springmvc4 ajax回调data为[object object]

	@ResponseBody 
	public Map<String, Object> testJson(
			@RequestParam("name") String name,@RequestParam("city") String city) {
		Map<String, Object> map = new HashMap<>();
		System.out.println(name + city);
		map.put("aa", "aa");
		map.put("bb", "bb");
		map.put("cc", "cc");
		return map;
	}

$.post("${APP_PATH}/test/testjson", {
					name : "Donald Duck",
					city : "Duckburg"
				}, function(data, status) {
					var jdata = JSON.stringify(data);
					alert("Data: " + data + "\nStatus: " + status);
					$("#json").text(data.aa);
				});

前后端代码如上。

返回结果alert显示data：[object object]

我将springmvc配置<value>application/text;charset=UTF-8</value>可以data.aa取出对象

配置为：                 <value>application/json;charset=UTF-8</value>不能直接取data.aa