jqGrid shows no data from the restful services

My jqGrid function brings no data, which comes from Restful Web Services. First below url shows json data successfully in web browser.

http://localhost:8080/RESTfulTestWeb/rest/services/getJson/aupres

{"user":[
           {"id":"aupres","passwd":"aaa","age":45,"name":"father"},
           {"id":"hwa5383","passwd":"bbb","age":40,"name":"mother"},
           {"id":"julian","passwd":"ccc","age":15,"name":"son"}

]}

But my bugs-full jqGrid brings nothing. These are my codes

<!DOCTYPE html>
<html>
<head>
<meta charset="EUC-KR">
<title>jQuery Test</title>
<link rel="stylesheet" type="text/css" media="screen" href="jquery-ui.css"/>
<link rel="stylesheet" type="text/css" media="screen" href="ui.jqgrid.css"/>
<script type="text/javascript" src="jquery-2.2.0.min.js"></script>
<script type="text/javascript" src="jquery.jqGrid.min.js"></script>
</head>
<body>
<table id="grid"></table>
<div id="pager"></div>
<script type="text/javascript">
$(document).ready(function(){
    $("#cl").click(function(){

        $Grid = $("#grid");
        $Grid.jqGrid({
            mtype: "get",
            url: "http://localhost:8080/JQueryJsonWeb/rest/services/getJson/aupres",
            restful : true,
            contentType: "text/json; charset=utf-8",
            dataType: "json",
            jsonReader : {
                root : "user",
                id : "id"
            },
            colNames : [
                'id',
                'passwd',
                'age',
                'name'
            ],
            colModel : [
                { name : 'id',        width:40,  align:'center'},
                { name : 'passwd',    width:80,  align:'left'  },
                { name : 'age',       width:80,  align:'left'  },
                { name : 'name',      width:80,  align:'right' }
            ],
            pager : '#pager',
            rowNum : '10',
            multiselect : true,
            postData : {
                   id : 'id',
                   passwd : 'passwd',
                   age : 'age',
                   name : 'name'
              },
        });  
    })
});
</script>
<button id="cl">click</button>
</body>
</html>

Actually I have no idea how to contain the json response in Grid.jqGrid function. Where is json responses contained in Grid.jqGrid?