How to Execute Javascript Function in Java

Execute Javascript Function in Java>

In this example, We will show you simple program about, How to Execute Javascript function in Java. The example program has been tested and shared in the same post.

Example Program

package com.dineshkrish;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import javax.script.Invocable;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;
/**
* 
* @author Dinesh Krishnan
*
*/
public class JavaScriptRunner {
public static void main(String[] args) {
// script engine
final String ENGINE_NAME = "nashorn";
// defining Script Engine Manager object
ScriptEngineManager manager = new ScriptEngineManager();
// defining the Script Engine
ScriptEngine engine = manager.getEngineByName(ENGINE_NAME);
try {
// file name or complete file name with path
final String fileName = "script.js";
// creating the file object by passing the file name as argument
File file = new File(fileName);
// creating the file reader object by passing file object as argument
FileReader fileReader = new FileReader(file);
// loading the reader object to engine
engine.eval(fileReader);
// creating invocable object
Invocable invocable = (Invocable)engine;
// invoking the function 'sayHello('Dinesh Krishnan')'
String message = (String)invocable.invokeFunction("sayHello", "Dinesh Krishnan");
// printing the result
System.out.println(message);
// invoking the function 'sayBye('Dinesh Krishnan')'
message = (String)invocable.invokeFunction("sayBye", "Dinesh Krishnan");
// printing the result
System.out.println(message);
} catch (ScriptException e) {
System.out.println(e.getMessage());
e.printStackTrace();
} catch (FileNotFoundException e) {
System.out.println(e.getMessage());
e.printStackTrace();
} catch (NoSuchMethodException e) {
System.out.println(e.getMessage());
e.printStackTrace();
}
}
}

Sample Script (script.js)

var sayHello = function(name) {
return "Hello, "+name;
};
var sayBye = function(name) {
return "Bye, "+name;
};

Output

Hello, Dinesh Krishnan
Bye, Dinesh Krishnan

References

1. JavaDoc – ScriptEngineManager Class
2. JavaDoc – ScriptEngine Interface
3. JavaDoc – File Class
4. JavaDoc – FileReader Class
5. JavaDoc – Invocable Interface
6. JavaDoc – invokeFunction() method

Dinesh Krishnan

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