JavaScript实现异步调用例子

======================

js部分：

var url = "<%=request.getContextPath()%>/servlet/AjaxCheckCallListServlet?assignCallIdList="+assignCallIdStr;
	var checkResult = "";
	$.ajax({
		async : false,  //false表示同步，true表示异步
		type : "post",
		url : url,
		success : function(result) {
			checkResult = result;  //result是返回数据
		}
	});
	if (checkResult != "") {
		alert(checkResult + " not belong to the current UM. ");
		return false;
	}

servlet部分：

public class AjaxCheckCallListServlet extends DBServlet {
	private static final long serialVersionUID = 1L;
	private HttpServletRequest request;
	private HttpServletResponse response;

	protected String perform(HttpServletRequest request,
			HttpServletResponse response, StrutsMessage message)
			throws ServletException, IOException, SQLException, DataException,
			Exception {
		this.response = response;
		this.request = request;
		
		User user = (User)request.getSession().getAttribute("user");
		String userId = user.getUser_id();

		String assignCallIdList = Utilities.replaceNullWithBlank(request.getParameter("assignCallIdList"));
		CallListDao callListDao = new CallListDao();
		String ret = callListDao.checkCallList(assignCallIdList, userId);
		if(!ret.isEmpty()){
			ret = ret.substring(0, ret.length()-1);
		}
		response.getWriter().print(ret);  //将结果写到response里
		return null;
	}
}