jt400.jar is very cool. I had chatgpt write an application that uses AS400 DTAQs. The AS400 often responds to requests from other application tiers but with DTAQs, it can send a request out to the web. Here, the request would be managed or acted on by additional Kotlin code.

kotlin_and_AS400.kt

import com.ibm.as400.access.AS400
import com.ibm.as400.access.DataQueue
import com.ibm.as400.access.DataQueueEntry
import com.ibm.as400.access.KeyedDataQueue
import java.nio.charset.Charset

fun main() {

    // Connect to IBM i
    val system = AS400(
        "myibmi.company.com",
        "MYUSER",
        "MYPASSWORD"
    )

    // FIFO data queue (source)
    val fifoQueuePath =
        "/QSYS.LIB/MYLIB.LIB/INQUEUE.DTAQ"

    // Keyed data queue (target)
    val keyedQueuePath =
        "/QSYS.LIB/MYLIB.LIB/OUTQUEUE.DTAQ"

    val fifoQueue = DataQueue(system, fifoQueuePath)

    val keyedQueue = KeyedDataQueue(system, keyedQueuePath)

    try {

        println("Waiting for message from FIFO queue...")

        // Blocking read
        val entry: DataQueueEntry = fifoQueue.read()

        val rawData: ByteArray = entry.data

        val message =
            String(rawData, Charset.forName("IBM037")).trim()

        println("Received: $message")

        /*
           Example message format:

           CUST1001|Invoice 44321

           Key = CUST1001
           Payload = Invoice 44321
        */

        val parts = message.split("|")

        if (parts.size < 2) {
            throw IllegalArgumentException(
                "Invalid message format"
            )
        }

        val key = parts[0]
        val payload = parts[1]

        println("Key: $key")
        println("Payload: $payload")

        // Convert key/data to bytes
        val keyBytes =
            key.toByteArray(Charset.forName("IBM037"))

        val payloadBytes =
            payload.toByteArray(Charset.forName("IBM037"))

        // Write to keyed data queue
        keyedQueue.write(
            keyBytes,
            payloadBytes
        )

        println("Message written to keyed queue")

    } finally {

        // Disconnect data queue service
        system.disconnectService(AS400.DATAQUEUE)
    }
}