设计模式-利用状态机实现订单状态流转控制

状态机是状态模式的一种应用，相当于上下文角色的一个升级版。在工作流和游戏中有大量使用。如各种工作流引擎，几乎是状态机的子集和实现，封装状态的变化规则。Spring也给我们提供了一个很好的解决方案。在spring中的组件名称就叫StateMachine。状态机简化状态控制的开发过程，让状态机结构更加层次化。下面，我们用spring的状态机模拟一个订单流转的过程。

一、添加依赖（maven）

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

二、创建订单实体类Order

package com.caozz.demo2.state.statemachine;

public class Order {
    private int id;
    private OrderStatus status;
    public void setStatus(OrderStatus status) {
        this.status = status;
    }

    public OrderStatus getStatus() {
        return status;
    }

    public void setId(int id) {
        this.id = id;
    }

    public int getId() {
        return id;
    }

    @Override
    public String toString() {
        return "订单号：" + id + ", 订单状态：" + status;
    }
}

三、创建订单状态枚举类以及状态转换事件枚举类

package com.caozz.demo2.state.statemachine;

/**
 * 订单状态
 */
public enum OrderStatus {
    // 待支付，待发货，待收货，订单结束
    WAIT_PAYMENT, WAIT_DELIVER, WAIT_RECEIVE, FINISH;
}

package com.caozz.demo2.state.statemachine;

/**
 * 订单状态改变事件
 */
public enum OrderStatusChangeEvent {
    // 支付，发货，确认收货
    PAYED, DELIVERY, RECEIVED;
}

四、添加状态流转配置

package com.caozz.demo2.state.statemachine;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.statemachine.StateMachineContext;
import org.springframework.statemachine.StateMachinePersist;
import org.springframework.statemachine.config.EnableStateMachine;
import org.springframework.statemachine.config.StateMachineConfigurerAdapter;
import org.springframework.statemachine.config.builders.StateMachineStateConfigurer;
import org.springframework.statemachine.config.builders.StateMachineTransitionConfigurer;
import org.springframework.statemachine.persist.DefaultStateMachinePersister;
import org.springframework.statemachine.support.DefaultStateMachineContext;

import java.util.EnumSet;

/**
 * 订单状态机配置
 */
@Configuration
@EnableStateMachine(name = "orderStateMachine")
public class OrderStateMachineConfig extends StateMachineConfigurerAdapter<OrderStatus, OrderStatusChangeEvent> {
 
    /**
     * 配置状态
     * @param states
     * @throws Exception
     */
    public void configure(StateMachineStateConfigurer<OrderStatus, OrderStatusChangeEvent> states) throws Exception {
        states
                .withStates()
                .initial(OrderStatus.WAIT_PAYMENT)
                .states(EnumSet.allOf(OrderStatus.class));
    }
 
    /**
     * 配置状态转换事件关系
     * @param transitions
     * @throws Exception
     */
    public void configure(StateMachineTransitionConfigurer<OrderStatus, OrderStatusChangeEvent> transitions) throws Exception {
        transitions
                .withExternal().source(OrderStatus.WAIT_PAYMENT).target(OrderStatus.WAIT_DELIVER).event(OrderStatusChangeEvent.PAYED)
                .and()
                .withExternal().source(OrderStatus.WAIT_DELIVER).target(OrderStatus.WAIT_RECEIVE).event(OrderStatusChangeEvent.DELIVERY)
                .and()
                .withExternal().source(OrderStatus.WAIT_RECEIVE).target(OrderStatus.FINISH).event(OrderStatusChangeEvent.RECEIVED);
    }
 
    /**
     * 持久化配置
     * 实际使用中，可以配合redis等，进行持久化操作
     * @return
     */
    @Bean
    public DefaultStateMachinePersister persister(){
        return new DefaultStateMachinePersister<>(new StateMachinePersist<Object, Object, Order>() {
            @Override
            public void write(StateMachineContext<Object, Object> context, Order order) throws Exception {
                //此处并没有进行持久化操作
            }
 
            @Override
            public StateMachineContext<Object, Object> read(Order order) throws Exception {
                //此处直接获取order中的状态，其实并没有进行持久化读取操作
                return new DefaultStateMachineContext(order.getStatus(), null, null, null);
            }
        });
    }
}

五、订单状态监听器

package com.caozz.demo2.state.statemachine;


import org.springframework.messaging.Message;
import org.springframework.statemachine.annotation.OnTransition;
import org.springframework.statemachine.annotation.WithStateMachine;
import org.springframework.stereotype.Component;

@Component("orderStateListener")
@WithStateMachine(name = "orderStateMachine")
public class OrderStateListenerImpl{
 
    @OnTransition(source = "WAIT_PAYMENT", target = "WAIT_DELIVER")
    public boolean payTransition(Message<OrderStatusChangeEvent> message) {
        Order order = (Order) message.getHeaders().get("order");
        order.setStatus(OrderStatus.WAIT_DELIVER);
        System.out.println("支付，状态机反馈信息：" + message.getHeaders().toString());
        return true;
    }
 
    @OnTransition(source = "WAIT_DELIVER", target = "WAIT_RECEIVE")
    public boolean deliverTransition(Message<OrderStatusChangeEvent> message) {
        Order order = (Order) message.getHeaders().get("order");
        order.setStatus(OrderStatus.WAIT_RECEIVE);
        System.out.println("发货，状态机反馈信息：" + message.getHeaders().toString());
        return true;
    }
 
    @OnTransition(source = "WAIT_RECEIVE", target = "FINISH")
    public boolean receiveTransition(Message<OrderStatusChangeEvent> message){
        Order order = (Order) message.getHeaders().get("order");
        order.setStatus(OrderStatus.FINISH);
        System.out.println("收货，状态机反馈信息：" + message.getHeaders().toString());
        return true;
    }
}

六、创建订单服务接口

package com.caozz.demo2.state.statemachine;

import java.util.Map;

public interface IOrderService {
    //创建新订单
    Order create();
    //发起支付
    Order pay(int id);
    //订单发货
    Order deliver(int id);
    //订单收货
    Order receive(int id);
    //获取所有订单信息
    Map<Integer, Order> getOrders();
}

七、业务逻辑

package com.caozz.demo2.state.statemachine;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.messaging.Message;
import org.springframework.messaging.support.MessageBuilder;
import org.springframework.statemachine.StateMachine;
import org.springframework.statemachine.persist.StateMachinePersister;
import org.springframework.stereotype.Service;

import java.util.HashMap;
import java.util.Map;

@Service("orderService")
public class OrderServiceImpl implements IOrderService {

    @Autowired
    private StateMachine<OrderStatus, OrderStatusChangeEvent> orderStateMachine;
 
    @Autowired
    private StateMachinePersister<OrderStatus, OrderStatusChangeEvent, Order> persister;
 
    private int id = 1;
    private Map<Integer, Order> orders = new HashMap<>();

    public Order create() {
        Order order = new Order();
        order.setStatus(OrderStatus.WAIT_PAYMENT);
        order.setId(id++);
        orders.put(order.getId(), order);
        return order;
    }

    public Order pay(int id) {
        Order order = orders.get(id);
        System.out.println("线程名称：" + Thread.currentThread().getName() + " 尝试支付，订单号：" + id);
        Message message = MessageBuilder.withPayload(OrderStatusChangeEvent.PAYED).setHeader("order", order).build();
        if (!sendEvent(message, order)) {
            System.out.println("线程名称：" + Thread.currentThread().getName() + " 支付失败, 状态异常，订单号：" + id);
        }
        return orders.get(id);
    }

    public Order deliver(int id) {
        Order order = orders.get(id);
        System.out.println("线程名称：" + Thread.currentThread().getName() + " 尝试发货，订单号：" + id);
        if (!sendEvent(MessageBuilder.withPayload(OrderStatusChangeEvent.DELIVERY).setHeader("order", order).build(), orders.get(id))) {
            System.out.println("线程名称：" + Thread.currentThread().getName() + " 发货失败，状态异常，订单号：" + id);
        }
        return orders.get(id);
    }

    public Order receive(int id) {
        Order order = orders.get(id);
        System.out.println("线程名称：" + Thread.currentThread().getName() + " 尝试收货，订单号：" + id);
        if (!sendEvent(MessageBuilder.withPayload(OrderStatusChangeEvent.RECEIVED).setHeader("order", order).build(), orders.get(id))) {
            System.out.println("线程名称：" + Thread.currentThread().getName() + " 收货失败，状态异常，订单号：" + id);
        }
        return orders.get(id);
    }
 

    public Map<Integer, Order> getOrders() {
        return orders;
    }
 
 
    /**
     * 发送订单状态转换事件
     *
     * @param message
     * @param order
     * @return
     */
    private synchronized boolean sendEvent(Message<OrderStatusChangeEvent> message, Order order) {
        boolean result = false;
        try {
            orderStateMachine.start();
            //尝试恢复状态机状态
            persister.restore(orderStateMachine, order);
            //添加延迟用于线程安全测试
            Thread.sleep(1000);
            result = orderStateMachine.sendEvent(message);
            //持久化状态机状态
            persister.persist(orderStateMachine, order);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            orderStateMachine.stop();
        }
        return result;
    }
}

八、客户端测试

package com.caozz.demo2.state.statemachine;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;

@SpringBootApplication
public class Test {
    public static void main(String[] args) {

        Thread.currentThread().setName("主线程");

        ConfigurableApplicationContext context = SpringApplication.run(Test.class,args);

        IOrderService orderService = (IOrderService)context.getBean("orderService");

        orderService.create();
        orderService.create();

        orderService.pay(1);

        new Thread("客户线程"){
            @Override
            public void run() {
                orderService.deliver(1);
                orderService.receive(1);
            }
        }.start();

        orderService.pay(2);
        orderService.deliver(2);
        orderService.receive(2);

        System.out.println("全部订单状态：" + orderService.getOrders());

    }
}

九、测试结果

线程名称：主线程 尝试支付，订单号：1
支付，状态机反馈信息：{order=订单号：1, 订单状态：WAIT_DELIVER, id=6fa20829-744b-3897-0ad7-22ecbb7703d7, timestamp=1718714853374}
线程名称：主线程 尝试支付，订单号：2
线程名称：客户线程 尝试发货，订单号：1
支付，状态机反馈信息：{order=订单号：2, 订单状态：WAIT_DELIVER, id=b28adbd9-4794-dd50-51a2-d45cda8e455b, timestamp=1718714854474}
线程名称：主线程 尝试发货，订单号：2
发货，状态机反馈信息：{order=订单号：1, 订单状态：WAIT_RECEIVE, id=f80857b0-e664-2704-fff1-f48f2ab039dd, timestamp=1718714854475}
线程名称：客户线程 尝试收货，订单号：1
发货，状态机反馈信息：{order=订单号：2, 订单状态：WAIT_RECEIVE, id=7a3fb443-2a60-b5e6-69d3-cb0594ea47b9, timestamp=1718714855481}
线程名称：主线程 尝试收货，订单号：2
收货，状态机反馈信息：{order=订单号：1, 订单状态：FINISH, id=9589c08e-dc8e-079e-e09f-2cdd0d1dc926, timestamp=1718714856487}
收货，状态机反馈信息：{order=订单号：2, 订单状态：FINISH, id=fa35e7ed-6936-932d-3321-665a21839b4f, timestamp=1718714857491}
全部订单状态：{1=订单号：1, 订单状态：FINISH, 2=订单号：2, 订单状态：FINISH}