状态机入门实践

状态机是“有限状态自动机”的简称，是一种描述和处理事物状态变化的数学模型。本质上来讲，就是一种比if...else结构更加优雅，并具备可扩展性的状态转移处理机制。有多种实现方案，如：枚举，Spring Statemachine，cola state machine。

枚举状态机

通过在枚举中定义方法来实现状态转移，状态定义及转换图示例如下。
枚举状态转换

public enum FlowState {
    SUBMIT_APPLY {
        FlowState transition(String condition) {
            System.out.println(String.format("员工提交申请，同步流转到部门经理申请，参数:%s", condition));
            return DEPARTMENT_MANAGER_AUDIT;
        }
    },
    DEPARTMENT_MANAGER_AUDIT {
        FlowState transition(String condition) {
            System.out.println(String.format("部门经理审批完成，同步流转到HR审批，参数：%s", condition));
            return HR;
        }
    },
    HR {
        FlowState transition(String condition) {
            System.out.println(String.format("HR审批通过，流转到结束组件，参数：%s", condition));
            return END;
        }
    },
    END {
        FlowState transition(String condition) {
            System.out.println(String.format("流程结束，参数：%s", condition));
            return this;
        }
    };

    // 在枚举中可以定义抽象方法，然后在具体的枚举实例中实现该方法
    abstract FlowState transition(String condition);
}

枚举状态机使用示例：

public class EnumStateMachineSample {
    private FlowState flowState;
    public EnumStateMachineSample() {
        this.flowState = FlowState.SUBMIT_APPLY;
    }

    public void perform(String condition) {
        flowState = flowState.transition(condition);
    }

    public static void main(String[] args) {
        EnumStateMachineSample sample = new EnumStateMachineSample();
        sample.perform("arg1");
        sample.perform("arg2");
        sample.perform("arg3");
        sample.perform("arg4");
    }
}

输出：

员工提交申请，同步流转到部门经理申请，参数:arg1
部门经理审批完成，同步流转到HR审批，参数：arg2
HR审批通过，流转到结束组件，参数：arg3
流程结束，参数：arg4

如上，在运行枚举状态机之后，各个状态的转换按预定方式执行。

Spring Statemachine

依赖Spring框架，具备完整的状态机功能设计。
状态及转换图设计如下：
SpringStateMachine_状态转换

添加依赖：

<!-- spring-statemachine-core -->
<dependency>
    <groupId>org.springframework.statemachine</groupId>
    <artifactId>spring-statemachine-core</artifactId>
    <version>3.0.1</version>
</dependency>
<!-- spring-context -->
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-context</artifactId>
    <version>5.3.8</version>
</dependency>

通过注解方式配置状态机：

@Configuration
@EnableStateMachine
public class StateMachineConfiguration extends StateMachineConfigurerAdapter<String, String> {
    private static final Logger LOGGER = LoggerFactory.getLogger(StateMachineConfiguration.class);

    @Override
    public void configure(StateMachineStateConfigurer<String, String> states) throws Exception {
        // 定义初始节点，结束节点，状态节点
        states.withStates()
                .initial("SS") // 初始节点
                .end("SF") // 结束节点
                .states(new HashSet<String>(Arrays.asList("S1", "S2"))); // 状态节点
    }

    @Override
    public void configure(StateMachineTransitionConfigurer<String, String> transitions) throws Exception {
        // 配置状态节点的事件，流向以及动作
        transitions.withExternal() // 外部流转
                .source("SS").target("S1").event("E1").action(initAction())
                .and()
                .withExternal()
                .source("S1").target("S2").event("E2").action(s1Action())
                .and()
                .withExternal()
                .source("S2").target("SF").event("E3").action(s2Action());
    }

    @Bean
    public Action<String, String> initAction() {
        return new Action<String, String>() {
            public void execute(StateContext<String, String> context) {
                LOGGER.info("Init MyAction -- target: {}", context.getTarget().getId());
            }
        };
    }

    @Bean
    public Action<String, String> s1Action() {
        return new Action<String, String>() {
            public void execute(StateContext<String, String> context) {
                LOGGER.info("S1 MyAction -- target: {}", context.getTarget().getId());
            }
        };
    }

    private Action<String, String> s2Action() {
        return new Action<String, String>() {
            @Override
            public void execute(StateContext<String, String> context) {
                LOGGER.info("S2 MyAction -- target: {}", context.getTarget().getId());
            }
        };
    }

    // 通过Bean注解装配其他bean的属性
    @Bean
    public StateMachineContext stateMachineContext(
            @Qualifier("stateMachine") StateMachine stateMachine,
            @Qualifier("stateMachineListener") StateMachineListener stateMachineListener) {
        // 设置状态机监听器
        stateMachine.addStateListener(stateMachineListener);
        return new StateMachineContext(stateMachine);
    }
}

// StateMachineContext.java
// 这个类的定义不是必须的，存粹是为了方便通过@Bean注解方式配置状态机监听器StateMachineListener
public class StateMachineContext {
    private StateMachine stateMachine;

    public StateMachineContext(StateMachine stateMachine) {
        this.stateMachine = stateMachine;
    }

    public StateMachine getStateMachine() {
        return stateMachine;
    }

    public void setStateMachine(StateMachine stateMachine) {
        this.stateMachine = stateMachine;
    }
}

// 状态机监听器
@Component
public class StateMachineListener extends StateMachineListenerAdapter<String, String> {
    private static final Logger LOGGER = LoggerFactory.getLogger(StateMachineListener.class);
    @Override
    public void stateChanged(State<String, String> from, State<String, String> to) {
        LOGGER.info("Transitioned from {} to {}", from == null ? "none" : from.getId(), to.getId());
    }
}

Spring StateMachine使用示例：

public static void main(String[] args) {
        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
        context.scan("org.chench.extra.java.statemachine.spring"); // 设置状态机相关配置及组件所在的包名
        context.refresh();

        // 从Spring容器中获取状态机实例
        StateMachine<String, String> stateMachine = context.getBean(StateMachine.class);

        // 开启状态机
        stateMachine.startReactively().block();

        // 事件操作，触发状态机内部的状态转换
        Message<String> messageE1 = MessageBuilder.withPayload("E1").build();
        stateMachine.sendEvent(Mono.just(messageE1)).blockLast();

        Message<String> messageE2 = MessageBuilder.withPayload("E2").build();
        stateMachine.sendEvent(Mono.just(messageE2)).blockLast();

        Message<String> messageE3 = MessageBuilder.withPayload("E3").build();
        stateMachine.sendEvent(Mono.just(messageE3)).blockLast();

        // 停止状态机
        stateMachine.stopReactively().block();
    }
}

输出信息如下：

Transitioned from none to SS -- 状态机进入初始状态
Init MyAction -- target: S1  -- 状态机从SS状态转换到S1状态执行的动作
Transitioned from SS to S1   -- 状态机从SS状态转换到S1状态
S1 MyAction -- target: S2    -- 状态机从S1状态转换到S2状态执行的动作
Transitioned from S1 to S2   -- 状态机从S1状态转换到S2状态
S2 MyAction -- target: SF    -- 状态机从S2状态转换到SF状态执行的动作
Transitioned from S2 to SF   -- 状态机从S2状态转换到SF状态

Cola状态机

Cola状态机的使用和配置比Spring StateMachine简单直接，以电商场景的订单状态转换为例进行阐述。
设计订单状态及其转化图如下：
Cola_订单状态转换

添加依赖：

<!-- cola-component-statemachine -->
<dependency>
    <groupId>com.alibaba.cola</groupId>
    <artifactId>cola-component-statemachine</artifactId>
    <version>4.3.2</version>
</dependency>

分别定义订单状态，订单事件，订单上下文。

// 订单状态
public enum OrderStatus {
    INIT("初始化", 0),
    PAY_ONLINE("待支付", 1),
    WAITING_FOR_RECEIVED("待接单", 2),
    WAITING_DELIVERY("待发货", 3),
    PART_DELIVERY("部分发货", 4),
    ALL_DELIVERY("全部发货", 5),
    DELIVER_ALL("待收货", 6),
    RECEIVED("已收货", 7),
    DONE("已完成", 8),
    CANCEL("已关闭", 9);

    private String name;
    private int code;
    OrderStatus(String name, int code) {
        this.name = name;
        this.code = code;
    }

    public String getName() {
        return name;
    }

    public int getCode() {
        return code;
    }
}

// 订单事件
public enum OrderEvent {
    CREATE_ORDER(1, "创建订单"),
    REPAY(2, "支付"),
    CANCEL_ORDER(3, "取消订单"),
    TAKE_ORDER(4, "接单"),
    REJECT_ORDER(5, "拒单"),
    DELIVERY_PART(6, "部分发货"),
    DELIVERY_ALL(7, "全部发货"),
    CONFIRM_RECEIPT(8, "确认收货"),
    EXTEND_RECEIPT(9, "延长收货"),
    COMPLETE(10, "交易完成");

    private int code;
    private String name;
    OrderEvent(int code, String name) {
        this.code = code;
        this.name = name;
    }

    public int getCode() {
        return code;
    }

    public String getName() {
        return name;
    }
}

// 订单上下文
public class OrderContext {
    private String orderId;

    public String getOrderId() {
        return orderId;
    }

    public void setOrderId(String orderId) {
        this.orderId = orderId;
    }
}

使用Cola状态机：

public class ColaStateMachineSample {
    // 状态机实例
    static StateMachine<OrderStatus, OrderEvent, OrderContext> stateMachine;

    public static void main(String[] args) {
        // 状态机构建器
        StateMachineBuilder<OrderStatus, OrderEvent, OrderContext> builder = StateMachineBuilderFactory.create();

        // 设置订单状态转换路径
        // 初始化 -> 待支付
        builder.externalTransition()
                .from(OrderStatus.INIT)
                .to(OrderStatus.PAY_ONLINE)
                .on(OrderEvent.CREATE_ORDER)
                .perform(createOrderAction());

        // 待支付 -> 待接单
        builder.externalTransition()
                .from(OrderStatus.PAY_ONLINE)
                .to(OrderStatus.WAITING_FOR_RECEIVED)
                .on(OrderEvent.REPAY)
                .perform(waitingOrderAction());

        // 待接单 -> 待发货
        builder.externalTransition()
                .from(OrderStatus.WAITING_FOR_RECEIVED)
                .to(OrderStatus.WAITING_DELIVERY)
                .on(OrderEvent.TAKE_ORDER)
                .perform(takeOrderAction());

        // 待发货 -> 部分发货
        builder.externalTransition()
                 .from(OrderStatus.WAITING_DELIVERY)
                 .to(OrderStatus.PART_DELIVERY)
                 .on(OrderEvent.DELIVERY_PART)
                 .perform(deliverPartOrderAction());

        // 部分发货 -> 部分发货 ：内部转换
        builder.internalTransition()
                .within(OrderStatus.PART_DELIVERY)
                .on(OrderEvent.DELIVERY_PART)
                .when(checkOrder())
                .perform(deliverPartOrderAction());

        // 部分发货 -> 全部发货
        builder.externalTransition()
                .from(OrderStatus.PART_DELIVERY)
                .to(OrderStatus.ALL_DELIVERY)
                .on(OrderEvent.DELIVERY_ALL)
                .perform(deliverAllOrderAction());

        // 待发货 -> 全部发货
        builder.externalTransition()
                .from(OrderStatus.WAITING_DELIVERY)
                .to(OrderStatus.ALL_DELIVERY)
                .on(OrderEvent.DELIVERY_ALL)
                .perform(deliverAllOrderAction());

        // 全部发货 -> 待收货
        builder.externalTransition()
                .from(OrderStatus.ALL_DELIVERY)
                .to(OrderStatus.DELIVER_ALL)
                .on(OrderEvent.DELIVERY_ALL)
                .perform(receiveConfirmOrderAction());

        // 待收货 -> 已收货
        builder.externalTransition()
                .from(OrderStatus.DELIVER_ALL)
                .to(OrderStatus.RECEIVED)
                .on(OrderEvent.CONFIRM_RECEIPT)
                .perform(receivedOrderAction());

        // 待支付，待接单，待发货，待收货 -> 已关闭
        builder.externalTransitions()
                .fromAmong(OrderStatus.PAY_ONLINE, OrderStatus.WAITING_FOR_RECEIVED, OrderStatus.WAITING_DELIVERY, OrderStatus.DELIVER_ALL)
                .to(OrderStatus.CANCEL)
                .on(OrderEvent.CANCEL_ORDER)
                .perform(cancelOrderAction());

        // 已收货 -> 已完成
        builder.externalTransition()
                .from(OrderStatus.RECEIVED)
                .to(OrderStatus.DONE)
                .on(OrderEvent.COMPLETE)
                .perform(doneOrderAction());

        // 构建状态机实例
        stateMachine = builder.build("ColaStateMachineSample");

        // 触发创建订单事件，状态转换：“初始化” -> “待支付”
        stateMachine.fireEvent(OrderStatus.INIT, OrderEvent.CREATE_ORDER, new OrderContext());
    }

    // 创建订单
    private static Action<OrderStatus, OrderEvent, OrderContext> createOrderAction() {
        return (from, to, event, context) -> {
            System.out.println("创建订单");
            // 1.获取状态机
            StateMachine<OrderStatus, OrderEvent, OrderContext> stateMachine = getStateMachine();
            // 2.组装订单上下文
            OrderContext orderContext = getOrderContext();
            // 3.触发状态机事件
            stateMachine.fireEvent(OrderStatus.PAY_ONLINE, OrderEvent.REPAY, orderContext);
        };
    }

    // 待接单
    private static Action<OrderStatus, OrderEvent, OrderContext> waitingOrderAction() {
        return (from, to, event, context) -> {
            System.out.println("待接单");

            StateMachine<OrderStatus, OrderEvent, OrderContext> stateMachine = getStateMachine();
            stateMachine.fireEvent(OrderStatus.WAITING_FOR_RECEIVED, OrderEvent.TAKE_ORDER, getOrderContext());
        };
    }

    // 待发货
    private static Action<OrderStatus, OrderEvent, OrderContext> takeOrderAction() {
        return (from, to, event, context) -> {
            System.out.println("待发货");
            StateMachine<OrderStatus, OrderEvent, OrderContext> stateMachine = getStateMachine();

            // 检查是否全部发货
            int r = new Random().nextInt(10);
            if (r % 3 == 0) {
                // 全部发货
                stateMachine.fireEvent(OrderStatus.WAITING_DELIVERY, OrderEvent.DELIVERY_ALL, getOrderContext());
            } else {
                // 部分发货
                stateMachine.fireEvent(OrderStatus.WAITING_DELIVERY, OrderEvent.DELIVERY_PART, getOrderContext());
            }
        };
    }

    // 部分发货
    private static Action<OrderStatus, OrderEvent, OrderContext> deliverPartOrderAction() {
        return (from, to, event, context) ->  {
            System.out.println("部分发货");
            StateMachine<OrderStatus, OrderEvent, OrderContext> stateMachine = getStateMachine();

            // 检查是否还是部分发货
            int r = new Random().nextInt(10);
            if (r % 2 == 0) {
                // 还是部分发货
                stateMachine.fireEvent(OrderStatus.PART_DELIVERY, OrderEvent.DELIVERY_PART, getOrderContext());
            } else {
                // 全部发货
                stateMachine.fireEvent(OrderStatus.PART_DELIVERY, OrderEvent.DELIVERY_ALL, getOrderContext());
            }
        };
    }

    // 检查订单状态
    private static Condition<OrderContext> checkOrder() {
        return new Condition<OrderContext>() {
            @Override
            public boolean isSatisfied(OrderContext context) {
                return true;
            }
        };
    }

    // 全部发货
    private static Action<OrderStatus, OrderEvent, OrderContext> deliverAllOrderAction() {
        return ((from, to, event, context) -> {
            System.out.println("全部发货");
            StateMachine<OrderStatus, OrderEvent, OrderContext> stateMachine = getStateMachine();
            stateMachine.fireEvent(OrderStatus.ALL_DELIVERY, OrderEvent.DELIVERY_ALL, getOrderContext());
        });
    }

    // 待收货
    private static Action<OrderStatus, OrderEvent, OrderContext> receiveConfirmOrderAction() {
        return ((from, to, event, context) -> {
            System.out.println("待收货");
            StateMachine<OrderStatus, OrderEvent, OrderContext> stateMachine = getStateMachine();
            stateMachine.fireEvent(OrderStatus.DELIVER_ALL, OrderEvent.CONFIRM_RECEIPT, getOrderContext());
        });
    }

    // 已收货
    private static Action<OrderStatus, OrderEvent, OrderContext> receivedOrderAction() {
        return ((from, to, event, context) -> {
            System.out.println("已收货");
            StateMachine<OrderStatus, OrderEvent, OrderContext> stateMachine = getStateMachine();
            stateMachine.fireEvent(OrderStatus.RECEIVED, OrderEvent.COMPLETE, getOrderContext());
        });
    }

    // 已关闭
    private static Action<OrderStatus, OrderEvent, OrderContext> cancelOrderAction() {
        return ((from, to, event, context) -> {
            System.out.println("已关闭");
        });
    }

    // 已完成
    private static Action<OrderStatus, OrderEvent, OrderContext> doneOrderAction() {
        return ((from, to, event, context) -> {
            System.out.println("已完成");
        });
    }

    private static StateMachine<OrderStatus, OrderEvent, OrderContext> getStateMachine() {
        return stateMachine;
    }

    private static OrderContext getOrderContext() {
        return new OrderContext();
    }
}

输出：

创建订单
待接单
待发货
部分发货
全部发货
待收货
已收货
已完成

分布式事务框架Seata的SAGA模式就是使用状态机机制实现的，但是其状态转换并非硬编码配置，而是通过状态机设计器进行编排最终导出为json格式文件，每一个分布式事务业务流程就对应一个编排文件。

【参考】
什么是状态机？一篇文章就够了
 状态机的介绍和使用
 状态机的技术选型看这篇就够了,最后一个直叫好！！！
保姆式教程！如何使用Cola-statemachine构建高可靠性的状态机？
Cola-StateMachine状态机的实战使用

posted @ 2024-03-29 21:29 nuccch 阅读(182) 评论(0) 编辑收藏举报

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编程随笔

感兴趣的技术：开发框架，中间件，分布式架构，DevOps

特别说明：本博客属于个人的开发随笔整理，其中的文字可能会随着理解的深入或者变化进行修改，有幸被转载时请标注原始链接^-^

状态机入门实践

枚举状态机

Spring Statemachine

Cola状态机

公告

编程随笔

感兴趣的技术：开发框架，中间件，分布式架构，DevOps 特别说明：本博客属于个人的开发随笔整理，其中的文字可能会随着理解的深入或者变化进行修改，有幸被转载时请标注原始链接^-^

状态机入门实践

枚举状态机

Spring Statemachine

Cola状态机

公告

感兴趣的技术：开发框架，中间件，分布式架构，DevOps

特别说明：本博客属于个人的开发随笔整理，其中的文字可能会随着理解的深入或者变化进行修改，有幸被转载时请标注原始链接^-^