介绍

squirrel-foundation：轻量级java有限状态机

状态机的要素

状态机可归纳为4个要素，即现态、条件、动作、次态。“现态”和“条件”是因，“动作”和“次态”是果。

现态:是指当前所处的状态。

条件:又称为事件。当一个条件被满足，将会触发一个动作，或者执行一次状态的迁移。

动作:条件满足后执行的动作。动作执行完毕后，可以迁移到新的状态，也可以仍旧保持原状态。动作不是必需的，当条件满足后，也可以不执行任何动作，直接迁移到新状态。

次态:条件满足后要迁往的新状态。“次态”是相对于“现态”而言的，“次态”一旦被激活，就转变成新的“现态”了。

入门级Demo

导入依赖


       
    
     org.squirrelframework
        
    
     squirrel-foundation
        
    
     0.3.8

StateMachine接口需要以下4种泛型参数。

T代表实现的状态机类型。

S代表实现的状态类型。

E代表实现的事件类型。

C代表实现的外部上下文类型。

定义S：即状态类型

public enum  MyState {    A,    B,    C,    D;}

定义E：即事件类型

public enum  MyEvent {    ToA,ToB,ToC,ToD;}

定义C：即上下文类型，只有一个num字段

public class MyContext {    public int num = 0;    public int getNum() {        return num;    }    public void setNum(int num) {        this.num = num;    }}

定义T：状态机类型

/** * 定义我的状态机：需继承AbstractStateMachine */public class MyStateMachine extends AbstractStateMachine
   
     {    public void fun1(MyState from, MyState to, MyEvent event, MyContext context) {        System.out.println("fun1() 方法执行了。。。。。。。。。。。。。 from：" + from + ", to:" + to +", event:" +event +", context:" + context.num );    }}

编写main函数

public static void main(String[] args) {        StateMachineBuilder
   
     builder =                StateMachineBuilderFactory.create(MyStateMachine.class, MyState.class, MyEvent.class, MyContext.class);        /**         * 条件为：content.getNum 为20的时候转换，并执行fun1()方法         */        builder.externalTransition().from(MyState.A).to(MyState.B).on(MyEvent.ToB)                .whenMvel("myCondition:::(context!=null && context.getNum() == 20)").callMethod("fun1");        MyStateMachine machine = builder.newStateMachine(MyState.A);        machine.start();        System.out.println("currentState is " + machine.getCurrentState());        MyContext context = new MyContext();        context.setNum(20);        machine.fire(MyEvent.ToB, context);        System.out.println("currentState is " + machine.getCurrentState());            }

结果打印

currentState is Afun1() 方法执行了。。。。。。。。。。。。。 from：A, to:B, event:toB, context:20currentState is B

添加监听和注解开发

修改T，增加监听

/** * 定义我的状态机：需继承AbstractStateMachine */public class MyStateMachine extends AbstractStateMachine
   
     {    public void fun1(MyState from, MyState to, MyEvent event, MyContext context) {        System.out.println("fun1() 方法执行了。。。。。。。。。。。。。 from：" + from + ", to:" + to + ", event:" + event + ", context:" + context.num);    }     /**     * 约定大于配置     * like：     * transitFrom[fromStateName]To[toStateName]On[eventName]When[conditionName]     * transitFrom[fromStateName]To[toStateName]On[eventName]     * transitFromAnyTo[toStateName]On[eventName]     * transitFrom[fromStateName]ToAnyOn[eventName]     * transitFrom[fromStateName]To[toStateName]     * on[eventName]     */    protected void transitFromAToBOnToB(MyState from, MyState to, MyEvent event, MyContext context){        System.out.println("从A--->B执行....约定大于配置");    }    /**     * exitA执行     */    protected void exitA(MyState from, MyState to, MyEvent event, MyContext context){        System.out.println("exitA()方法执行了。。。。。。。。");    }    public class DeclarativeListener {        @OnTransitionBegin        public void transitionBegin(MyEvent event) {            // method annotated with TransitionBegin will be invoked when transition begin...            System.out.println("转换开始执行.." + event);        }        /**         * 条件：context.num == 20 || event.name().equals("toC")         */        @OnTransitionBegin(when = "context.num == 20 || event.name().equals(\"toC\")")        public void begins(MyState from, MyState to, MyEvent event, MyContext context) {            System.out.println("begins 执行了， from：" + from + ", to:" + to + ", event:" + event + ", context:" + context.num);        }        @OnTransitionEnd        @ListenerOrder(10) // Since 0.3.1 ListenerOrder can be used to insure listener invoked orderly        public void transitionEnd() {            // method annotated with TransitionEnd will be invoked when transition end...            // the method must be public and return nothing            System.out.println("转换结束执行..");        }        @OnTransitionComplete        public void transitionComplete(String from, String to, MyEvent event, Integer context) {            // method annotated with TransitionComplete will be invoked when transition complete...            System.out.println("转换成功执行..");        }        @OnTransitionDecline        public void transitionDeclined(String from, MyEvent event, Integer context) {            // method annotated with TransitionDecline will be invoked when transition declined...            System.out.println("转换拒绝执行..");        }        @OnBeforeActionExecuted        public void onBeforeActionExecuted(Object sourceState, Object targetState,                                           Object event, Object context, int[] mOfN, Action
     action) {            // method annotated with OnAfterActionExecuted will be invoked before action invoked            System.out.println("状态机内方法动作执行之前...111111111111111111111111111111111");        }        @OnAfterActionExecuted        public void onAfterActionExecuted(Object sourceState, Object targetState,                                          Object event, Object context, int[] mOfN, Action
     action) {            // method annotated with OnAfterActionExecuted will be invoked after action invoked            System.out.println("状态机内方法动作执行之后...222222222222222222222222222222222");        }        @OnActionExecException        public void onActionExecException(Action
     action, TransitionException e) {            // method annotated with OnActionExecException will be invoked when action thrown exception            System.out.println("转换异常执行。。");        }    }}

再次编写Main函数

public static void main(String[] args) {        StateMachineBuilder
   
     builder =                StateMachineBuilderFactory.create(MyStateMachine.class, MyState.class, MyEvent.class, MyContext.class);        /**         * 条件为：content.getNum 为20的时候转换，并执行fun1()方法         */        builder.externalTransition().from(MyState.A).to(MyState.B).on(MyEvent.ToB)                .whenMvel("myCondition:::(context!=null && context.getNum() == 20)").callMethod("fun1");        builder.externalTransition().from(MyState.A).to(MyState.C).on(MyEvent.ToC);        MyStateMachine machine = builder.newStateMachine(MyState.A);        machine.addDeclarativeListener(machine.new DeclarativeListener());        machine.start();        System.out.println("currentState is " + machine.getCurrentState());        MyContext context = new MyContext();        context.setNum(20);        machine.fire(MyEvent.ToB, context);        System.out.println("currentState is " + machine.getCurrentState());    }

结果打印

currentState is Abegins 执行了， from：A, to:null, event:ToB, context:20转换开始执行..ToB状态机内方法动作执行之前...111111111111111111111111111111111exitA()方法执行了。。。。。。。。状态机内方法动作执行之后...222222222222222222222222222222222状态机内方法动作执行之前...111111111111111111111111111111111fun1() 方法执行了。。。。。。。。。。。。。 from：A, to:B, event:ToB, context:20状态机内方法动作执行之后...222222222222222222222222222222222状态机内方法动作执行之前...111111111111111111111111111111111从A--->B执行....约定大于配置状态机内方法动作执行之后...222222222222222222222222222222222转换成功执行..转换结束执行..currentState is B

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