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Asked: 2026-06-01T17:40:21+00:00

I have helloJava.HTML in my GWT project , within that html file , i

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I have helloJava.HTML in my GWT project , within that html file , i have this javascript code

                        <script type="text/javascript">
function testJavaScript(var input){
    var var1inJS = "Default value";

    alert("Value of Var1 = " + var1inJS);
    var1inJS = input;
    alert("Value of Var1 = " + var1inJS);

    var var2inJS = "Waht is the value of Var2";

    alert("Value of Var2 = " + var2inJS);

}

now i want to call this method from my onmoduleLoad class(i.e from my java class).

is it possible ?

hellojava.html file 

                            <!doctype html>
<!-- The DOCTYPE declaration above will set the     -->
<!-- browser's rendering engine into                -->
<!-- "Standards Mode". Replacing this declaration   -->
<!-- with a "Quirks Mode" doctype is not supported. -->

<html>
  <head>
    <meta http-equiv="content-type" content="text/html; charset=UTF-8">

    <!--                                                               -->
    <!-- Consider inlining CSS to reduce the number of requested files -->
    <!--                                                               -->
    <link type="text/css" rel="stylesheet" href="HelloJSNI.css">

    <!--                                           -->
    <!-- Any title is fine                         -->
    <!--                                           -->
    <title>Web Application Starter Project</title>

    <!--                                           -->
    <!-- This script loads your compiled module.   -->
    <!-- If you add any GWT meta tags, they must   -->
    <!-- be added before this line.                -->
    <!--                                           -->
    <script type="text/javascript" language="javascript" src="hellojsni/hellojsni.nocache.js"></script>

    <script type="text/javascript">
    function testJavascript(var input){
        window.jsniAlert();
        var var1inJS = "Default value";

        alert("Value of Var1 = " + var1inJS);
        var1inJS = input;
        alert("Value of Var1 = " + var1inJS);

        var var2inJS = "Waht is the value of Var2";

        alert("Value of Var2 = " + var2inJS);

    }

    function callJava(){

    }
    </script>
  </head>

  <!--                                           -->
  <!-- The body can have arbitrary html, or      -->
  <!-- you can leave the body empty if you want  -->
  <!-- to create a completely dynamic UI.        -->
  <!--                                           -->
  <body>

    <!-- OPTIONAL: include this if you want history support -->
    <iframe src="javascript:''" id="__gwt_historyFrame" tabIndex='-1' style="position:absolute;width:0;height:0;border:0"></iframe>

    <!-- RECOMMENDED if your web app will not function without JavaScript enabled -->
    <noscript>
      <div style="width: 22em; position: absolute; left: 50%; margin-left: -11em; color: red; background-color: white; border: 1px solid red; padding: 4px; font-family: sans-serif">
        Your web browser must have JavaScript enabled
        in order for this application to display correctly.
      </div>
    </noscript>

    <h1>JSNI EXAMPLE</h1>

    <table align="center">
      <tr>
        <td colspan="2" style="font-weight:bold;"></td>        
      </tr>
      <tr>
        <td id="nameFieldContainer"></td>
        <td id="sendButtonContainer"></td>
      </tr>
      <tr>
        <td colspan="2" style="color:red;" id="errorLabelContainer"></td>
      </tr>
    </table>
  </body>
</html>
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1 Answer

  1. Editorial Team

    The function syntax from Travis is correct, the problem is the name of the calling function and JS script is not right.

    Here are the corrections

    1. Error in the function declaration, you should not use var for
      the argument.

    2. Remove the first row window.jsniAlert();

    3. Correct the declaration of the second function function
      callJava(){       to function callJava(){

    Here is the code (lets call the function in JS testJSnative): 

    <script type="text/javascript">
function testJSnative(input){
    //window.jsniAlert();
    var var1inJS = "Default value";

    alert("Value of Var1 = " + var1inJS);
    var1inJS = input;
    alert("Value of Var1 = " + var1inJS);

    var var2inJS = "What is the value of Var2";

    alert("Value of Var2 = " + var2inJS);

}

function callJava(){

}
</script>

    Example of class implementing EntryPoint: 

      public void onModuleLoad() {

    Button jsniButton = new Button("call JS");
    jsniButton.addClickHandler(new ClickHandler() {

      @Override
      public void onClick(ClickEvent event) {

        callJavascript();
      }
    });
    RootPanel.get().add(jsniButton);
  } 

  public native void callJavascript() /*-{
    $wnd.testJSnative("hello");
  }-*/;

    I hope this will be helpful.

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