resonate-basic-ephemeral-world-usage-java

Resonate Basic Ephemeral World Usage — Java

Prerelease note. resonate-sdk-java is published on Maven Central — pin io.resonatehq:resonate-sdk-java:0.1.1 (the only release, confirmed against maven-metadata.xml). The API mirrors the Python SDK and may change before a stable 1.0. Requires Java 21+ — the SDK uses virtual threads, a feature generally available in Java 21; Java 8/11/17 will not work. Every code block here is compile-verified against 0.1.1 with a Java 21 toolchain, and cross-checked against the resonatehq-examples/*-java repos and develop/java.mdx (docs PR #230).

Overview

The ephemeral world is wherever your Java program starts: main(), an HTTP handler, a CLI entry point, a background thread. You use a Resonate instance to register durable functions and invoke them top-level. Once an invocation starts, it crosses into the durable world and Resonate guarantees its completion — retries on failure, resumes after crashes, continues across process restarts.

This skill covers the Client API surface only. The Durable World (Context APIs inside workflow functions) is covered in resonate-basic-durable-world-usage-java.

Install

The build tool pulls the SDK from Maven Central — there is nothing to install separately.

// build.gradle.kts
plugins {
    application // lets you run with ./gradlew run
}
dependencies {
    implementation("io.resonatehq:resonate-sdk-java:0.1.1")
}
java { toolchain { languageVersion = JavaLanguageVersion.of(21) } }
application { mainClass = "io.resonatehq.examples.Main" }

Maven is equivalent — add the dependency to pom.xml (and target Java 21 in the compiler plugin):

<dependency>
    <groupId>io.resonatehq</groupId>
    <artifactId>resonate-sdk-java</artifactId>
    <version>0.1.1</version>
</dependency>

Run a program with ./gradlew run (Gradle) or mvn compile exec:java -Dexec.mainClass=... (Maven). A one-shot program exits when main returns; a worker blocks on a CountDownLatch (see Resonate.stop).