无法从动作触发事件 [英] Unable to Trigger an Event from Action

问题描述

我正在设置Spring状态机事务，我想在Event1完成时启动Event2

I am setting up spring state-machine transactions, i want to launch Event2 on completion of Event1

这些是我所拥有的状态

状态->初始"，第二"，第三"

States -> "INITIAL", "SECOND", "THIRD"

我已将交易配置为通过FIRST_EVENT的操作发送SECOND_EVENT，如下所示

I have configured the transactions to send SECOND_EVENT from action of FIRST_EVENT as shown below

transitions.withExternal()
    .source("INITIAL")
    .target("SECOND")
    .event("FIRST_EVENT")
    .action(new Action<String, String>() {
        @Override
        public void execute(StateContext<String, String> context) {
            System.out.println("FIRST_ACTION_EXECUTED");
            context.getStateMachine().sendEvent("SECOND_EVENT");
        }
    })
    .and()
    .withExternal()
    .source("SECOND")
    .target("THIRD")
    .event("SECOND_EVENT")
    .action(new Action<String, String>() {
        @Override
        public void execute(StateContext<String, String> context) {
            System.out.println("TEST SUCCESS");
        }
    });

在这里，我得到了EvenNotAccepted异常，并且我知道原因是statemachine.getState()是INITIAL，它无法将状态从INITIAL直接更改为THIRD.

Here i get evenNotAccepted exception, and i know the reason is that the statemachine.getState() is INITIAL, and it cant change the state from INITIAL to THIRD directly.

所以我的问题是，无论如何，我是否可以将状态机配置为在第一个事件完成时自动触发第二个事件

So my question is, Is there anyway that i can configure my statemachine to automatically trigger second event on completion of first event

推荐答案

这是因为您使用的操作类型. Spring SM中有两种主要类型的动作- transition 动作和 state 动作-它们在不同的时间解析.您可以在此处看到解决这些问题的顺序.

It's because of the type of actions you're using. There are two main types of actions in the Spring SM - transition actions and state actions - and they resolve on different times. You can see a sequence of resolving of those actions here.

为了触发事件进入下一个状态，您应该使用状态操作.

In order to fire events to go to your next state, you should use state actions.

您可以像这样配置状态操作:

You can configure state actions like so:

   builder.configureStates()
            .withStates()
            .initial(SI)
            .state(F1, context -> context.getStateMachine().sendEvent(E2))
            .state(F2, context -> context.getStateMachine().sendEvent(E3))
            .end(SF);

    builder.configureTransitions()
            .withExternal().source(SI).target(F1).event(E1)
            .and()
            .withExternal().source(F1).target(F2).event(E2)
            .and()
            .withExternal().source(F2).target(SF).event(E3)
                .action(context -> System.out.println("Completing SM!"));

仅手动触发事件E1，将导致以下输出(事件E2和E3通过状态操作自动触发):

Just firing event E1 manually, will result in the following output (events E2 and E3 are auto-fired through state actions):

STATE ENTERED: SI
STAGE TRANSITIONS From: null To: SI
STATE EXITED: SI
STATE ENTERED: F1
STAGE TRANSITIONS From: SI To: F1
21:45:39.153 [pool-2-thread-1] DEBUG org.springframework.statemachine.support.AbstractStateMachine - Queue event GenericMessage [payload=E2, headers={id=393a5636-a760-57d6-a98b-d31eb75f048e, timestamp=1560969939152}] SF F2 F1 SI  / F1 / uuid=4e8773c1-e755-40de-b431-e53a4b0ca64d / id=null
STATE EXITED: F1
STATE ENTERED: F2
STAGE TRANSITIONS From: F1 To: F2
21:45:39.161 [pool-2-thread-1] DEBUG org.springframework.statemachine.support.AbstractStateMachine - Queue event GenericMessage [payload=E3, headers={id=f5899e8b-e4a5-e079-3a30-66114a7accac, timestamp=1560969939161}] SF F2 F1 SI  / F2 / uuid=4e8773c1-e755-40de-b431-e53a4b0ca64d / id=null
Completing SM!
STATE EXITED: F2
STATE ENTERED: SF
STAGE TRANSITIONS From: F2 To: SF

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