Resonate Human-in-the-Loop Pattern — Java

Prerelease note. resonate-sdk-java is published on Maven Central — pin io.resonatehq:resonate-sdk-java:0.1.1. The API mirrors the Python SDK and may change before a stable 1.0. Requires Java 21+ (virtual threads, a feature generally available in Java 21). There is no Java HITL example repo yet, so every code block here uses only documented SDK surface, compile-verified against 0.1.1 and cross-checked against develop/java.mdx (docs PR #230) and the SDK source.

Overview

For the language-agnostic mental model, start with resonate-human-in-the-loop-pattern-typescript. The idea is identical: create a latent durable promise, hand its ID to the external actor who will settle it, and await — the workflow parks until settlement arrives, surviving any number of crashes or restarts.

Resolution from Java is direct. The Java SDK ships a top-level r.promises sub-client (it mirrors Python), so settling a promise from outside the workflow is r.promises.resolve(id, new Value(...)). There is no manual base64 encoding — that extra step is a Go-specific workaround for a sub-client Go lacks. Don't copy it into Java.

When to use

• Approval gates (budget, deploy, content moderation)
• Third-party webhook callbacks (Stripe, DocuSign, Twilio)
• Operator unblock steps in runbooks
• Any step where the decision or data originates outside the Resonate worker set

Basic shape