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<S, E> state, Message<E> message, Transition<S, E> transition, boolean exit, StateMachine<S, E> stateMachine) {
this.setCurrentState(state, message, transition, exit, stateMachine, (Collection)null, (Collection)null);
}
void setCurrentState(State<S, E> state, Message<E> message, Transition<S, E> transition, boolean exit, StateMachine<S, E> stateMachine, Collection<State<S, E>> sources, Collection<State<S, E>> targets) {
this.setCurrentStateInternal(state, message, transition, exit, stateMachine, sources, targets);
}
private void setCurrentStateInternal(State<S, E> state, Message<E> message, Transition<S, E> transition, boolean exit, StateMachine<S, E> stateMachine, Collection<State<S, E>> sources, Collection<State<S, E>> 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
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.1.8.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.example</groupId>
<artifactId>demo</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>demo</name>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>1.8</java.version>
<spring-statemachine.version>2.1.3.RELEASE</spring-statemachine.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.statemachine</groupId>
<artifactId>spring-statemachine-core</artifactId>
<version>${spring-statemachine.version}</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.18.8</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
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<States, Events> {
@Override
public void configure(StateMachineConfigurationConfigurer<States, Events> config)
throws Exception {
config
.withConfiguration()
.autoStartup(true)
.listener(listener());
}
@Override
public void configure(StateMachineStateConfigurer<States, Events> states)
throws Exception {
states
.withStates()
.initial(States.SI)
.states(EnumSet.allOf(States.class));
}
@Override
public void configure(StateMachineTransitionConfigurer<States, Events> 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<States, Events> listener() {
return new StateMachineListenerAdapter<States, Events>() {
@Override
public void transition(Transition<States, Events> transition) {
System.out.println("move from:{" + ofNullableState(transition.getSource()) + "} " +
"to:{" + ofNullableState(transition.getTarget()) + "}");
}
@Override
public void stateChanged(State<States, Events> from, State<States, Events> 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<Events> 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<States, Events> listener() {
return new StateMachineListenerAdapter<States, Events>() {
@Override
public void stateChanged(State<States, Events> from, State<States, Events> 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<States, Events> 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<S, E> state, Message<E> message, Transition<S, E> transition, boolean exit, StateMachine<S, E> stateMachine)
State<S, E> state：需要设置的状态
Message<E> message：需要携带的message，这里先不用
Transition<S, E> 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<S, E> 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 <S, E> void setCurrentState(StateMachine<S, E> stateMachine, S state) {
if (stateMachine instanceof AbstractStateMachine) {
setCurrentState((AbstractStateMachine<S, E>) stateMachine, state);
System.out.println("StateMachine Current:" + stateMachine);
} else {
throw new IllegalArgumentException("Provided StateMachine is not a valid type");
}
}
public static <S, E> void setCurrentState(AbstractStateMachine<S, E> stateMachine, S state) {
stateMachine.setCurrentState(findState(stateMachine, state), null, null, false, stateMachine);
}
private static <S, E> State<S, E> findState(AbstractStateMachine<S, E> stateMachine, S stateId) {
for (State<S, E> 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。