I am trying to save checkbox values in localstorage using map. so that i can filter result using map. I am able to store map key-values in localstorage using javascript. but later when i retreive and pass map from localstorage to controller, I am getting map with null values.

this is my code

store map in localstorage

$(':checkbox[name=brand]').on('change', function() {
    var assignedTo = $(':checkbox[name=brand]:checked').map(function() {
        return this.id;
    }).get();
    localStorage.setItem('brands', JSON.stringify(assignedTo))
});

localstorage

passing to controller

$.ajax({
    type : "POST",
    url : "filter",
    data : {
        txtMaxAge : localStorage.getItem('txtMaxAge'),
        brands : JSON.parse(localStorage.getItem("brands"))

    }, // parameters
    success : function(result) {
        // alert('changed');
        }
});

controller

@RequestMapping("/filter")
@ResponseBody
public String filter(
        @RequestParam(value = "txtMaxAge", required = false) String txtMaxAge,
        @RequestParam(value = "brands", required = false) Map<String, String> brands,
        HttpServletRequest request, HttpServletResponse response) {

    System.out.println("max"+txtMaxAge);

    System.out.println("printing map----");

         for (Map.Entry<String,String> entry : brands.entrySet())  
            System.out.println("Key = " + entry.getKey() + 
                             ", Value = " + entry.getValue()); 
    return "send data";
}

I am getting this error

max10000000
printing map----
2018-12-15 13:37:59.142  WARN 13672 --- [nio-8080-exec-1] .m.m.a.ExceptionHandlerExceptionResolver :
Resolved [java.lang.NullPointerException] to ModelAndView: reference to view with name 'error';
model is {errorTitle=Contact Your Administrator!!, errorDescription=java.lang.NullPointerException

What i am doing wrong here?

I am trying to save checkbox values in localstorage using map. so that i can filter result using map. I am able to store map key-values in localstorage using javascript. but later when i retreive and pass map from localstorage to controller, I am getting map with null values.

this is my code

store map in localstorage

$(':checkbox[name=brand]').on('change', function() {
    var assignedTo = $(':checkbox[name=brand]:checked').map(function() {
        return this.id;
    }).get();
    localStorage.setItem('brands', JSON.stringify(assignedTo))
});

localstorage

passing to controller

$.ajax({
    type : "POST",
    url : "filter",
    data : {
        txtMaxAge : localStorage.getItem('txtMaxAge'),
        brands : JSON.parse(localStorage.getItem("brands"))

    }, // parameters
    success : function(result) {
        // alert('changed');
        }
});

controller

@RequestMapping("/filter")
@ResponseBody
public String filter(
        @RequestParam(value = "txtMaxAge", required = false) String txtMaxAge,
        @RequestParam(value = "brands", required = false) Map<String, String> brands,
        HttpServletRequest request, HttpServletResponse response) {

    System.out.println("max"+txtMaxAge);

    System.out.println("printing map----");

         for (Map.Entry<String,String> entry : brands.entrySet())  
            System.out.println("Key = " + entry.getKey() + 
                             ", Value = " + entry.getValue()); 
    return "send data";
}

I am getting this error

max10000000
printing map----
2018-12-15 13:37:59.142  WARN 13672 --- [nio-8080-exec-1] .m.m.a.ExceptionHandlerExceptionResolver :
Resolved [java.lang.NullPointerException] to ModelAndView: reference to view with name 'error';
model is {errorTitle=Contact Your Administrator!!, errorDescription=java.lang.NullPointerException

What i am doing wrong here?

• javascript
• java
• spring
• spring-boot

• Change @RequestParam(value = "brands", required = false) Map<String, String> brands,to @RequestParam(value = "brands", required = false) ArrayList<String> brands, – Shubham Dixit Commented Dec 15, 2018 at 9:13
• @Jai Dixit value = "brands" will give us a null in brands if brands : ['aaa','bbb'] in JS. – Anatoly Samoylenko Commented Dec 15, 2018 at 9:24
• @Jai Dixit @RequestParam(value = "brands", required = false) ArrayList<String> brands dosent work giving same error. – vidy Commented Dec 15, 2018 at 11:54
• @vidy JSON.parse(localStorage.getItem("brands")) remove this donot parse send the stringified response and use this @RequestParam(value = "brands", required = false) List<String> brands – Shubham Dixit Commented Dec 15, 2018 at 12:47
• @Jai Dixit giving same error. – vidy Commented Dec 15, 2018 at 12:56

3 Answers 3

The problem is that brands is not map type,it is an array of strings. Change the type accordingly and it should work.

Try to change your controller code:

@RequestMapping(value = "/filter")
@ResponseBody
public String filter(
        @RequestParam(value = "txtMaxAge", required = false) String txtMaxAge,
        @RequestParam(value = "brands[]", required = false) String[] brands,
        HttpServletRequest request, HttpServletResponse response) {

    System.out.println("max " + txtMaxAge);
    System.out.println("map " + brands);

    return "send data";
}

if you really want brands in a Map ; here's my take on it.

Here my controller

@RequestMapping(value = "/filter", method = RequestMethod.POST)
    public String submission(@RequestParam("brands")String brands) {

        try {

            JSONParser parser = new JSONParser();
            JSONObject ob = (JSONObject)parser.parse(brands);

            Map<String,String> mp = new HashMap<>();
            mp.put(ob.keySet().toString(), ob.values().toString());

            for(Map.Entry<String,String> entry : mp.entrySet()) {

                System.out.println("Key = " + entry.getKey() + 
                        ", Value = " + entry.getValue().toString()); 
            }

        } catch (ParseException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }


        return "home";
    }

Here's my ajax call,

$.ajax({
  type: "POST",
  url: "${pageContext.request.contextPath}/Submit",
  data: {

      brands: localStorage.getItem("brands")
  },
  success : function() {
       console.log('done');
  }

});