状态机方案解决订单状态扭转

状况机机制是一种常用的解决状况改变问题的办法，经过界说状况以及状况之间的搬运规矩来操控状况的流通。关于订单体系，咱们能够运用状况机机制来管理订单状况的改变。

详细来说，咱们能够运用状况机结构来完结订单状况的操控，比方运用 Spring State Machine 结构。以下是运用 Spring State Machine 结构来操控订单状况的示例：

界说订单状况

咱们能够界说订单的各种状况，如下所示：

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public enum OrderState {
    CREATED, // 订单已创立
    PAID, // 订单已付出
    SHIPPED, // 订单已发货
    DELIVERED, // 订单已送达
    CANCELED, // 订单已撤销
    CLOSED // 订单已封闭
}

界说状况机装备

咱们需求界说状况机的装备，包括各个状况和状况之间的搬运规矩，如下所示：

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@Configuration
@EnableStateMachine
public class OrderStateMachineConfig extends StateMachineConfigurerAdapter<OrderState, OrderEvent> {
    @Override
    public void configure(StateMachineTransitionConfigurer<OrderState, OrderEvent> transitions) throws Exception {
        transitions
            .withExternal()
                .source(OrderState.CREATED).target(OrderState.PAID).event(OrderEvent.PAY)
                .and()
            .withExternal()
                .source(OrderState.PAID).target(OrderState.SHIPPED).event(OrderEvent.SHIP)
                .and()
            .withExternal()
                .source(OrderState.SHIPPED).target(OrderState.DELIVERED).event(OrderEvent.DELIVER)
                .and()
            .withExternal()
                .source(OrderState.CREATED).target(OrderState.CANCELED).event(OrderEvent.CANCEL)
                .and()
            .withExternal()
                .source(OrderState.PAID).target(OrderState.CANCELED).event(OrderEvent.CANCEL)
                .and()
            .withExternal()
                .source(OrderState.SHIPPED).target(OrderState.CANCELED).event(OrderEvent.CANCEL);
    }
}

界说事情

咱们需求界说各种事情，如付出、发货、撤销等事情，如下所示：

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public enum OrderEvent {
    PAY, // 付出
    SHIP, // 发货
    DELIVER, // 送达
    CANCEL // 撤销
}

创立状况机

咱们能够运用状况机工厂来创立状况机，如下所示：

javaCopy code
@Configuration
public class OrderStateMachineFactory {
    @Autowired
    private StateMachineFactory<OrderState, OrderEvent> stateMachineFactory;
    public StateMachine<OrderState, OrderEvent> createStateMachine() {
        StateMachine<OrderState, OrderEvent> stateMachine = stateMachineFactory.getStateMachine();
        stateMachine.start();
        return stateMachine;
    }
}

处理状况机事情

当订单发生某种事情时，咱们能够运用状况机来处理事情，如下所示：

承认事情：首要，您需求承认或许发生的事情。关于订单状况机，或许的事情或许包括创立订单、付款、撤销订单等。
界说状况：然后，您需求界说订单状况。关于订单体系，或许的状况包括待付款、待发货、待收货、已完结、已撤销等。
规划状况转化：接下来，您需求规划状况转化，以便在事情发生时主动更改订单状况。例如，当用户完结付出时，订单状况将从待付款转化为待发货。
完结状况机：最终，您需求运用代码完结状况机。在Java中，您能够运用开源库如Spring Statemachine、Squirrel-foundation等来完结状况机。您需求界说状况机的状况、事情和状况转化，以便主动处理订单状况的变化。

以下是一个简略的状况机示例，展示了订单状况的界说和转化：

scssCopy code
public enum OrderState {
    CREATED,
    PAID,
    CANCELLED,
    SHIPPED,
    COMPLETED
}
public enum OrderEvent {
    PAY,
    CANCEL,
    SHIP,
    COMPLETE
}
public void configure(StateMachineTransitionConfigurer<OrderState, OrderEvent> transitions) throws Exception {
    transitions
        .withExternal().source(OrderState.CREATED).target(OrderState.PAID).event(OrderEvent.PAY)
        .and()
        .withExternal().source(OrderState.PAID).target(OrderState.SHIPPED).event(OrderEvent.SHIP)
        .and()
        .withExternal().source(OrderState.SHIPPED).target(OrderState.COMPLETED).event(OrderEvent.COMPLETE)
        .and()
        .withExternal().source(OrderState.CREATED).target(OrderState.CANCELLED).event(OrderEvent.CANCEL)
        .and()
        .withExternal().source(OrderState.PAID).target(OrderState.CANCELLED).event(OrderEvent.CANCEL)
        .and()
        .withExternal().source(OrderState.SHIPPED).target(OrderState.CANCELLED).event(OrderEvent.CANCEL);
}
public void onPay() {
    // 订单付出成功
}
public void onShip() {
    // 订单发货
}
public void onComplete() {
    // 订单完结
}
public void onCancel() {
    // 订单撤销
}

在此示例中，咱们界说了订单状况（OrderState）和事情（OrderEvent）。然后，咱们运用withExternal()办法界说状况转化，并指定源状况、方针状况和触发转化的事情。最终，咱们界说了处理不同事情的办法。

当某个事情发生时，状况时机主动触发状况转化，并调用相应的事情处理办法，从而更改订单状况。

如果需求完结一个高可用的状况机，能够考虑运用分布式状况机，例如运用 ZooKeeper 或 etcd 完结分布式协同。在这种状况下，每个节点都能够处理事情并更新状况，节点之间能够经过协同算法坚持一致性。这种办法能够确保状况机的可靠性和高可用性，但需求考虑一些杂乱性，例如如何处理网络分区和节点毛病等问题。

好的，下面是一个运用 ZooKeeper 完结分布式状况机的示例：

首要，需求引入 ZooKeeper 的 Java 客户端库：

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  <dependency>
    <groupId>org.apache.zookeeper</groupId>
    <artifactId>zookeeper</artifactId>
    <version>3.6.3</version>
</dependency>

在代码中创立 ZooKeeper 客户端：

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public class ZooKeeperClient {
    private static final String CONNECTION_STRING = "localhost:2181";
    private static final int SESSION_TIMEOUT_MS = 5000;
    private static final int CONNECT_TIMEOUT_MS = 5000;
    private static final String BASE_PATH = "/order-state";
    private final ZooKeeper zooKeeper;
    public ZooKeeperClient() throws IOException {
        this.zooKeeper = new ZooKeeper(CONNECTION_STRING, SESSION_TIMEOUT_MS, new Watcher() {
            @Override
            public void process(WatchedEvent event) {
                // handle event
            }
        });
    }
    public void close() throws InterruptedException {
        zooKeeper.close();
    }
    public String createNode(String path, byte[] data) throws KeeperException, InterruptedException {
        return zooKeeper.create(BASE_PATH + path, data, ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT_SEQUENTIAL);
    }
    public byte[] getData(String path) throws KeeperException, InterruptedException {
        return zooKeeper.getData(BASE_PATH + path, false, null);
    }
    public void setData(String path, byte[] data) throws KeeperException, InterruptedException {
        zooKeeper.setData(BASE_PATH + path, data, -1);
    }
    public void deleteNode(String path) throws KeeperException, InterruptedException {
        zooKeeper.delete(BASE_PATH + path, -1);
    }
}

这个类封装了 ZooKeeper 客户端的一些根本操作，例如创立节点、获取数据、更新数据和删去节点等。

创立一个订单状况机：

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public class OrderStateMachine {
    private final ZooKeeperClient client;
    private final String orderId;
    private final Map<OrderState, Set<OrderState>> transitions;
    private OrderState currentState;
    public OrderStateMachine(ZooKeeperClient client, String orderId) {
        this.client = client;
        this.orderId = orderId;
        this.transitions = new HashMap<>();
        this.currentState = OrderState.CREATED;
        // Define transitions
        transitions.put(OrderState.CREATED, EnumSet.of(OrderState.PAYED, OrderState.CANCELED));
        transitions.put(OrderState.PAYED, EnumSet.of(OrderState.SHIPPED, OrderState.CANCELED));
        transitions.put(OrderState.SHIPPED, EnumSet.of(OrderState.DELIVERED, OrderState.CANCELED));
        transitions.put(OrderState.DELIVERED, EnumSet.noneOf(OrderState.class));
        transitions.put(OrderState.CANCELED, EnumSet.noneOf(OrderState.class));
        // Initialize state
        try {
            byte[] data = client.getData(orderId);
            if (data != null) {
                this.currentState = OrderState.valueOf(new String(data));
            }
        } catch (Exception e) {
            // Handle exception
        }
    }
    public synchronized void handleEvent(OrderEvent event) {
        Set<OrderState> validTransitions = transitions.get(currentState);
        if (validTransitions != null && validTransitions.contains(event.getTargetState())) {
            try {
                // Update state in ZooKeeper
                client.setData(orderId, event.getTargetState().name().getBytes());
                // Update local state
                currentState = event.getTargetState();
            } catch (Exception e) {
                // Handle exception
            }

创立订单状况机的过程能够分为以下几个步骤：

承认状况和事情

首要，需求承认订单状况和或许触发的事情。关于一个简略的订单体系，或许的状况和事情如下：

订单已创立（CREATED）付出（PAY）撤销（CANCEL）
订单已付出（PAID）发货（SHIP）撤销（CANCEL）
订单已发货（SHIPPED）承认收货（RECEIVE）撤销（CANCEL）
订单已完结（RECEIVED）

规划状况搬运图

然后，依据状况和事情，规划状况搬运图。状况搬运图用于表示状况之间的转化关系，以及何时触发转化。

下图是一个简略的订单状况搬运图：

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+-------+
              |       |
              |  待付出  +---------+
              |       |            |
              +-------+            |
                 |                 |
                 |                 |
                 v                 |
              +-------+            |
              |       |            |
              |  已付出  +------+ |
              |       |        | |
              +-------+        | |
                 |             | |
                 |             | |
                 v             | |
              +-------+        | |
              |       |        | |
              |  已发货  +------+ |
              |       |           |
              +-------+           |
                 |                 |
                 |                 |
                 v                 |
              +-------+            |
              |       |            |
              | 已收货  | <---------+
              |       |
              +-------+

在状况搬运图中，每个圆圈代表一个状况，每个箭头代表一条搬运。箭头上标注的是触发搬运的事情。

完结状况机

最终，运用代码完结状况机。详细完结办法或许因编程语言和状况机库而异，这里以 Java 和 Spring 状况机为例：

scssCopy code
@Configuration
@EnableStateMachine
public class OrderStateMachineConfig extends EnumStateMachineConfigurerAdapter<OrderStatus, OrderEvent> {
    @Override
    public void configure(StateMachineStateConfigurer<OrderStatus, OrderEvent> states) throws Exception {
        states.withStates()
                .initial(OrderStatus.CREATED)
                .states(EnumSet.allOf(OrderStatus.class));
    }
    @Override
    public void configure(StateMachineTransitionConfigurer<OrderStatus, OrderEvent> transitions) throws Exception {
        transitions
                .withExternal()
                    .source(OrderStatus.CREATED).target(OrderStatus.PAID).event(OrderEvent.PAY)
                    .and()
                .withExternal()
                    .source(OrderStatus.PAID).target(OrderStatus.SHIPPED).event(OrderEvent.SHIP)
                    .and()
                .withExternal()
                    .source(OrderStatus.SHIPPED).target(OrderStatus.RECEIVED).event(OrderEvent.RECEIVE)
                    .and()
                .withExternal()
                    .source(OrderStatus.CREATED).target(OrderStatus.CANCELED).event(OrderEvent.CANCEL)
                    .and()
                .withExternal()
                    .source(OrderStatus.PAID).target(OrderStatus.CANCELED).event(OrderEvent.CANCEL)
                    .and()
                .withExternal()
                    .source(OrderStatus.SHIPPED).target(OrderStatus.CANCELED).event(OrderEvent.CANCEL);
    }
}

以下是一个基于 Java 和 Spring 状况机的订单状况机的代码示例：

javaCopy code@Configuration
@EnableStateMachine
public class OrderStateMachineConfig extends EnumStateMachineConfigurerAdapter<OrderStatus, OrderEvent> {
    @Autowired
    private OrderStateChangeInterceptor orderStateChangeInterceptor;
    @Override
    public void configure(StateMachineConfigurationConfigurer<OrderStatus, OrderEvent> config) throws Exception {
        config
                .withConfiguration()
                .autoStartup(true)
                .listener(orderStateChangeInterceptor);
    }
    @Override
    public void configure(StateMachineStateConfigurer<OrderStatus, OrderEvent> states) throws Exception {
        states
                .withStates()
                .initial(OrderStatus.CREATED)
                .state(OrderStatus.PAID)
                .state(OrderStatus.CONFIRMED)
                .state(OrderStatus.SHIPPED)
                .state(OrderStatus.DELIVERED)
                .end(OrderStatus.COMPLETED)
                .end(OrderStatus.CANCELED);
    }
    @Override
    public void configure(StateMachineTransitionConfigurer<OrderStatus, OrderEvent> transitions) throws Exception {
        transitions
                .withExternal()
                .source(OrderStatus.CREATED)
                .target(OrderStatus.PAID)
                .event(OrderEvent.PAY)
                .and()
                .withExternal()
                .source(OrderStatus.PAID)
                .target(OrderStatus.CONFIRMED)
                .event(OrderEvent.CONFIRM)
                .and()
                .withExternal()
                .source(OrderStatus.CONFIRMED)
                .target(OrderStatus.SHIPPED)
                .event(OrderEvent.SHIP)
                .and()
                .withExternal()
                .source(OrderStatus.SHIPPED)
                .target(OrderStatus.DELIVERED)
                .event(OrderEvent.DELIVER)
                .and()
                .withExternal()
                .source(OrderStatus.DELIVERED)
                .target(OrderStatus.COMPLETED)
                .event(OrderEvent.COMPLETE)
                .and()
                .withExternal()
                .source(OrderStatus.CREATED)
                .target(OrderStatus.CANCELED)
                .event(OrderEvent.CANCEL)
                .and()
                .withExternal()
                .source(OrderStatus.PAID)
                .target(OrderStatus.CANCELED)
                .event(OrderEvent.CANCEL)
                .and()
                .withExternal()
                .source(OrderStatus.CONFIRMED)
                .target(OrderStatus.CANCELED)
                .event(OrderEvent.CANCEL)
                .and()
                .withExternal()
                .source(OrderStatus.SHIPPED)
                .target(OrderStatus.CANCELED)
                .event(OrderEvent.CANCEL)
                .and()
                .withExternal()
                .source(OrderStatus.DELIVERED)
                .target(OrderStatus.CANCELED)
                .event(OrderEvent.CANCEL);
    }
}

在这个示例中，咱们界说了订单状况机的状况和事情。在 configure(
StateMachineConfigurationConfigurer<OrderStatus, OrderEvent> config) 办法中，咱们装备了状况机的发动和事情监听器。在 configure(StateMachineStateConfigurer<OrderStatus, OrderEvent> states) 办法中，咱们界说了订单状况机的状况。在 configure(StateMachineTransitionConfigurer<OrderStatus, OrderEvent> transitions) 办法中，咱们界说了状况机的事情和状况之间的转化。在 source 中指定开始状况，在 target 中指定方针状况，在 event 中指定事情。

最终，咱们还需求创立一个状况机事情拦截器，用于在状况机状况转化时履行自界说逻辑，比方修正订单状况、记载状况转化日志等。下面是

以下是一个简略的状况机事情拦截器的代码示例：

javaCopy codepublic class OrderStateChangeInterceptor extends StateMachineInterceptorAdapter<OrderStatus, OrderStatusChangeEvent> {
    @Override
    public void preStateChange(State<OrderStatus, OrderStatusChangeEvent> state, Message<OrderStatusChangeEvent> message, Transition<OrderStatus, OrderStatusChangeEvent> transition, StateMachine<OrderStatus, OrderStatusChangeEvent> stateMachine) {
        // 依据状况搬运状况更新订单状况
        if (transition.getTarget().getId() == OrderStatus.PAID) {
            // 更新订单为已付出状况
            updateOrderStatus(message.getHeaders().get("orderId"), OrderStatus.PAID);
        } else if (transition.getTarget().getId() == OrderStatus.CANCELED) {
            // 更新订单为已撤销状况
            updateOrderStatus(message.getHeaders().get("orderId"), OrderStatus.CANCELED);
        }
        // 记载状况搬运日志
        recordStateChangeLog(message.getHeaders().get("orderId"), transition.getSource().getId(), transition.getTarget().getId());
    }
    private void updateOrderStatus(String orderId, OrderStatus status) {
        // 履行更新订单状况的事务逻辑
    }
    private void recordStateChangeLog(String orderId, OrderStatus fromStatus, OrderStatus toStatus) {
        // 记载状况搬运日志的事务逻辑
    }
}

在拦截器的 preStateChange 办法中，咱们能够依据状况搬运状况履行自界说的事务逻辑，比方更新订单状况、记载状况搬运日志等。在这个示例中，咱们依据状况搬运方针状况更新订单状况，并记载状况搬运日志。在详细事务完结中，咱们能够依据需求扩展拦截器的逻辑。

完整的状况机完结和拦截器代码示例如下：

javaCopy code
@Configuration
@EnableStateMachine
public class OrderStateMachineConfig extends EnumStateMachineConfigurerAdapter<OrderState, OrderEvent> {
    @Autowired
    private OrderService orderService;
    @Override
    public void configure(StateMachineConfigurationConfigurer<OrderState, OrderEvent> config) throws Exception {
        config
                .withConfiguration()
                .autoStartup(true)
                .listener(new StateMachineListenerAdapter<OrderState, OrderEvent>() {
                    @Override
                    public void stateChanged(State<OrderState, OrderEvent> from, State<OrderState, OrderEvent> to) {
                        log.info("Order status changed from {} to {}", from.getId(), to.getId());
                    }
                });
    }
    @Override
    public void configure(StateMachineStateConfigurer<OrderState, OrderEvent> states) throws Exception {
        states
                .withStates()
                .initial(OrderState.SUBMITTED)
                .state(OrderState.PAID)
                .state(OrderState.FULFILLED)
                .state(OrderState.CANCELLED)
                .end(OrderState.COMPLETED);
    }
    @Override
    public void configure(StateMachineTransitionConfigurer<OrderState, OrderEvent> transitions) throws Exception {
        transitions
                .withExternal()
                .source(OrderState.SUBMITTED).target(OrderState.PAID).event(OrderEvent.PAY)
                .and()
                .withExternal()
                .source(OrderState.PAID).target(OrderState.FULFILLED).event(OrderEvent.FULFILL)
                .and()
                .withExternal()
                .source(OrderState.SUBMITTED).target(OrderState.CANCELLED).event(OrderEvent.CANCEL)
                .and()
                .withExternal()
                .source(OrderState.PAID).target(OrderState.CANCELLED).event(OrderEvent.CANCEL);
    }
    @Bean
    public StateMachineInterceptor<OrderState, OrderEvent> stateMachineInterceptor() {
        return new StateMachineInterceptorAdapter<OrderState, OrderEvent>() {
            @Override
            public void preStateChange(State<OrderState, OrderEvent> state, Message<OrderEvent> message, Transition<OrderState, OrderEvent> transition, StateMachine<OrderState, OrderEvent> stateMachine) {
                OrderState targetState = transition.getTarget().getId();
                Order order = stateMachine.getExtendedState().get("order", Order.class);
                if (order != null) {
                    order.setState(targetState);
                    orderService.updateOrder(order);
                    log.info("Order status updated to {}", targetState);
                    log.info("Record order state change log, from {} to {}", state.getId(), targetState);
                }
            }
        };
    }
    @Override
    public void configure(StateMachineInterceptorConfigurer<OrderState, OrderEvent> interceptors) throws Exception {
        interceptors
                .withInterceptor(stateMachineInterceptor())
                .order(-1);
    }
}

在上述示例中，咱们创立了一个 Spring 状况机，并界说了四个订单状况：SUBMITTED、PAID、FULFILLED 和 CANCELLED。咱们还界说了三个状况搬运事情：PAY、FULFILL 和 CANCEL。

咱们在拦截器的 preStateChange 办法中，依据状况搬运方针状况更新订单状况，并记载状况搬运日志。在详细事务完结中，咱们能够依据需求扩展拦截器的逻辑。

好的，咱们能够在拦截器的 preStateChange 办法中，依据状况搬运方针状况更新订单状况，并记载状况搬运日志。在详细事务完结中，咱们能够依据需求扩展拦截器的逻辑。以下是示例代码：

javaCopy code@Component
public class OrderStateChangeInterceptor extends StateMachineInterceptorAdapter<OrderStates, OrderEvents> {
    @Autowired
    private OrderService orderService;
    @Override
    public void preStateChange(State<OrderStates, OrderEvents> state, Message<OrderEvents> message, Transition<OrderStates, OrderEvents> transition, StateMachine<OrderStates, OrderEvents> stateMachine) {
        // 获取订单号
        String orderId = message.getHeaders().get(OrderConstant.ORDER_ID_HEADER, String.class);
        // 获取方针状况
        OrderStates targetState = transition.getTarget().getId();
        // 更新订单状况
        orderService.updateOrderStatus(orderId, targetState);
        // 记载状况搬运日志
        orderService.saveOrderLog(orderId, targetState);
    }
}

在上述示例中，咱们经过 OrderService 来更新订单状况和保存状况搬运日志。详细的完结能够依据事务需求自行完结。

然后，咱们需求将拦截器装备到状况机中，如下所示：

javaCopy code@Configuration
@EnableStateMachine
public class StateMachineConfig extends StateMachineConfigurerAdapter<OrderStates, OrderEvents> {
    // ... 状况机装备代码 ...
    @Autowired
    private OrderStateChangeInterceptor orderStateChangeInterceptor;
    @Override
    public void configure(StateMachineInterceptorConfigurer<OrderStates, OrderEvents> configurer) throws Exception {
        configurer
            .withInterceptor(orderStateChangeInterceptor);
    }
}

在上述示例中，咱们将拦截器经过 withInterceptor 办法添加到状况机中。这样，在状况搬运时，就会触发拦截器中的 preStateChange 办法，从而履行自界说的事务逻辑。

是的，当状况机履行状况搬运时，会调用拦截器中的 preStateChange 办法，从而履行自界说的事务逻辑。拦截器能够在状况搬运前后履行逻辑，比方记载日志、更新状况等，从而完结状况机的扩展。在详细的事务场景中，咱们能够依据需求扩展拦截器的逻辑，以满意详细的需求。

需求注意的是，拦截器中的事务逻辑应该尽量简略，不要耗时过长，以防止影响状况搬运的性能。同时，拦截器中的逻辑也应该考虑反常状况的处理，比方事务回滚、反常记载等。

总的来说，状况机是一种十分强壮的东西，能够用于完结杂乱的事务逻辑。在实际使用中，咱们应该依据详细的事务场景挑选适宜的状况机库，并结合拦截器、事情等机制，以完结状况机的灵活性和可扩展性。

状态机方案解决订单状态扭转

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