Apache Commons SCXML - 找不到 JexlContext

Question

我是 SCXML 新手，甚至无法启动最简单的应用程序。当我尝试启动它时，出现以下异常。但我在类路径上有该类的库 commons-scxml-0.9.jar 。有什么想法吗？

Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/commons/jexl/JexlContext
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClassCond(ClassLoader.java:631)
at java.lang.ClassLoader.defineClass(ClassLoader.java:615)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:283)
at java.net.URLClassLoader.access$000(URLClassLoader.java:58)
at java.net.URLClassLoader$1.run(URLClassLoader.java:197)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
at org.apache.commons.scxml.env.AbstractStateMachine.<init>(AbstractStateMachine.java:103)
at main.StateMachineImpl.<init>(StateMachineImpl.java:8)
at main.Main.main(Main.java:6)

Caused by: java.lang.ClassNotFoundException: org.apache.commons.jexl.JexlContext
at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
... 15 more

这是代码：

Main class

public class Main {
    public static void main(String[] args) {
        StateMachineImpl stateMachineImpl = new StateMachineImpl();
        stateMachineImpl.fireEvent(Event.START.getEvent());
        stateMachineImpl.fireEvent(Event.STOP.getEvent());
    }
}

Event

public enum Event {

    START("event.start"), STOP("event.stop");

    private String event;

    private Event(String event) {
        this.event = event;
    }

    public String getEvent() {
        return event;
    }

    public void setEvent(String event) {
        this.event = event;
    }

}

StateMachineImpl

public class StateMachineImpl extends AbstractStateMachine {

    public StateMachineImpl() {
        super(StateMachineImpl.class.getClassLoader().getResource("state-machine-cfg.xml"));
    }

    public void off() {
        System.out.println("StateMachine is OFF");
    }

    public void running() {
        System.out.println("StateMachine is RUNNING");
    }

}

state-machine-cfg.xml

<?xml version="1.0" encoding="UTF-8"?>
<scxml xmlns="http://www.w3.org/2005/07/scxml" version="1.0"
    initialstate="off">

    <state id="off">
        <transition event="event.start" target="running" />
    </state>

    <state id="running">
        <transition event="event.stop" target="off" />
    </state>

</scxml>

编辑 - 解决方案： 我必须添加额外的依赖项（我认为它们会由 Maven 自动加载）。

pom.xml 依赖项

<dependency>
    <groupId>commons-scxml</groupId>
    <artifactId>commons-scxml</artifactId>
    <version>0.9</version>
</dependency>
<dependency>
    <groupId>commons-logging</groupId>
    <artifactId>commons-logging</artifactId>
    <version>1.1.1</version>
</dependency>
<dependency>
    <groupId>commons-jexl</groupId>
    <artifactId>commons-jexl</artifactId>
    <version>1.1</version>
</dependency>
<dependency>
    <groupId>xalan</groupId>
    <artifactId>xalan</artifactId>
    <version>2.7.1</version>
</dependency>

Answer 1

添加 commons-jexl.jar 也到 CLASSPATH 中。根据项目 pom. xml 在 0.9 版本中，您还需要（不包括传递依赖项）：

• commons-logging
• commons-digester
• commons-beanutils
• commons-el

Answer 2

所有 SCXML 依赖项 jar 都可以在这里找到：

http://commons.apache.org/scxml/dependency。 html

Answer 3

在问题提出近 12 年后我又遇到了同样的问题。答案不适用于当前版本的 common-scxml2。我找到了添加当前需要的 jexl3 版本的灵魂。

<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-jexl3</artifactId>
    <version>3.3</version>
</dependency>