Spring-statemachine fork一个region后不能进入join状态的问题

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Spring-statemachine版本：当前最新的1.2.3.RELEASE版本

发现fork多个Region时，子状态全部完成后能够进入join状态。但是如果fork一个Region时Region完成后并不能进入join状态。状态机是StateMachineBuilder.builder()构建的。

然后debug源码很久，发现状态机构建的逻辑是这样的：

org.springframework.statemachine.config.AbstractStateMachineFactory

public StateMachine<S, E> getStateMachine(UUID uuid, String machineId) { ... Collection<StateData<S, E>> stateDatas = popSameParents(stateStack); // stateDatas代表一个区域(Region。拥有相同的父状态)的状态集合 int initialCount = getInitialCount(stateDatas); //获得一个region的初始化状态的数目 Collection<Collection<StateData<S, E>>> regionsStateDatas = splitIntoRegions(stateDatas); Collection<TransitionData<S, E>> transitionsData = getTransitionData(iterator.hasNext(), stateDatas, stateMachineModel); if (initialCount > 1) { // 判断初始化状态数大于1才会通过RegionState创建子状态机 for (Collection<StateData<S, E>> regionStateDatas : regionsStateDatas) { machine = buildMachine(machineMap, stateMap, holderMap, regionStateDatas, transitionsData, resolveBeanFactory(stateMachineModel), contextEvents, defaultExtendedState, stateMachineModel.getTransitionsData(), resolveTaskExecutor(stateMachineModel), resolveTaskScheduler(stateMachineModel), machineId, null, stateMachineModel); regionStack.push(new MachineStackItem<S, E>(machine)); } Collection<Region<S, E>> regions = new ArrayList<Region<S, E>>(); while (!regionStack.isEmpty()) { MachineStackItem<S, E> pop = regionStack.pop(); regions.add(pop.machine); } S parent = (S)peek.getParent(); // 创建类型为RegionState的状态 RegionState<S, E> rstate = buildRegionStateInternal(parent, regions, null, stateData != null ? stateData.getEntryActions() : null, stateData != null ? stateData.getExitActions() : null, new DefaultPseudoState<S, E>(PseudoStateKind.INITIAL)); if (stateData != null) { stateMap.put(stateData.getState(), rstate); } else { // TODO: don't like that we create a last machine here Collection<State<S, E>> states = new ArrayList<State<S, E>>(); states.add(rstate); Transition<S, E> initialTransition = new InitialTransition<S, E>(rstate); // 把RegionState转变成ObjectStateMachine子状态机 StateMachine<S, E> m = buildStateMachineInternal(states, new ArrayList<Transition<S, E>>(), rstate, initialTransition, null, defaultExtendedState, null, contextEvents, resolveBeanFactory(stateMachineModel), resolveTaskExecutor(stateMachineModel), resolveTaskScheduler(stateMachineModel), beanName, machineId != null ? machineId : stateMachineModel.getConfigurationData().getMachineId(), uuid, stateMachineModel); machine = m; } } else { // 如果没有初始化状态或只有一个初始化状态，就构建一个普通的ObjectStateMachine子状态机 machine = buildMachine(machineMap, stateMap, holderMap, stateDatas, transitionsData, resolveBeanFactory(stateMachineModel), contextEvents, defaultExtendedState, stateMachineModel.getTransitionsData(), resolveTaskExecutor(stateMachineModel), resolveTaskScheduler(stateMachineModel), machineId, uuid, stateMachineModel); if (peek.isInitial() || (!peek.isInitial() && !machineMap.containsKey(peek.getParent()))) { machineMap.put(peek.getParent(), machine); } } ... }

从上面的源码可以看出：当子状态机只有一个初始化状态时，不会通过RegionState去创建子状态机。

在同一个类中有个buildMachine方法如下，增加一段"else if"代码后解决问题：

private StateMachine<S, E> buildMachine(Map<Object, StateMachine<S, E>> machineMap, Map<S, State<S, E>> stateMap, Map<S, StateHolder<S, E>> holderMap, Collection<StateData<S, E>> stateDatas, Collection<TransitionData<S, E>> transitionsData, BeanFactory beanFactory, Boolean contextEvents, DefaultExtendedState defaultExtendedState, TransitionsData<S, E> stateMachineTransitions, TaskExecutor taskExecutor, TaskScheduler taskScheduler, String machineId, UUID uuid, StateMachineModel<S, E> stateMachineModel)... // 如果当前状态是虚拟状态，而且类型是JOIN } else if (stateData.getPseudoStateKind() == PseudoStateKind.JOIN) { S s = stateData.getState(); List<S> list = stateMachineTransitions.getJoins().get(s); List<State<S, E>> joins = new ArrayList<State<S,E>>();// if join source is a regionstate, get // it's end states from regions if (list.size() == 1) ｛ State<S, E> ss1 = stateMap.get(list.get(0)); // 判断状态是RegionState时，才会把子状态机的终结状态加入到joins中 if (ss1 instanceof RegionState) { Collection<Region<S, E>> regions = ((RegionState<S, E>)ss1).getRegions(); for (Region<S, E> r : regions) { Collection<State<S, E>> ss2 = r.getStates(); for (State<S, E> ss3 : ss2) { if (ss3.getPseudoState() != null && ss3.getPseudoState().getKind() == PseudoStateKind.END) { joins.add(ss3); continue; } } } // 下面这个else if是我加的代码 // 判断如果当前状态是子状态机状态类型 // 也把子状态的终结状态加入到joins中 } else if (ss1 instanceof StateMachineState) { Collection<State<S, E>> subStates = ((StateMachineState) ss1).getSubmachine().getStates(); for (State<S, E> subState : subStates) { if (subState.getPseudoState() != null && subState.getPseudoState().getKind() == PseudoStateKind.END) { joins.add(subState); } } } } else { for (S fs : list) { joins.add(stateMap.get(fs)); } }List<JoinStateData<S, E>> joinTargets = new ArrayList<JoinStateData<S, E>>(); Collection<TransitionData<S, E>> transitions = stateMachineTransitions.getTransitions(); for (TransitionData<S, E> tt : transitions) { if (tt.getSource() == s) { StateHolder<S, E> holder = new StateHolder<S, E>(stateMap.get(tt.getTarget())); if (holder.getState() == null) { holderMap.put(tt.getTarget(), holder); } joinTargets.add(new JoinStateData<S, E>(holder, tt.getGuard())); } } JoinPseudoState<S, E> pseudoState = new JoinPseudoState<S, E>(joins, joinTargets);state = buildStateInternal(stateData.getState(), stateData.getDeferred(), stateData.getEntryActions(), stateData.getExitActions(), stateData.getStateActions(), pseudoState, stateMachineModel); states.add(state); stateMap.put(stateData.getState(), state); } ... }