Redirect stdout of KotlinScriptEngine in javax.script API

Question

I am executing kotlin scripts using javax.script API. I want to capture the output and print the logs later.

I am able to do this for nashorn script engine , but the same does not work on KotlinScriptEngine.

    public void testExampleNashorn() throws ScriptException {
        ScriptEngine engine = new ScriptEngineManager().getEngineByName("nashorn");
        ScriptContext context = engine.getContext();
        StringWriter writer = new StringWriter();
        context.setWriter(writer);

        engine.eval("print(\"Welocme to java worldddd\")");

        String output = writer.toString();

        System.out.println("Script output: " + output);
    }

Output for Nashorn

Script output: Welocme to java worldddd

The same code snippet when adjusted for kotlin as below

    public void testExampleKotlin() throws ScriptException {
        ScriptEngine engine = new ScriptEngineManager().getEngineByName("kotlin");
        ScriptContext context = engine.getContext();
        StringWriter writer = new StringWriter();
        context.setWriter(writer);

        engine.eval("println(\"Welocme to java worldddd\")");

        String output = writer.toString();

        System.out.println("Script output: " + output);
    }

Output for kotlin

Welocme to java worldddd
Script output: 
null

I am using kotlin version 1.3.72 Any help is highly appreciated. Thanks.

score 1 · Accepted Answer · answered Jun 05 '20 at 11:37

This is how I managed to capture logs of KotlinScriptEngine execution.

public Object captureOut(String script,Bindings bindings)  {
        Object result=null;
        ByteArrayOutputStream os = new ByteArrayOutputStream();
        PrintStream ps = new PrintStream(os);
        PrintStream console = System.out;
        System.setOut(ps);

        try {
            result = kotlinScriptingEngine.eval(script,bindings);
        } catch (ScriptException scriptException) {
            scriptException.printStackTrace(ps);
        }  finally {
            System.out.flush();
            System.setOut(console);
        }
        System.out.println("Kotlin Script Output: " + os.toString());
        return result;
}

Redirect stdout of KotlinScriptEngine in javax.script API

1 Answers1