How to show error message on same page in spring MVC

Question

I am calling a controller in spring mvc with form data.

Before saving, I check if the id is a certain range. If the id is not within the range, I need to show a message on the same page saying The id selected is out of Range, please select another id within range.

I found samples on internet where I can redirect to failure jsp in case anything goes wrong. But how to do it in my case?

@RequestMapping(value = "/sendMessage")
public String sendMessage(@ModelAttribute("message") Message message,
        final HttpServletRequest request) { 
    boolean check = userLoginService.checkForRange(message.getUserLogin());
    if(!check){
        return "";  //What Should I do here??????
    }
}

Answer 1

A simple approach would be to add your error message as a model attribute.

@RequestMapping(value = "/sendMessage")
public String sendMessage(@ModelAttribute("message") Message message,
        final HttpServletRequest request, Model model) {

    boolean check = userLoginService.checkForRange(message.getUserLogin());
    if(!check){
        model.addAttribute("error", "The id selected is out of Range, please select another id within range");
        return "yourFormViewName";
    }
}

Then your jsp can display the "error" attribute if it exists.

<c:if test="${not empty error}">
   Error: ${error}
</c:if>

Edit

Here's a rough, untested implementation of validation over ajax. JQuery assumed.

Add a request mapping for the ajax to hit:

@RequestMapping("/validate")
@ResponseBody
public String validateRange(@RequestParam("id") String id) {

    boolean check = //[validate the id];
    if(!check){
        return "The id selected is out of Range, please select another id within range";
    }
}

Intercept the form submission on the client side and validate:

$(".myForm").submit(function(event) {

    var success = true;

    $.ajax({
        url: "/validate",
        type: "GET",
        async: false, //block until we get a response
        data: { id : $("#idInput").val() },
        success: function(error) {
            if (error) {
                $("#errorContainer").html(error);
                success = false;
            }
        }
    });

    return success;

});