java环境运行python脚本：Cannot invoke "javax.script.ScriptEngine.getFactory()" because "scriptEngine" is null

在用Liteflow规则引擎中，用到了python脚本，发现ide启动时脚本正常运行，到了线上环境就报异常。经过调试发现 scriptEngineManager.getEngineByName("python");获取到的engine为null。

public ScriptExecutor init() throws ScriptException {
    ScriptEngineManager scriptEngineManager = new ScriptEngineManager();
    scriptEngine = scriptEngineManager.getEngineByName(scriptEngineName());
    if (scriptEngine == null) {
        log.error("load scriptEngine[{}] error: scriptEngine is null!", scriptEngineName());
        throw new ScriptException("load scriptEngine[" + scriptEngineName() + "] error, scriptEngine is null !");
    }
    return this;
}

正好刚注册了个GhatGpt，于是直接来问一下：

根据ChatGpt提示尝试新增python.home，指定 jython-standalone-2.7.3.jar的绝对路径可以解决。

由于应用打好Jar包里面已经有了jython-standalone依赖，不想再在部署的时候额外拿个jar包进去，所以又做了点改动：应用启动时，判断当jar包运行时，从BOOT-INF/lib下将jython拷贝出来，并设置python.home:

@Slf4j
@Component
public class ApplicationInitRunner implements CommandLineRunner {

    @Value("${python.home:}")
    private String pythonHome;

    @Override
    public void run(String... args)  {
        if (StringUtils.isNotBlank(pythonHome)) {
            //复制jython包到python home
            boolean copyed = JarExtractor.copyJython2PythonHome(pythonHome);
            if(copyed){
                System.setProperty("python.import.site","false");
                System.setProperty("python.home",pythonHome);
            }
        }
    }

}

以下拷贝jar包代码片段：

final static String jythonName = "jython-standalone-2.7.3.jar";

/**
 * 判断是否从jar包运行
 * @return
 */
public static boolean isRunningFromJar() {
    URL resource = JarExtractor.class.getResource("");
    return resource != null && resource.getProtocol().equals("jar");
}

public static boolean copyJython2PythonHome(String pythonHome){
    return copyJar(jythonName,pythonHome);
}

/**
 * 拷贝包里的依赖到指定目录
 * @param jarName
 * @param targetPath
 */
public static boolean copyJar(String jarName,String targetPath){
    if(isRunningFromJar()){
        ClassLoader defaultClassLoader = ClassUtils.getDefaultClassLoader();
        try (InputStream inputStream = defaultClassLoader.getResourceAsStream("BOOT-INF/lib/"+jarName)) {
            if(inputStream != null){
                log.info("CopyJar:{} -> {}",jarName,targetPath);
                write2File(inputStream,targetPath);
                return true;
            }
        } catch (Exception e) {
            log.error("jar {} -> {} copy error: {}",jarName,e.getMessage());
        }
    }
    return false;
}