Question

I try to validate a field with ajax and a function which verify that the value is not already in base.

All examples I found are with php ; how to do with java ?

JSP code :

<form id="FLoginNew" action="Loginnew" method="post">
.....
<script>
$(document).ready(function(e) {
    $("#FLoginNew").validationEngine('attach', {promptPosition : "centerRight", scroll: false, validationEventTrigger: "blur", autoHidePrompt:true, autoHideDelay:3000 });
});
</script>

jquery.ValidationEngine-fr.js altered :

"ajaxLoginCall": {
                "url": "myapp.selvlets.DoublonLoginServlet",
                "extraDataDynamic": ['#login'],
                "alertText": "* Ce login est déjà pris",
                "alertTextOk": "* Ce login est disponible",
                "alertTextLoad": "* Chargement, veuillez attendre"
            },

As URL, I tried : "url": "/DoublonLogin", which is the declaration of the servlet mapping in web.xml.

Answer 1

I’m answering myself : I found the solution :

At first, the input class (I didn’t display) : class="validate[required,ajax[Ajaxdoublonlogin]]"

Then, the url of the Ajax call called “Ajaxdoublonlogin” : "Doublonlogin" as it is declared in the web.xml file. It’s a servlet.

The servlet :

• It must import a JSON librairy. I chose “JSONSimple” : simple and
  enough for what I want to do.
• Create a JSON array and put then name of the input field then true or false
  after verification is made.
• Create a writer in the response object and write the JSON array.

Nothing difficult ! ^_^

Example : “login” is the id of the input field

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    String login = new String(request.getParameter("login")); // we catch the value

    JSONArray jsres = new JSONArray(); // new JSON array

    jsres.add("login"); // 1st field : the field name = "login"

    if(<login in the database ?>) jsres.add(new Boolean(false)); // In database ? => false in the JSON array
    else jsres.add(new Boolean(true)); // Not in database > true in the JSON array !! 

    response.setContentType("application/json"); // The answer is in JSON content type
    response.setCharacterEncoding("UTF-8"); // Put the right encoding
    PrintWriter writer = response.getWriter();  // new answer writer

    try {
        writer.println(jsres); // WRITE !! ^_^
        log.info("Retour JSON : " + jsres);
        } catch(Exception e){
        log.error("Erreur lors du transfert JSON : " + e.getMessage());
    } finally {
        writer.close(); // Don't forget to close the writer
    }
}

It works fine…
If you have suggestions, I’ll take with pleasure !

Now, I’ll try to prevent the form submit because if the last condition is this condition, the submit appends ; I don’t know why…