How to pass JavaScript variables as parameters to JSF action method?

Question

I'm preparing some variables in JavaScript (in my specific case, I'd like to get GPS location):

function getVars() {
    // ...
    var x = locationInfo.lng; 
    var y = locationInfo.lat;
}

I'd like to send them to my managed bean via the below command button:

<h:commandButton value="submit" onclick="getVars()" action="#{bean.submit(x,y)}" />

public void submit(int x, int y) {
    // ...
}

How can I send x and y variables from JavaScript to JSF managed bean action method?

Answer 1

Let JS set them as hidden input values in the same form.

<h:form id="formId">
    <h:inputHidden id="x" value="#{bean.x}" />
    <h:inputHidden id="y" value="#{bean.y}" />
    <h:commandButton value="submit" onclick="getVars()" action="#{bean.submit}" />
</h:form>

function getVars() {
    // ...
    var x = locationInfo.lng; 
    var y = locationInfo.lat;

    document.getElementById("formId:x").value = x;
    document.getElementById("formId:y").value = y;
}

The command button action method could just access them as bean properties the usual way.

private int x;
private int y;

public void submit() {
    System.out.println("x: " + x);
    System.out.println("y: " + y);
    // ...
}

// Getters+setters.

An alternative is to use OmniFaces <o:commandScript> or PrimeFaces <p:remoteCommand> instead of <h:commandButton>. See also a.o. How to invoke a JSF managed bean on a HTML DOM event using native JavaScript?