SCXML有限状态自动机

• SCXML Parser
• 核心 API，用于 SCXML 文档的解析模块，该 SCXML 文档中的各个元素解析组装成对应的 Java 对象实现。
• DataModel
• 核心 API，用于实现 SCXML 状态机中的数据模型定义，将 SCXML 文档中的 datamodel 元素对应的子元素封装成 Java 对象，供状态机引挚在后续操作中使用。
• Context and Evaluators
• 核心 API，用于实现对 SCXML 状态机中上下文环境的保存和更改，以及对 SCXML 文档中表达式语言（例如 <log expr=”${data.value}” />）的解析操作。
• Executor
• 引挚执行器的实例化模块，核心 API，通过此模块完成一个完整引挚执行器的组装和实例化，并提供引挚启动，停止服务器基础功能模块。
• Triggering Event
• 核心 API，SCXML 引挚中事件的定义实现和执行模块。此模块完成一个外部事件的封装，事件池的组织以及具体的事件作用流程控制。
• Custom Actions
• 高级 API，SCXML 状态机引挚的自定义事件支持。除了 SCXML 标准自带的 <var >、<assign> 和 <log> 等标准事件外，程序人员可以进行自定义事件的开发工作，例如系统平台的构件添加、构件删除操作等，需要程序人员的扩展开发工作。以下代码为 Custom Actions 的使用范例。

<dependencies>
    <dependency>
        <groupId>commons-scxml</groupId>
        <artifactId>commons-scxml</artifactId>
        <version>0.9</version>
    </dependency>

    <dependency>
        <groupId>commons-jexl</groupId>
        <artifactId>commons-jexl</artifactId>
        <version>1.1</version>
    </dependency>

    <dependency>
        <groupId>xalan</groupId>
        <artifactId>xalan</artifactId>
        <version>2.6.0</version>
    </dependency>

</dependencies>

<scxml xmlns="http://www.w3.org/2005/07/scxml"
       version="1.0"
       initialstate="reset">
    <state id="reset">
        <transition event="watch.start"   target="running"/>
    </state>
    <state id="running">
        <transition event="watch.split"   target="paused"/>
        <transition event="watch.stop"    target="stopped"/>
    </state>
    <state id="paused">
        <transition event="watch.unsplit" target="running"/>
        <transition event="watch.stop"    target="stopped"/>
    </state>
    <state id="stopped">
        <transition event="watch.reset"   target="reset"/>
    </state>
</scxml>

import org.apache.commons.scxml.SCXMLListener;
import org.apache.commons.scxml.env.AbstractStateMachine;
import org.apache.commons.scxml.model.ModelException;
import org.apache.commons.scxml.model.State;
import org.apache.commons.scxml.model.Transition;
import org.apache.commons.scxml.model.TransitionTarget;

import java.util.Timer;
import java.util.TimerTask;

public class StopWatch extends AbstractStateMachine {
/**
     * The events for the stop watch.
     */
    public static final String EVENT_START = "watch.start",
            EVENT_STOP = "watch.stop", EVENT_SPLIT = "watch.split",
            EVENT_UNSPLIT = "watch.unsplit", EVENT_RESET = "watch.reset";

    /**
     * The fragments of the elapsed time.
     */
    private int hr, min, sec, fract;

    /**
     * The fragments of the display time.
     */
    private int dhr, dmin, dsec, dfract;

    /**
     * The stopwatch "split" (display freeze).
     */
    private boolean split;

    /**
     * The Timer to keep time.
     */
    private Timer timer;

    /**
     * The display decorations.
     */
    private static final String DELIM = ":", DOT = ".", EMPTY = "", ZERO = "0";

    public StopWatch() throws ModelException {

super(StopWatch.class.getClassLoader().getResource("stopwatch.xml"));
        getEngine().addListener(getEngine().getStateMachine(), new EntryListener());
        System.out.println(StopWatch.class.getClassLoader().getResource("stopwatch.xml"));
    }

public void reset() {

hr = min = sec = fract = dhr = dmin = dsec = dfract = 0;
        split = false;
    }

public void running() {

split = false;
        if (timer == null) {
timer = new Timer(true);
            timer.scheduleAtFixedRate(new TimerTask() {
@Override
                public void run() {
                    increment();
                }
            }, 100, 100);
        }
    }

public void paused() {

split = true;
    }

public void stopped() {

timer.cancel();
        timer = null;
    }

public String getDisplay() {

        String padhr = dhr > 9 ? EMPTY : ZERO;
        String padmin = dmin > 9 ? EMPTY : ZERO;
        String padsec = dsec > 9 ? EMPTY : ZERO;
        return new StringBuffer().append(padhr).append(dhr).append(DELIM).
                append(padmin).append(dmin).append(DELIM).append(padsec).
                append(dsec).append(DOT).append(dfract).toString();
    }

public String getCurrentState() {

return ((State)getEngine().getCurrentStatus().getStates().iterator().next()).getId();
    }

private void increment() {
if (fract < 9) {
fract++;
        } else {
fract = 0;
            if (sec < 59) {
sec++;
            } else {
sec = 0;
                if (min < 59) {
min++;
                } else {
min = 0;
                    if (hr < 99) {
hr++;
                    } else {
hr = 0; //wrap
                    }
                }
            }
        }
if (!split) {
dhr = hr;
            dmin = min;
            dsec = sec;
            dfract = fract;
        }
    }

/**
     * A SCXMLListener that is only concerned about &quot;onentry&quot;
     * notifications.
     */
    protected class EntryListener implements SCXMLListener {
public void onEntry(final TransitionTarget entered) {
            System.out.println("Current State:"+entered.getId());
        }
public void onTransition(final TransitionTarget from,
                                 final TransitionTarget to, final Transition transition) {
// nothing to do
        }
public void onExit(final TransitionTarget exited) {
// nothing to do
        }

    }
}

public static void main(String[] args) throws ModelException {

    StopWatch stopWatch = new StopWatch();
    Scanner input=new Scanner(System.in);
    System.out.println("event: watch.start watch.stop watch.reset watch.split watch.unsplit");
    while(true){
        String event=input.nextLine();
        if(event.trim()!=null&&!event.trim().equals("")){
if(event.equals("exit")) break;
            else{
                stopWatch.fireEvent(event);
                System.out.println(stopWatch.getCurrentState());
                System.out.print(stopWatch.getDisplay());
            }
        }
    }

}