1、多個狀态機的搞法
在實際的企業應用中,基本不可能隻有一個狀态機流程在跑,比如訂單,肯定是很多個訂單在運作,每個訂單都有自己的訂單狀态機流程,但上一章的例子,大家可以試一下,當執行到一個狀态時,再次重新整理頁面,不會有任何日志出現,當一個狀态流程執行到某個狀态,再次執行這個狀态,是不會有任何輸出的,因為狀态機的機制是隻有在狀态切換的時候才會事件(event)觸發,是以我們這一章講多個狀态機的并行執行。
首先,靠上一章例子裡面的手打定制一個StateMachineConfig的做法,就隻能是有一個狀态機流程制霸整個項目,這種霸道的做法肯定是不行啦,要想多個狀态機流程并行,那麼就要請builder出場了,看代碼:
private final static String MACHINEID = "orderMachine";
public StateMachine<OrderStates, OrderEvents> build(BeanFactory beanFactory) throws Exception {
StateMachineBuilder.Builder<OrderStates, OrderEvents> builder = StateMachineBuilder.builder();
System.out.println("建構訂單狀态機");
builder.configureConfiguration()
.withConfiguration()
.machineId(MACHINEID)
.beanFactory(beanFactory);
builder.configureStates()
.withStates()
.initial(OrderStates.UNPAID)
.states(EnumSet.allOf(OrderStates.class));
builder.configureTransitions()
.withExternal()
.source(OrderStates.UNPAID).target(OrderStates.WAITING_FOR_RECEIVE)
.event(OrderEvents.PAY).action(action())
.and()
.withExternal()
.source(OrderStates.WAITING_FOR_RECEIVE).target(OrderStates.DONE)
.event(OrderEvents.RECEIVE);
return builder.build();
}
有沒有似曾相識的感覺,裡面描述訂單狀态機的初始狀态,狀态機的流程代碼和StateMachineConfig幾乎是一樣的,但是都配置在StateMachineBuilder裡面
StateMachineBuilder.Builder<OrderStates, OrderEvents> builder = StateMachineBuilder.builder();
這是完整的builder類代碼:
import java.util.EnumSet;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.context.annotation.Bean;
import org.springframework.statemachine.StateContext;
import org.springframework.statemachine.StateMachine;
import org.springframework.statemachine.action.Action;
import org.springframework.statemachine.config.StateMachineBuilder;
import org.springframework.stereotype.Component;
@Component
public class OrderStateMachineBuilder {
private final static String MACHINEID = "orderMachine";
/**
* 建構狀态機
*
* @param beanFactory
* @return
* @throws Exception
*/
public StateMachine<OrderStates, OrderEvents> build(BeanFactory beanFactory) throws Exception {
StateMachineBuilder.Builder<OrderStates, OrderEvents> builder = StateMachineBuilder.builder();
System.out.println("建構訂單狀态機");
builder.configureConfiguration()
.withConfiguration()
.machineId(MACHINEID)
.beanFactory(beanFactory);
builder.configureStates()
.withStates()
.initial(OrderStates.UNPAID)
.states(EnumSet.allOf(OrderStates.class));
builder.configureTransitions()
.withExternal()
.source(OrderStates.UNPAID).target(OrderStates.WAITING_FOR_RECEIVE)
.event(OrderEvents.PAY).action(action())
.and()
.withExternal()
.source(OrderStates.WAITING_FOR_RECEIVE).target(OrderStates.DONE)
.event(OrderEvents.RECEIVE);
return builder.build();
}
@Bean
public Action<OrderStates, OrderEvents> action() {
return new Action<OrderStates, OrderEvents>() {
@Override
public void execute(StateContext<OrderStates, OrderEvents> context) {
System.out.println(context);
}
};
}
}
在完整的代碼裡面我們看到有個東西沒講,那就是MACHINEID,在builder的配置代碼裡面,有這麼一段
builder.configureConfiguration()
.withConfiguration()
.machineId(MACHINEID)
.beanFactory(beanFactory);
machineId是狀态機的配置類和事件實作類的關聯,和它關聯的是OrderEventConfig,代碼如下:
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.messaging.Message;
import org.springframework.statemachine.annotation.OnTransition;
import org.springframework.statemachine.annotation.WithStateMachine;
@WithStateMachine(id="orderMachine")
public class OrderEventConfig {
private Logger logger = LoggerFactory.getLogger(getClass());
/**
* 目前狀态UNPAID
*/
@OnTransition(target = "UNPAID")
public void create() {
logger.info("---訂單建立,待支付---");
}
......
}
這個後面的内容和上一章的OrderSingleEventConfig一模一樣,但在類的上面注解了這一句:
@WithStateMachine(id="orderMachine")
這個id對應的就是OrderStateMachineBuilder 裡面的MACHINEID,被builder寫到.machineId(MACHINEID)裡面。這樣,OrderStateMachineBuilder對應上一章的StateMachineConfig多個狀态機的實作版本,OrderEventConfig對應上一章的OrderSingleEventConfig,基本一樣,隻是和OrderStateMachineBuilder通過machineid做了關聯。
現在我們來看怎麼用上它。在controller裡面引用這個類:
@Autowired
private OrderStateMachineBuilder orderStateMachineBuilder;
然後使用它
@RequestMapping("/testOrderState")
public void testOrderState(String orderId) throws Exception {
StateMachine<OrderStates, OrderEvents> stateMachine = orderStateMachineBuilder.build(beanFactory);
// 建立流程
stateMachine.start();
// 觸發PAY事件
stateMachine.sendEvent(OrderEvents.PAY);
// 觸發RECEIVE事件
stateMachine.sendEvent(OrderEvents.RECEIVE);
// 擷取最終狀态
System.out.println("最終狀态:" + stateMachine.getState().getId());
}
這其實就是每次請求testOrderState就會生成一個新的statemachine,是以每次重新整理testOrderState請求都會看到日志顯示:
建構訂單狀态機
orderMachine
2019-05-03 19:24:23.734 INFO 11752 --- [nio-9991-exec-1] tConfig$$EnhancerBySpringCGLIB$$29e58541 : ---訂單建立,待支付---
2019-05-03 19:24:23.754 INFO 11752 --- [nio-9991-exec-1] o.s.s.support.LifecycleObjectSupport : started org.springframework.statemachine.support.DefaultStateMachineExecutor@133d52dd
2019-05-03 19:24:23.755 INFO 11752 --- [nio-9991-exec-1] o.s.s.support.LifecycleObjectSupport : started UNPAID DONE WAITING_FOR_RECEIVE / UNPAID / uuid=52b44103-22af-49cc-a645-3aab29212a9e / id=orderMachine
DefaultStateContext [stage=TRANSITION, message=GenericMessage [payload=PAY, headers={id=ed826b85-e069-9a5e-34a1-d78454183143, timestamp=1556882663765}], messageHeaders={id=ade4055c-9b59-6498-501e-0e2a8cfe04b4, _sm_id_=52b44103-22af-49cc-a645-3aab29212a9e, timestamp=1556882663767}, extendedState=DefaultExtendedState [variables={}], transition=AbstractTransition [source=ObjectState [getIds()=[UNPAID], getClass()=class org.springframework.statemachine.state.ObjectState, hashCode()=1027927242, toString()=AbstractState [id=UNPAID, pseudoState=org.springframework.statemachine.state.DefaultPseudoState@4b05dcc, deferred=[], entryActions=[], exitActions=[], stateActions=[], regions=[], submachine=null]], target=ObjectState [getIds()=[WAITING_FOR_RECEIVE], getClass()=class org.springframework.statemachine.state.ObjectState, hashCode()=422378, toString()=AbstractState [id=WAITING_FOR_RECEIVE, pseudoState=null, deferred=[], entryActions=[], exitActions=[], stateActions=[], regions=[], submachine=null]], kind=EXTERNAL, guard=null], stateMachine=UNPAID DONE WAITING_FOR_RECEIVE / UNPAID / uuid=52b44103-22af-49cc-a645-3aab29212a9e / id=orderMachine, source=null, target=null, sources=null, targets=null, exception=null]
傳遞的參數:null
2019-05-03 19:24:23.775 INFO 11752 --- [nio-9991-exec-1] tConfig$$EnhancerBySpringCGLIB$$29e58541 : ---使用者完成支付,待收貨---
傳遞的參數:null
傳遞的參數:null
2019-05-03 19:24:23.782 INFO 11752 --- [nio-9991-exec-1] tConfig$$EnhancerBySpringCGLIB$$29e58541 : ---使用者已收貨,訂單完成---
最終狀态:DONE
這和之前執行testSingleOrderState是不一樣的,testSingleOrderState隻有第一次會有日志打出,再執行就沒有日志出來了,而testOrderState因為每次都build一個新的statemachine,是以每次都會顯示日志出來,這樣就能保證每個訂單都可以為它build一個新的statemachine,就解決了多個狀态機并行執行的問題了。
雖然多個狀态機的問題解決了,但是對于實際的企業應用而言,還是有問題。這種簡單粗暴的,來一個請求就新增一個狀态機的搞法很不經濟,而且狀态機也不是越多越好,而應該是和業務對象一一對應才行,比如訂單,就是一個訂單一個狀态機,而不是每次訂單變化就build的一個。這個問題就用到了狀态機的持久化,我們下一章就談談持久化問題。
2、有個坑
EventConfig類的@WithStateMachine注解有兩個參數可用
public @interface WithStateMachine {
/**
* The name of a state machine bean which annotated bean should be associated.
* Defaults to {@code stateMachine}
*
* @return the state machine bean name
*/
String name() default StateMachineSystemConstants.DEFAULT_ID_STATEMACHINE;
/**
* The id of a state machine which annotated bean should be associated.
*
* @return the state machine id
* @see StateMachine#getId()
*/
String id() default "";
}
我們在上面是用id來關聯StateMachineBuilder和EventConfig的,用name是無效的,但這個id是spring-statemachine-starter,2.x版本才有,在1.x版本裡面,隻有name參數,用name參數StateMachineBuilder和EventConfig關聯不上,也就是在builder裡面狀态變化,eventConfig裡面并不會同步觸發事件,請大家确認使用的是2.x的版本,這都是我血與淚的忠告。
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