ssssssss-team/spider-flow · error · ScriptException

_eval必须要有一个参数

Error message

_eval必须要有一个参数

What it means

Guard inside ScriptManager.eval: when the expression engine calls the built-in _eval function, exactly one argument (the script text to evaluate) is required. The error fires when args is null or its length differs from 1, i.e. a spider-flow expression invoked _eval with zero or multiple arguments, so the Nashorn script cannot be built.

Solutions

1. Pass exactly one argument to _eval in the expression, e.g. _eval('return 1+1').
2. If dynamic argument counts are needed, build the script string first and pass it as a single argument.
3. Check the flow variable feeding the argument — a missing variable can collapse the argument list to zero arguments.

When it happens

Trigger: Thrown at spider-flow-core/src/main/java/org/spiderflow/core/script/ScriptManager.java:102 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of ssssssss-team/spider-flow@c799cca99c (2026-09-08). Data as JSON: /api/errors/1b37c16d9e2c8d7c. Report an issue: GitHub.

Appendix: source

Thrown at spider-flow-core/src/main/java/org/spiderflow/core/script/ScriptManager.java:102

    }

    public static boolean containsFunction(String functionName){
        try {
            lock.readLock().lock();
            return functions.contains(functionName);
        } finally {
            lock.readLock().unlock();
        }
    }

    public static void validScript(String functionName,String parameters,String script) throws Exception {
        new ScriptEngineManager().getEngineByName("nashorn").eval(concatScript(functionName,parameters,script));
    }

    public static Object eval(ExpressionTemplateContext context, String functionName, Object ... args) throws ScriptException, NoSuchMethodException {
        if("_eval".equals(functionName)){
            if(args == null || args.length != 1){
                throw new ScriptException("_eval必须要有一个参数");
            }else{
                return ExpressionTemplate.create(args[0].toString()).render(context);
            }
        }
        if(scriptEngine == null){
            throw new NoSuchMethodException(functionName);
        }
        try{
            lock.readLock().lock();
            return convertObject(((Invocable) scriptEngine).invokeFunction(functionName, args));
        } finally{
            lock.readLock().unlock();
        }
    }

    private static Object convertObject(Object object){
        if(object instanceof ScriptObjectMirror){
            ScriptObjectMirror mirror = (ScriptObjectMirror) object;

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