Error when using javax.script package

Question

Hi
I want to call a javascript method from a .js file from .java class.
when i searched, i came to understand that using jdk1.6 i can use javax.script package tht provide me what i needed.
using the reply i got from i earlier post, i tried one example.
public void show() {
ScriptEngineManager engineMgr = new ScriptEngineManager();
ScriptEngine engine= engineMgr.getEngineByName("JavaScript");
try {
engine.eval(new FileReader("D:/ShowScript.js"));
Invocable invocableEngine = (Invocable) engine;
//show_message is my function in ShowScript.js file
invocableEngine.invokeFunction("show_message",null);
} catch (Exception e) {
e.printStackTrace();
ShowScript.js
function show_message()
println("===> hi");
alert("hi");
When i execute my program, im getting the following error
javax.script.ScriptException: sun.org.mozilla.javascript.internal.EcmaError: ReferenceError: "alert" is not defined. ( #8) in at line number 8
at com.sun.script.javascript.RhinoScriptEngine.invoke(RhinoScriptEngine.java:184)
at com.sun.script.javascript.RhinoScriptEngine.invokeFunction(RhinoScriptEngine.java:142)
at testbuiltin.backing.Show_alert.show(Show_alert.java:81)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at com.sun.el.parser.AstValue.invoke(AstValue.java:151)
at com.sun.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:283)
When i remove the alert() from the js file, the println is working. But what i neede is the alert.
Can anyone plz help me to solve this problem.

Answer 1

As you're talking about "backing beans", are you using JSF?
After all, this is definitely not the way to let Java and JS interact with each other. Java runs at the server side. JS runs at the client side. Java can write JS code to the response, but definitely cannot call it. JS can access the HTML DOM and invoke requests to the server (form.submit() and AJAX and so on) and send parameters along the request, but definitely cannot call Java classes and methods independently. Nothing more and nothing less than that.