jeudi 7 mars 2019

How to send information of a checkbox from the view to the controller in Thymeleaf?

I'm trying to send the values of looped checbox for print them in the controller. When I press a button, I want the information of the selected checbox to be send to the controller and print it in the console, but when I press my button to send the information to the controller method, it throws me a NullPointerException. My HTML look like this:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Select Cities</title>
    <link rel="stylesheet" type="text/css" href="../css/bootstrap.min.css">
</head>
<body>
<div class="container">
    <div class="row align-items-center">
        <div class="col-4 mt-3">
            <form action="">
                <div class="form-check"  th:each="names : ${namesOfCities}">
                    <label for="" class="form-check-label">
                        <input type="checkbox" name="lista" th:value="${names}" th:text="${names}">
                    </label>
                </div>
                <a href="#"th:href="@{/starbucks/showSelectedCities}" class="btn btn-primary">Aceptar</a>
            </form>
        </div>
        <div class="col-8">
            <div id="chart" style="height: 400px"></div>
        </div>
    </div>
</div>
<script src="https://code.highcharts.com/highcharts.js"></script>
<script src="https://code.highcharts.com/highcharts-3d.js"></script>
<script src="https://code.highcharts.com/modules/exporting.js"></script>
<script src="../js/jquery-3.3.1.min.js"></script>
<script src="../js/popper.min.js"></script>
<script src="../js/bootstrap.min.js"></script>
</body>
</html>

Here in the HTML I create a checkbox for each element in the list sended by the controller.

I have two methods in the Controller, the first one:

   @GetMapping("/selectCities")
    public ModelAndView selectCities(Model model){
        ModelAndView mav = new ModelAndView(ViewConstant.SELECT_CITIES);
        //List<String> citiesNames = namesOfCities();
        List<String> citiesNames = recortarList();
        model.addAttribute("namesOfCities", citiesNames);
        return mav;
    }

This method shows the HTML view and send a List of String that contains cities names.

The second method looks like this:

@GetMapping("/showSelectedCities")
    public ModelAndView showSelectedCities(@RequestParam(name = "lista", required = false)List<String> id){
        ModelAndView mav = new ModelAndView(ViewConstant.SELECT_CITIES);
        for(int x=0;x<id.size();x++){
            System.out.println(id.get(x));
        }
        return mav;
    }

In this I want to recive the names of the city sended by the view and print them in the console, but when I try it throws me a NullPointerException. How is the correct form to send information from a checkbox to the controller?




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