Java - Call javascript functions from java

Calling external javascript function.

Sample Program:

import java.io.IOException;

import java.nio.charset.StandardCharsets;

import java.nio.file.Files;

import java.nio.file.Paths;

import javax.script.Invocable;

import javax.script.ScriptEngine;

import javax.script.ScriptEngineManager;

import javax.script.ScriptException;

public class SampleJsTest {

public static void main(String[] args) throws NoSuchMethodException, ScriptException, IOException {

//create a script engine manager

   ScriptEngineManager manager = new ScriptEngineManager();

//create a JavaScript engine

ScriptEngine engine = manager.getEngineByName("JavaScript");

// read script file

engine.eval(Files.newBufferedReader(Paths.get(System.getProperty("user.dir")+"\\js\\myscripts.js"), StandardCharsets.UTF_8));

Invocable inv = (Invocable) engine;

//call function from script file

double result = (double) inv.invokeFunction("addNumbers", "10","4");

System.out.println(result);

String name = (String) inv.invokeFunction("greeting", "\"Praveen\"");

        System.out.println(name);

}

}

Note:

Adds two int's in javasript but returns double. 

Reference: http://stackoverflow.com/questions/15528573/rhino-js-scriptengine-from-java-integers-in-doubles-out

Writing javascript in the java code and calling javascript function

Sample Program:

import java.io.IOException;

import javax.script.Invocable;

import javax.script.ScriptEngine;

import javax.script.ScriptEngineManager;

import javax.script.ScriptException;

public class SampleJsTest {

public static void main(String[] args) throws NoSuchMethodException, ScriptException, IOException {

//create a script engine manager

ScriptEngineManager manager = new ScriptEngineManager();

//create a JavaScript engine

   ScriptEngine engine = manager.getEngineByName("JavaScript");

//Javascript inside java code

   //JavaScript code in a String

   String script1 = (String) "function add(a,b) {return (parseInt(a)+parseInt(b))}";

   engine.eval(script1);

  

   String script2 = (String) "function greeting(name) {return 'Welcome '+name}";

   engine.eval(script2);

   Invocable inv = (Invocable) engine;

   double result = (double) inv.invokeFunction("add", "1","4" );  

   System.out.println("Add : "+result);

   String name = (String) inv.invokeFunction("greeting", "Praveen Kumar");

   System.out.println("Name : "+name);

}

}