cola状态机

一. 设计思路

1.1 状态机领域模型

• State：状态

• Event：事件，状态由事件触发，引起变化

• Transition：流转，表示从一个状态到另一个状态

• External Transition：外部流转，两个不同状态之间的流转

• Internal Transition：内部流转，同一个状态之间的流转

• Condition：条件，表示是否允许到达某个状态

• Action：动作，到达某个状态之后，可以做什么

• StateMachine：状态机

1.2 细节设计

1. 一个起始状态和一个事件唯一确定一个目标状态

2. 一个起始状态经过不同事件可以流转到同一状态或不同状态

二. 使用方法

2.1 外部流转

    @Test
    public void testExternalNormal() {
        StateMachineBuilder<States, Events, Context> builder = StateMachineBuilderFactory.create();
        builder.externalTransition()
            .from(States.STATE1)
            .to(States.STATE2)
            .on(Events.EVENT1)
            .when(checkCondition())
            .perform(doAction());

        StateMachine<States, Events, Context> stateMachine = builder.build(MACHINE_ID);
        States target = stateMachine.fireEvent(States.STATE1, Events.EVENT1, new Context());
        Assert.assertEquals(States.STATE2, target);
    }

2.2 内部流转

    @Test
    public void testInternalNormal() {
        StateMachineBuilder<States, Events, Context> builder = StateMachineBuilderFactory.create();
        builder.internalTransition()
            .within(States.STATE1)
            .on(Events.INTERNAL_EVENT)
            .when(checkCondition())
            .perform(doAction());
        StateMachine<States, Events, Context> stateMachine = builder.build(MACHINE_ID + "2");

        stateMachine.fireEvent(States.STATE1, Events.EVENT1, new Context());
        States target = stateMachine.fireEvent(States.STATE1, Events.INTERNAL_EVENT, new Context());
        Assert.assertEquals(States.STATE1, target);
    }

2.3 条件流转

@Test
    public void testChoice(){
        StateMachineBuilder<StateMachineTest.States, StateMachineTest.Events, Context> builder = StateMachineBuilderFactory.create();
        builder.internalTransition()
            .within(StateMachineTest.States.STATE1)
            .on(StateMachineTest.Events.EVENT1)
            .when(checkCondition1())
            .perform(doAction());
        builder.externalTransition()
            .from(StateMachineTest.States.STATE1)
            .to(StateMachineTest.States.STATE2)
            .on(StateMachineTest.Events.EVENT1)
            .when(checkCondition2())
            .perform(doAction());
        builder.externalTransition()
            .from(StateMachineTest.States.STATE1)
            .to(StateMachineTest.States.STATE3)
            .on(StateMachineTest.Events.EVENT1)
            .when(checkCondition3())
            .perform(doAction());

        StateMachine<StateMachineTest.States, StateMachineTest.Events, Context> stateMachine = builder.build("ChoiceConditionMachine");
        StateMachineTest.States target1 = stateMachine.fireEvent(StateMachineTest.States.STATE1, StateMachineTest.Events.EVENT1, new Context("1"));
        Assert.assertEquals(StateMachineTest.States.STATE1,target1);
        StateMachineTest.States target2 = stateMachine.fireEvent(StateMachineTest.States.STATE1, StateMachineTest.Events.EVENT1, new Context("2"));
        Assert.assertEquals(StateMachineTest.States.STATE2,target2);
        StateMachineTest.States target3 = stateMachine.fireEvent(StateMachineTest.States.STATE1, StateMachineTest.Events.EVENT1, new Context("3"));
        Assert.assertEquals(StateMachineTest.States.STATE3,target3);
    }

2.4 多对一流转

  /**
   * 取消订单: 待支付、待发货、待收货 -> 待支付
   * externalTransitions : 用于多个流转的构建器
   */
  builder.externalTransitions()
    .fromAmong(OrderStatusEnum.PAY_ONLINE,OrderStatusEnum.WAITING_FOR_RECEIVED,OrderStatusEnum.WAITING_DELIVERY)
    .to(OrderStatusEnum.CANCEL)
    .on(OrderEventEnum.CANCEL_ORDER)
    .when(checkOrder())
    .perform(cancelOrderAction);