$("#ddd").click(function(){
	$.ajax({
		type:'post',
		url:"<%=basePath%>messageServlet?method=jsonTest",
		data:{id:2},
		success:function(data){
			alert(data);					
		},
		error : function() {
	  // view("异常！");
	  alert("异常！");
	 }
	});
});  

public void jsonTest(HttpServletRequest req, HttpServletResponse resp) {
		resp.setContentType("text/html;charset=utf-8");
		CommandContent c1 = new CommandContent();
		c1.setId(1);
		c1.setDescription("第一个");
		CommandContent c2 = new CommandContent();
		c2.setId(1);
		c2.setDescription("第二个");
		List<CommandContent> list = new ArrayList<>();
		list.add(c2);
		list.add(c1);
		JSONArray jsonArray = JSONArray.fromObject(list);
		resp.getWriter().print(jsonArray.toString());
	}