Call a Java method from Javascript

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[edit] Implementations

[edit] Java

You call a Java method by giving its fully qualified name. In the following snippet, the first example calls the method in the Toolkit to retrieve the screen resolution. The second example, calls a method in our Applet. NOTE: On IE4 or better, you can't call java.* methods directly from Javascript or Jscript. IE javascript can only access the public methods of an applet (a class derived from java.applet.Applet) but don't have a general access to other java classes . So the solution is simple, wrap the java.* call in a public method of a "dummy" Applet.

[Java applet]


import java.awt.*;
import java.applet.*;
public class InJava extends Applet{
        public void sayHello() {
                Graphics g = getGraphics();
                g.drawString("Hello from JAVA!", 10, 10);
        }
}

[Javascript and HTML (Netscape)]


<HTML><HEAD></HEAD><BODY>
<SCRIPT>
function getScreenDimension() {

        alert("Screen Dimension\n" +
        "  width:" +
        java.awt.Toolkit.getDefaultToolkit().getScreenSize().width +
        " height:" +
        java.awt.Toolkit.getDefaultToolkit().getScreenSize().height);
}
</SCRIPT>
<FORM>
<INPUT type="button" value="call Java Applet method"
onClick = "document.myApplet.sayHello()">
</FORM>

<INPUT type="button" value="call Java method direct"
onClick = "getScreenDimension()">

<APPLET CODE="InJava.class"
NAME="myApplet"
HEIGHT=100 WIDTH=100>
</APPLET>
</BODY></HTML>

Try it here


import java.awt.*;
import java.applet.*;
// (IE and Netscape ok)
public class InJava2 extends Applet{
        public int getScreenWidth() {
                return Toolkit.getDefaultToolkit().getScreenSize().width;
        }
        public int getScreenHeight() {
                return Toolkit.getDefaultToolkit().getScreenSize().height;
        }
}

[Javascript and HTML (IE and Netscape)]


<HTML><HEAD></HEAD><BODY>
<SCRIPT>
function getScreenDimension() {
        alert("Screen Dimension\r\n  width:" +
        document.myApplet.getScreenWidth() +
        " height:" +
        document.myApplet.getScreenHeight() );
}
</SCRIPT>
<FORM>
<INPUT type="button" value="call JAVA"
onClick = "getScreenDimension()">
</FORM>
<APPLET CODE="InJava2.class"
NAME="myApplet"
HEIGHT=100 WIDTH=100>
</APPLET>
</BODY></HTML>

Try it here

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Category: Java