"))
            .setHeader("additional2", constant("extra2"))
            .to("jslt:file:test.jslt")
            .log("\${body}")
    }
}

result.txt

{"id":1,"description":"Test","additional":"extra1","additional2":"extra2"}

test.jslt

{ for ($headers) .key : .value } +
{ * : . }