Spring-de json list nasıl göndere bilirim?

Merhaba.secilmis checkboxların id-lerini arraye doldurup servere göndermek istiyorum.Amma bir türlü yapamadım :(

Benim Java kodum:

 @Autowired
 ParamService paramService;

 @RequestMapping(value = "/refresh", method = RequestMethod.POST, produces = "application/json", consumes = "application/json")
 public @ResponseBody String refreshModelParamRel(@RequestBody ParamWrapper pw) {
       System.out.println("params size"+pw.getParams().size());
 }

ParamWrapper:

 public class ParamWrapper {

    private List<ParamDTO> params;
    private Integer modelId;

    public ParamWrapper() {
    }

    public List<ParamDTO> getParams() {
         return params;
    }

    public void setParams(List<ParamDTO> params) {
        this.params = params;
    }

    public Integer getModelId() {
        return modelId;
    }

    public void setModelId(Integer modelId) {
        this.modelId = modelId;
    }    
}

Bu da json:

    function addModelParams() {

        var paramWrapper = {};

        paramWrapper["modelId"] = selectedModelId;

        var params = {};
        var allParams = $("input[name='param']");
        for (i = 0; i < allParams.length; i++) {
            var param = {};
            param["id"] = allParams[i].value;
            param["checked"] = allParams[i].checked;
            params[i] = param;
        }

        paramWrapper["params"] = params;

        var xhr = new XMLHttpRequest();
        xhr.onreadystatechange = function ()
        {
            if (xhr.readyState == 4 && xhr.status == 200)
            { 
                alert(xhr.responseText);
            }
        }

        xhr.open("POST", "http://localhost:8080/ButelefonAPI/modelparams/refresh", true);
        xhr.setRequestHeader('Content-Type', 'application/json'); 
        xhr.send(JSON.stringify(paramWrapper));
    }