Ajax 返回值 中文乱码 解决

/** 
* 使用ajax检查用户是否存在 
*/ 
public void checkUser(){  
 
    try{  
        System.out.println("userName="+user.getUserName());  
        HttpServletResponse response=ServletActionContext.getResponse();  
        response.setContentType("text/xml;charset=utf-8");  
        response.setHeader("Cache-Control", "no-cache");  
       
        PrintWriter pw=response.getWriter(); //输出中文，这一句一定要放到response.setContentType("text/xml;charset=utf-8"),  response.setHeader("Cache-Control", "no-cache")后面，否则中文返回到页面是乱码  
        
        if(existUser.contains(user.getUserName()))  
        {  
            pw.print("存在");  
        }else{  
            pw.print("不存在");  
        }  
       
        pw.close();  
    }catch(IOException e){  
        e.printStackTrace();  
    }  
}

前台：
$.ajax({
type: "POST",
url : "${contextPath?if_exists}/resource/cascade.action",
data: {firstType:filrstTypevl},
contentType:"application/x-www-form-urlencoded;charset=utf-8",
dataType: "json", 
success: function(resp) {
$("#secondType option").remove();
$("#secondType").append("<option value=''>－－请选择二级分类－－</option>");
alert(resp);
$.each(resp,function(i){

$("#secondType").append("<option value="+resp[i].kdDetail+">"+resp[i].kdDesc+"</option>");
});
}
});