Call external javascript functions from java code

Question

By using Java Scripting API  I am able to execute JavaScript within Java  However  can someone please explain what I would need to add to this code in order to be able to call on functions that are in C  Scripts Jsfunctions js  import javax script     public class InvokeScriptFunction   public static void main String   args  throws Exception       ScriptEngineManager manager   new ScriptEngineManager        ScriptEngine engine   manager getEngineByName  JavaScript            JavaScript code in a String     String script1    function hello name   print   Hello      name          String script2    function getValue a b    if  a     Number    return 1                        else return b            evaluate script     engine eval script1       engine eval script2        Invocable inv    Invocable  engine       inv invokeFunction  hello    Scripting         This one works

User · Accepted Answer

Use ScriptEngine eval java io Reader  to read the script  ScriptEngineManager manager   new ScriptEngineManager    ScriptEngine engine   manager getEngineByName  JavaScript       read script file engine eval Files newBufferedReader Paths get  C  Scripts Jsfunctions js    StandardCharsets UTF 8     Invocable inv    Invocable  engine     call function from script file inv invokeFunction  yourFunction    param

User · Answer

try           ScriptEngineManager manager   new ScriptEngineManager            ScriptEngine engine   manager getEngineByName  JavaScript            System out println  okay1            FileInputStream fileInputStream   new FileInputStream  C  Users Kushan eclipse-workspace sureson lk src main webapp js back end response js            System out println  okay2            if  fileInputStream    null            BufferedReader reader   new BufferedReader new InputStreamReader fileInputStream             engine eval reader            System out println  okay3               Invocable javascriptEngine   null           System out println  okay4            Invocable invocableEngine    Invocable engine           System out println  okay5             int x 0           System out println  invocableEngine is     invocableEngine            Object object   invocableEngine invokeFunction  backend message  x             System out println  okay6                       catch Exception e                System out println  erroe when calling js function   e

User · Answer

Let us say your jsfunctions js file has a function  display  and this file is stored in C  Scripts Jsfunctions js  jsfunctions js  var display   function name    print  Hello  I am a Javascript display function  name   return  display function return      Now  in your java code  I would recommend you to use Java8 Nashorn  In your java class   import java io FileNotFoundException  import java io FileReader   import javax script Invocable  import javax script ScriptEngine  import javax script ScriptEngineManager  import javax script ScriptException   class Test   public void runDisplay     ScriptEngine engine   new ScriptEngineManager   getEngineByName  nashorn    try     engine eval new FileReader  C  Scripts Jsfunctions js       Invocable invocable    Invocable  engine    Object result    result   invocable invokeFunction  display   helloWorld     System out println result     System out println result getClass         catch  FileNotFoundException   NoSuchMethodException   ScriptException e        e printStackTrace                  Note  Get the absolute path of your javascript file and replace in FileReader   and run the java code  It should work

[java] Call external javascript functions from java code

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