Call js methods from java

Question

I have requirement to execute javascript method (which does some reporting and dump a PDF file) from java class.

Facing issue on how to load the context path in java method and call js method directly from java.

Eg. I need the context path of js file like /webapp/js/orn/workflow/Engine.js same as we get from browser in my java class :- ocm\src\main\java\com\interra\orion\util\workflow\ScriptEngineUtil.java

Any thoughts on how to proceed, I tried using Rhino but got struck on how to context path.

Possible duplicate of [Call external javascript functions from java code](https://stackoverflow.com/questions/22856279/call-external-javascript-functions-from-java-code) — 31piy, Apr 12 '18 at 05:54
`new ScriptEngineManager().getEngineByName("ECMAScript").eval("function a() {return 'hello world';} print(a());");` — Aniket Sahrawat, Apr 12 '18 at 05:57
I want to execute method of javascript file present in webapp directory. — shrutika ukey, Apr 12 '18 at 06:02

score 0 · Accepted Answer · answered Apr 12 '18 at 07:16

The available answers provide enough information to call javascript code using Nashorn, specially the duplicated one that suggests 31piy in the first comment.

Then I assume that your real problem is to reach the javascript file that contains your code, present in your webapp folder. I can see some possible answers to that:

Here some fellows suggest possible ways to reach the file using Spring methods: Accessing files/directories in webapp folder in Spring You should consider if there is a way available to your particular framework

However: is there a good reason for that file to be in your webapp folder? Is its logic necessary at all in the client side? Since you need the logic in the server side, I would not (even for prudence) expose it to the client of your application. If it is not necessary in the client side, don't expose it. Just keep it, let's say, in your application's src/main/resources directory (assuming you build it with maven or gradle) and access it cleanly from your classloader:

// Access the resource from the classloader
try {
    reader = new InputStreamReader(
        YourServletOrWhateverClass.class.getClassLoader().
            getResourceAsStream("your_javascript_file.js"), 
                Charset.forName("UTF-8")); 
    ScriptEngineManager manager = new ScriptEngineManager();
    ScriptEngine engine = manager.getEngineByName("JavaScript");
    engine.eval(reader);            

    Invocable inv = (Invocable) engine;
    inv.invokeFunction("your_function");
}
catch(NoSuchMethodException nsme) {
    nsme.printStackTrace();
}
catch(ScriptException se) {
    se.printStackTrace();
}
finally {
    try {
        reader.close();
    }
    catch(IOException ioe) {
        ioe.printStackTrace();
    }
}

Thanks for suggesting workaround. Solved by loading context in java and using it to read js file and then invoke js methods. Keeping the logic at client side is required as I am using js libraries to export graphs and images in PDF. — shrutika ukey, Apr 12 '18 at 09:55

Call js methods from java

1 Answers1