Say Goodbye to If‑Else Nightmares with Flow Orchestration

Configure Flow Execution Chain

Different membership product transaction processes require distinct flow chains. The class DemoMemberPurchaseExtension implements a purchase extension point and defines three flow‑chain configurations, as shown in the screenshot.

Define Flow Nodes

Each flow node provides four methods: process, success, rollback, and callback. The diagram illustrates how these methods are declared.

Flow Execution

To run a flow, provide a context object and call FlowChain.execute. The engine links the nodes and executes them sequentially, following a responsibility‑chain pattern.

The execution order is:

Invoke each node's process method in order.

If a process throws an exception, invoke rollback on already‑executed nodes in reverse order.

If all process calls succeed, invoke success on nodes in reverse order.

Finally, call callback on every node regardless of success or failure.

Flow Engine Execution Principle

The core of FlowChain.execute is shown below:

public <T> void execute(FlowChain<T> chain, T context) {
    Exception exception = null;
    int index = -1;
    for (FlowNode<T> node : chain.getNodes()) {
        try {
            node.process(context);
            index++;
        } catch (Exception e) {
            if (e instanceof SkipException) {
                CommonLog.warn("当前流程:{} 发出 Skip请求,后续流程不再执行", node.getClass().getSimpleName());
                break;
            }
            exception = e;
            break;
        }
    }
    if (exception != null) {
        for (int i = index; i >= 0; i--) {
            FlowNode<T> node = chain.getNodes().get(i);
            try { node.rollback(context, exception); } catch (Exception e) { CommonLog.error("rollback执行异常,忽略 name:{}", node.getClass().getSimpleName(), e); }
        }
    } else {
        for (int i = index; i >= 0; i--) {
            FlowNode<T> node = chain.getNodes().get(i);
            try { node.success(context); } catch (Exception e) { CommonLog.error("success 执行异常,忽略 name:{}", node.getClass().getSimpleName(), e); }
        }
    }
    for (int i = index; i >= 0; i--) {
        FlowNode<T> node = chain.getNodes().get(i);
        try { node.callback(context, exception); } catch (Exception e) { CommonLog.error("callback执行异常,忽略 name:{}", node.getClass().getSimpleName(), e); }
    }
    if (exception != null) { throw exception; }
}

The full source code resides in the MemberClub repository:

https://gitee.com/-/ide/project/juejinwuyang/memberclub/edit/master/-/memberclub.common/src/main/java/com/memberclub/common/flow/FlowChainService.java