Solon Flow: Lightweight Process Orchestration Without BPMN XML

When you need process orchestration — approval workflows, business rules, data pipelines — the usual answer is a heavyweight engine: BPMN 2.0 XML, database schemas, a management UI, and a framework that drags in half of enterprise Java. Solon Flow takes a different approach. It's a ~200KB engine that treats process definitions as flat YAML or JSON, runs without a database, and lets you resume interrupted processes from a JSON snapshot. You can embed it in any JVM framework — Solon, Spring Boot, Quarkus, or even a plain main() method. This article walks through the core API, node types, context persistence, and driver customization — all verified against the official documentation at solon.noear.org . Getting Started Add the dependency: <dependency> <groupId> org.noear </groupId> <artifactId> solon-flow </artifactId> </dependency> Define a flow in YAML ( flow/demo1.yml ): id : " c1" layout : - { id : " n1" , type : " start" , link : " n2" } - { id : " n2" , type : " activity" , link : " n3" , task : ' System.out.println("hello world!");' } - { id : " n3" , type : " end" } Load and execute: FlowEngine engine = FlowEngine . newInstance (); engine . load ( "classpath:flow/demo1.yml" ); engine . eval ( "c1" ); That's it. No database, no XML schema, no deployment step. In a Solon application, you can inject the engine directly and let it auto-load flow definitions: solon.flow : - " classpath:flow/*.yml" @Component public class DemoCom implements LifecycleBean { @Inject private FlowEngine flowEngine ; @Override public void start () throws Throwable { flowEngine . eval ( "c1" ); } } The engine scans all matching files on startup, so adding a new flow is just dropping a YAML file. Node Types Solon Flow supports seven node types via the NodeType enum: Type Description Task Condition Parallel In Out start Entry point — — — 0 1 activity Default node Yes — — 1..n 1..n exclusive Exclusive gateway (if/else) Yes Yes — 1..n 1..n inclusive Inclusive gateway (multi-select) Yes Yes — 1