Producing messages with the Java SDK

Last updated: October 17, 2026

Build the canonical envelope with EnvelopeCodec.make, encode it to JSON with EnvelopeCodec.encode, then publish the bytes with your own broker client.

import com.babelqueue.*;
import java.util.Map;

Envelope env = EnvelopeCodec.make(
    "urn:babel:orders:created",
    Map.of("order_id", 1042L, "amount", 99.90),
    "orders",
    null);

String body = EnvelopeCodec.encode(env); // compact UTF-8 JSON
// jedis.rpush("queues:orders", body);
//   /  channel.basicPublish("", "orders", props, body.getBytes(StandardCharsets.UTF_8));

encode produces the canonical schema_version: 1 envelope, with meta.lang set to "java":

{
  "job": "urn:babel:orders:created",
  "trace_id": "7b3f9c2a-e41d-4f88-9b2a-1c0d5e6f7a8b",
  "data": { "order_id": 1042, "amount": 99.90 },
  "meta": { "id": "f1e2d3c4-b5a6-4789-90ab-cdef01234567", "queue": "orders", "lang": "java", "schema_version": 1, "created_at": 1749132727000 },
  "attempts": 0
}

Extension (meta) keys

A make overload takes a Map<String, Object> of your own meta entries:

Envelope env = EnvelopeCodec.make(
    "urn:acme:orders:created",
    Map.of("order_id", 1042L),
    "orders",
    null, // trace id: null starts a new trace
    Map.of("ext", Map.of("acme", Map.of("tier", "gold"))));

make and encode throw BabelQueueException for a key that collides with a core meta key (id, queue, lang, schema_version, created_at) or a forbidden one (timestamp, urn, meta.max_retries, meta.attempts, meta.source, meta.ts). Nothing is silently dropped.

Keep vendor data under a single meta.ext.<vendor> block and use snake_case keys (ADR-0031). The entries are written next to the core meta keys and survive every retry, dead-letter and redrive hop. See Extension keys in the envelope spec.

Next: Consuming messages.