struts2 json传递对象

今天在用struts2 异步请求从后台传一个对象到前台时遇到了一个小小的问题，现在此作一个标记，把主要的代码贴上以作备忘。

struts.xml

<action name="getSystemContactorInfo" class="userAction" method="getSystemContactorInfo">
			<result type="json">
				<param name="includeProperties">systemContactor\.userName,systemContactor\.cellPhone,
					systemContactor\.notesMail
				</param>
				<!-- <param name="includeProperties">systemContactor</param> 这样不对-->
				<!-- <param name="includeProperties">systemContactor.*</param> 这样同样不正确-->
			</result>
		</action>

UserAction

public String getSystemContactorInfo() {
		UserModel systemContactor = new UserModel();
		systemContactor.setUserName("张三");
		systemContactor.setCellPhone("13240151465");
		systemContactor.setNotesMail("[e-mail]");
		return Action.SUCCESS;
	 }

UserModel

public class UserModel{
   private String userName;
   private String cellPhone;
   private String notesMail;
//省略get、set方法
}

jsp页面中

$.ajax({
			type:'post',
			url: 'getSystemContactorInfo.action',
			dataType: 'json',
			async: true,
			success: function showContent(json) {
				var userInfo = json.systemContactor;
				$("#userName").html(userInfo.userName);
				$("#cellPhone").html(userInfo.cellPhone);
				$("#notesMail").html(userInfo.notesMail);
			}
		});

<param name="includeProperties">systemContactor</param> 当systemContactor为一个字串或数字时可以这样写
<param name="includeProperties">systemContactor.*</param>当systemContactor为list时可这样传
到现在也不是太明白当systemContactor为一个对象时为什么不能直接写在里面，在此标记一下。嗯，有必要去看下官方的api了