使用Spring StateMachine框架实现状态机

• 根据上面所述的订单需求场景定义状态和事件枚举，具体如下：

public enum States {

UNPAID, // 待支付

WAITING_FOR_RECEIVE, // 待收货

DONE // 结束

}

public enum Events {

PAY, // 支付

RECEIVE // 收货

}

其中共有三个状态（待支付、待收货、结束）以及两个引起状态迁移的事件（支付、收货），其中支付事件PAY会触发状态从待支付UNPAID状态到待收货WAITING_FOR_RECEIVE状态的迁移，而收货事件RECEIVE会触发状态从待收货WAITING_FOR_RECEIVE状态到结束DONE状态的迁移。

• 创建状态机配置类：

@Configuration

@EnableStateMachine

public class StateMachineConfig extends EnumStateMachineConfigurerAdapter<States, Events> {

private Logger logger = LoggerFactory.getLogger(getClass());

@Override

public void configure(StateMachineStateConfigurer<States, Events> states)

throws Exception {

states

.withStates()

.initial(States.UNPAID)

.states(EnumSet.allOf(States.class));

}

@Override

public void configure(StateMachineTransitionConfigurer<States, Events> transitions)

throws Exception {

transitions

.withExternal()

.source(States.UNPAID).target(States.WAITING_FOR_RECEIVE)

.event(Events.PAY)

.and()

.withExternal()

.source(States.WAITING_FOR_RECEIVE).target(States.DONE)

.event(Events.RECEIVE);

}

@Override

public void configure(StateMachineConfigurationConfigurer<States, Events> config)

throws Exception {

config

.withConfiguration()

.listener(listener());

}

@Bean

public StateMachineListener<States, Events> listener() {

return new StateMachineListenerAdapter<States, Events>() {

@Override

public void transition(Transition<States, Events> transition) {

if(transition.getTarget().getId() == States.UNPAID) {

logger.info(“订单创建，待支付”);

return;

}

if(transition.getSource().getId() == States.UNPAID

&& transition.getTarget().getId() == States.WAITING_FOR_RECEIVE) {

logger.info(“用户完成支付，待收货”);

return;

}

if(transition.getSource().getId() == States.WAITING_FOR_RECEIVE

&& transition.getTarget().getId() == States.DONE) {

logger.info(“用户已收货，订单完成”);

return;

}

}

};

}

}

在该类中定义了较多配置内容，下面对这些内容一一说明：

• @EnableStateMachine注解用来启用Spring StateMachine状态机