ajax contentType:"application/json"

ajax发送请求后台要怎么接收 contentType:"application/json"
function add() {

$.ajax({
    type: "POST",
    dataType:"json",  
    contentType:"application/json; charset=UTF-8",
    url: "$appServer.get('sys_center/webservice/login/Login.htm')?random=$!{random}",
    data: JSON.stringify({"account":"admin","password":"c4ca4238a0b923820dcc509a6f75849b"}),
    success: function(result) {
        alert(result)
    }
}); 

}

@RequestMapping(value={"sys_center/webservice/login/Login"},headers = "Accept=application/json")
@ResponseBody
public void params(@RequestBody SysUser sysUser,HttpServletRequest request) {
System.out.println();
}
}
不知道怎么回事 接收不到诶 求解

System.out.printLn() 变量呢