import org.apache.nifi.components.AllowableValue; //导入依赖的package包/类
/**
 * This method creates all resources needed for the script processor to function, such as script engines,
 * script file reloader threads, etc.
 */
public void createResources() {
    descriptors = new ArrayList<>();
    // The following is required for JRuby, should be transparent to everything else.
    // Note this is not done in a ScriptEngineConfigurator, as it is too early in the lifecycle. The
    // setting must be there before the factories/engines are loaded.
    System.setProperty("org.jruby.embed.localvariable.behavior", "persistent");

    // Create list of available engines
    ScriptEngineManager scriptEngineManager = new ScriptEngineManager();
    List<ScriptEngineFactory> scriptEngineFactories = scriptEngineManager.getEngineFactories();
    if (scriptEngineFactories != null) {
        scriptEngineFactoryMap = new HashMap<>(scriptEngineFactories.size());
        List<AllowableValue> engineList = new LinkedList<>();
        for (ScriptEngineFactory factory : scriptEngineFactories) {
            engineList.add(new AllowableValue(factory.getLanguageName()));
            scriptEngineFactoryMap.put(factory.getLanguageName(), factory);
        }

        // Sort the list by name so the list always looks the same.
        Collections.sort(engineList, (o1, o2) -> {
            if (o1 == null) {
                return o2 == null ? 0 : 1;
            }
            if (o2 == null) {
                return -1;
            }
            return o1.getValue().compareTo(o2.getValue());
        });

        AllowableValue[] engines = engineList.toArray(new AllowableValue[engineList.size()]);

        SCRIPT_ENGINE = new PropertyDescriptor.Builder()
                .name("Script Engine")
                .required(true)
                .description("The engine to execute scripts")
                .allowableValues(engines)
                .defaultValue(engines[0].getValue())
                .required(true)
                .expressionLanguageSupported(false)
                .build();
        descriptors.add(SCRIPT_ENGINE);
    }

    descriptors.add(ScriptingComponentUtils.SCRIPT_FILE);
    descriptors.add(ScriptingComponentUtils.SCRIPT_BODY);
    descriptors.add(ScriptingComponentUtils.MODULES);

    isInitialized.set(true);
}