一直以来，总觉得ssm不够灵活，主要原因是没找到为状态机指定状态的方式，也就意味着状态机引擎实例必须要跟对应的业务数据一起持久化，虽然ssm提供了多重持久化的方式，依然觉得有点不爽。
最近又回过头去啃了下文档和源码，无意中在AbstractStateMachine类中看到了setCurrentState方法，如下：
void setCurrentState(State state, Message message, Transition transition, boolean exit, StateMachine stateMachine) {
this.setCurrentState(state, message, transition, exit, stateMachine, (Collection)null, (Collection)null);
}
void setCurrentState(State state, Message message, Transition transition, boolean exit, StateMachine stateMachine, Collection> sources, Collection> targets) {
this.setCurrentStateInternal(state, message, transition, exit, stateMachine, sources, targets);
}
private void setCurrentStateInternal(State state, Message message, Transition transition, boolean exit, StateMachine stateMachine, Collection> sources, Collection> targets) {
...
}
emmm，貌似有门儿，于是做了以下尝试。
搭个项目框架
为了简单，用springboot基于maven搭了个简单的项目(http://start.spring.io)
pom.xml
4.0.0
org.springframework.boot
spring-boot-starter-parent
2.1.8.RELEASE
com.example
demo
0.0.1-SNAPSHOT
demo
Demo project for Spring Boot
1.8
2.1.3.RELEASE
org.springframework.boot
spring-boot-starter
org.springframework.statemachine
spring-statemachine-core
${spring-statemachine.version}
org.springframework.boot
spring-boot-starter-test
test
org.projectlombok
lombok
1.18.8
org.springframework.boot
spring-boot-maven-plugin
可以看到，只需要引入spring-statemachine-core就可以了，当然夹带点私货，顺手扔上去了lombok。
States & Events
package com.example.demo;
public enum States {
SI, S1, S2, S3;
}
package com.example.demo;
public enum Events {
E1, E2, E3;
}
spring statemachine config
定义了一些configure & listener
package com.example.demo;
import org.springframework.context.annotation.Configuration;
import org.springframework.messaging.Message;
import org.springframework.statemachine.config.EnableStateMachine;
import org.springframework.statemachine.config.EnumStateMachineConfigurerAdapter;
import org.springframework.statemachine.config.builders.StateMachineConfigurationConfigurer;
import org.springframework.statemachine.config.builders.StateMachineStateConfigurer;
import org.springframework.statemachine.config.builders.StateMachineTransitionConfigurer;
import org.springframework.statemachine.listener.StateMachineListener;
import org.springframework.statemachine.listener.StateMachineListenerAdapter;
import org.springframework.statemachine.state.State;
import org.springframework.statemachine.transition.Transition;
import java.util.EnumSet;
import java.util.Optional;
@Configuration
@EnableStateMachine
public class StateMachineConfig
extends EnumStateMachineConfigurerAdapter {
@Override
public void configure(StateMachineConfigurationConfigurer config)
throws Exception {
config
.withConfiguration()
.autoStartup(true)
.listener(listener());
}
@Override
public void configure(StateMachineStateConfigurer states)
throws Exception {
states
.withStates()
.initial(States.SI)
.states(EnumSet.allOf(States.class));
}
@Override
public void configure(StateMachineTransitionConfigurer transitions)
throws Exception {
transitions
.withExternal()
.source(States.SI).target(States.S1).event(Events.E1)
.and()
.withExternal()
.source(States.S1).target(States.S2).event(Events.E2)
.and()
.withExternal()
.source(States.S2).target(States.S3).event(Events.E3);
}
private StateMachineListener listener() {
return new StateMachineListenerAdapter() {
@Override
public void transition(Transition transition) {
System.out.println("move from:{" + ofNullableState(transition.getSource()) + "} " +
"to:{" + ofNullableState(transition.getTarget()) + "}");
}
@Override
public void stateChanged(State from, State to) {
if (null != from) {
System.out.println("State change from " + from.getId() + " to " + to.getId());
} else {
System.out.println("State change to " + to.getId());
}
}
@Override
public void eventNotAccepted(Message event) {
System.err.println("event not accepted: {" + event + "}");
}
private Object ofNullableState(State s) {
return Optional.ofNullable(s)
.map(State::getId)
.orElse(null);
}
};
}
/* @Bean
public StateMachineListener listener() {
return new StateMachineListenerAdapter() {
@Override
public void stateChanged(State from, State to) {
System.out.println("State change to " + to.getId());
}
};
}*/
}
Stringboot Application
package com.example.demo;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.statemachine.StateMachine;
@SpringBootApplication
public class DemoApplication implements CommandLineRunner {
public static void main(String[] args) {
SpringApplication.run(DemoApplication.class, args);
}
@Autowired
private StateMachine stateMachine;
@Override
public void run(String... args) throws Exception {
stateMachine.sendEvent(Events.E1);
stateMachine.sendEvent(Events.E2);
}
}
执行结果
mvn clean install
Java -jar *.jar
move from:{null} to:{SI}
State change to SI
2019-09-17 23:10:14.374 INFO 71833 --- [ main] o.s.s.support.LifecycleObjectSupport : started S3 SI S2 S1 / SI / uuid=eb612bb8-d97f-4505-b8af-4106320b3073 / id=null
move from:{SI} to:{S1}
State change from SI to S1
move from:{S1} to:{S2}
State change from S1 to S2
可以看到，可以通过sendEvent来触发状态机引擎的状态流转
setCurrentState
上面只是一个常规的demo，那么怎么直接设置当前状态呢？
还是回到上面的AbstractStateMachine类中setCurrentState方法定义：
void setCurrentState(State state, Message message, Transition transition, boolean exit, StateMachine stateMachine)
State state：需要设置的状态
Message message：需要携带的message，这里先不用
Transition transition：对应节点，可以先不用，毕竟还需要构造
boolean exit：？是否可以exit，默认走false
StateMachine stateMachine：具体的状态机引擎实例
应该是需要提供写一个工具类，屏蔽掉上游调用的复杂度。而SpringStateMachine中本身就提供了一个工具类StateMachineUtils，直接基于它扩展吧，毕竟很多上下文的东西构造起来还是挺麻烦。
StateMachineUtils工具类
package org.springframework.statemachine.support;
import org.springframework.statemachine.StateMachine;
import org.springframework.statemachine.state.State;
public abstract class MyStateMachineUtils extends StateMachineUtils {
public static void setCurrentState(StateMachine stateMachine, S state) {
if (stateMachine instanceof AbstractStateMachine) {
setCurrentState((AbstractStateMachine) stateMachine, state);
System.out.println("StateMachine Current:" + stateMachine);
} else {
throw new IllegalArgumentException("Provided StateMachine is not a valid type");
}
}
public static void setCurrentState(AbstractStateMachine stateMachine, S state) {
stateMachine.setCurrentState(findState(stateMachine, state), null, null, false, stateMachine);
}
private static State findState(AbstractStateMachine stateMachine, S stateId) {
for (State state : stateMachine.getStates()) {
if (state.getId() == stateId) {
return state;
}
}
throw new IllegalArgumentException("Specified State ID is not valid");
}
}
注意：
1、这里的包名是org.springframework.statemachine.support，因为setCurrentState是default的scope，不放在同一个包里无法直接操作
2、这里findState是从stateMachine实例中获取目标state
修改DemoApplication
@Override
public void run(String... args) throws Exception {
// stateMachine.sendEvent(Events.E1);
MyStateMachineUtils.setCurrentState(stateMachine,States.S1);
stateMachine.sendEvent(Events.E2);
}
执行下看结果：
move from:{null} to:{SI}
State change to SI
2019-09-17 23:21:14.788 INFO 72337 --- [ main] o.s.s.support.LifecycleObjectSupport : started S1 S3 SI S2 / SI / uuid=801118a8-0115-48e1-95e7-a8ba67e5d30f / id=null
State change from SI to S1
StateMachine Current:S1 S3 SI S2 / S1 / uuid=801118a8-0115-48e1-95e7-a8ba67e5d30f / id=null
move from:{S1} to:{S2}
State change from S1 to S2
可以看到，直接把stateMachine的状态从SI迁移到了S1，done！
注意：这里如果spring-statemachine.version=2.1.3.RELEASE是正常的，但是如果是使用3.0.0.M1版本，则状态一直未生效，应该是新版本还有缺陷。