lugar - Llama a funciones javascript externas desde código java.

javascript caracteristicas

Question

Al usar Java Scripting API, puedo ejecutar JavaScript dentro de Java. Sin embargo, ¿puede alguien explicar qué necesitaría agregar a este código para poder llamar a las funciones que están en 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 = (String)"function hello(name) {print (''Hello, '' + name);}";
String script2 = (String)"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.
}
}

Answer 1

Digamos que su archivo jsfunctions.js tiene una función "mostrar" y este archivo se almacena en C: /Scripts/Jsfunctions.js

jsfunctions.js

var display = function(name) {
print("Hello, I am a Javascript display function",name);
return "display function return"
}

Ahora, en tu código java, te recomendaría que uses Java8 Nashorn. En tu clase de java,

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();
}
}
}

Nota: Obtenga la ruta de acceso absoluta de su archivo javascript y reemplácelo en FileReader () y ejecute el código java. Deberia de funcionar.

Answer 2

Use ScriptEngine.eval(java.io.Reader) para leer el 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");

Answer 3

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);
}