ajax不执行success回调只执行error; 但每次点击数据库中都能查询到值

代码如下: 

$.ajax({
type:"POST",
url:"ActileTypeInsertAction.action",
dataType:"JSON",
async:false,
timeout:2000,
data:{ActileTypeName:$("input[name='ActileTypeName']").val()},
success:function(data,textStatus){
alert(myData);
if(data.returnstr=="1")
{
alert("XXXX");}
else{
$("span[name='mgs']").html("XXXXX");
alert(data.returnstr);
}
},
error:function(XMLHttpRequest,textStatus,errorThrown){
alert("请求对象XMLHttpRequest: "+XMLHttpRequest);
alert("error:"+textStatus);
alert("异常对象errorThrown:"+errorThrown);
}
});

action:

HttpServletRequest request=ServletActionContext.getRequest();
HttpServletResponse response=ServletActionContext.getResponse();
PrintWriter out=null;
response.setContentType("text/html;charset=UTF-8");
response.setHeader("Cache-Control", "no-Cache");
out=response.getWriter();
String returnstr="系统错误";
String ActileTypeName=request.getParameter("ActileTypeName");
if(("".equals(ActileTypeName))||(ActileTypeName==null))
{
returnstr="非法进入";
}
else
{
ActileTypeDao atd=new ActileTypeDao();
ArticleTypeBean atb=new ArticleTypeBean();
atb.setTypeName(java.net.URLDecoder.decode(request.getParameter("ActileTypeName"),"UTF-8"));
boolean flag=atd.InsertActileType(ActileTypeName);
if(flag)
{
returnstr="0";
}
else
{
returnstr="1";
}
}
out.println("{returnstr:'" + returnstr + "'}");
out.close();
return null;

求各位大侠指点