How to call a method javaservlet in function javascript?

Question

function ShowMessage() {
    var url = '/primes/PrimesServlet';
    var result = CQ.HTTP.eval(url);
    var i = Number(document.getElementById("input").value);
    var str = document.getElementById("test");
    // if(result.checkPrimes(i)) // Want to call here
    str.innerHTML = i + " là số nguyên tố";
    // else str.innerHTML = i + " là hợp số";
    document.getElementById("output").style.display="block";
}

public class PrimesServlet extends HttpServlet {
    public boolean checkPrimes(long n) {
        boolean _return;
        MillerRabin obj = new MillerRabin();
        _return = obj.checkPrimes(n);
        return _return;
    }
 }

I want to call the method checkPrimes(long n) from my function ShowMessage(), but I can't.

You may want to read up on en.wikipedia.org/wiki/Ajax_(programming) — aquaraga
– aquaraga, Commented Oct 28, 2013 at 10:34
You'll need to call it via an AJAX request, since your java code is running on your server, and your JavaScript is executed client-side. Expose the Java method as a web service, make an XMLHttpRequest from your JS, and make the return type of your Java method something which you can serialize, and parse on the front-end. — nbrooks
– nbrooks, Commented Oct 28, 2013 at 10:35

Donald Duck is with Ukraine · Accepted Answer · 2017-06-18 13:02:08Z

2

I want to call method checkPrimes(long n) from function javascript "ShowMessage()" but I can't.

Yes you cannot.

Java plays on server side and javascript plays on client side.

Java needs compiled code and Javascript is just a scripting language interpreted by the browser.

What you need is just make a request to server.

That request may be

form submission
Ajax

Besides all with javascript you can check Prime like.

function isPrime1(n) {
    if (isNaN(n) || !isFinite(n) || n%1 || n<2) return false; 
    var m=Math.sqrt(n);
    for (var i=2;i<=m;i++) if (n%i==0) return false;
    return true;
}

Just found here.

If you want to make a request with JavaScript, Ajax is your friend.

A great example :How to use Servlets and Ajax?

edited Jun 18, 2017 at 13:02

Donald Duck is with Ukraine

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answered Oct 28, 2013 at 10:33

Suresh Atta

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2 Comments

anhhtbk Over a year ago

I don't need that.CheckPrime only is exampe. I want to use sevlet in javascript.

Suresh Atta Over a year ago

So Ajax is your friend.See here.stackoverflow.com/questions/4112686/…

SpringLearner · Accepted Answer · 2013-10-28 10:34:48Z

0

you can not call methods using javascript because javascript runs in client side and javacodes lies in server side.

to call a method checkPrimes you can use ajax.

answered Oct 28, 2013 at 10:34

SpringLearner

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Comments

Philipp Sander · Accepted Answer · 2013-10-28 10:35:12Z

0

You could ether use AJAX-Calls or write a controller and call it via a request from the JavaScript.

The proble is (as the others said), that javascript runs in the browser of the client and your businesslogic runs on the webserver.

With AJAX you can trigger the server to execute code.

answered Oct 28, 2013 at 10:35

Philipp Sander

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Comments

Masudul · Accepted Answer · 2013-10-28 10:44:05Z

0

You can't call like that. You should do operation on doGet or doPost methods than write the result on PrintWriter.write method.

public class PrimesServlet extends HttpServlet {

 protected void doGet(HttpServletRequest req, HttpServletResponse resp)
                           throws ServletException, IOException{
 boolean _return;
 MillerRabin obj = new MillerRabin();
 _return = obj.checkPrimes(n);
 resp.getWriter().write(_return);

 }
}

answered Oct 28, 2013 at 10:44

Masudul

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1 Comment

anhhtbk Over a year ago

If I use "resp.getWriter().write(_return);", browser will open new website. I want to keep my old website. p.s: My English is bad.

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