How to bind table data with ArrayList from thymele

Question

I am trying to achieve below process in thymeleaf ( I am new to thymeleaf ) 1. Import csv file and display to user 2. After displaying data to user , User will have option to update those data in DB

Currently I am facing issue while passing table object to controller class

GET

@RequestMapping(value = "/samplepage", method = RequestMethod.GET)
public String bulkupload(Model model, HttpSession session) {

        AccountService wlaccservice = new AccountService();
        //ArrayList<AccountService> accountentry = new ArrayList<AccountService>();
        Accounts accountentry = new Accounts();

        model.addAttribute("accountentry", accountentry.getAccountentry());
        return "samplepage";

}

HTML (samplepage)

<tr class="table-row"  th:each="account : ${accountentry}">

                <td class="table-data" th:text="${account.accountnumber}"></td>
                <td class="table-data" th:text="${account.noofilc}"></td>

I have Form with button imporing CSV file and Update DB button

Setter and Getter class public AccountService {

private String accountnumber,noofilc;
    public String getAccountnumber() {
        return accountnumber;
    }
    public void setAccountnumber(String accountnumber) {
        this.accountnumber = accountnumber;
    }
    public String getNoofilc() {
        return noofilc;
    }

    .....
}

Array Class

public class Accounts {
    public ArrayList<AccountService> accountentry;

    public ArrayList<AccountService> getAccountentry() {
        return accountentry;
    }

    public void setAccountentry(ArrayList<AccountService> accountentry) {
        this.accountentry = accountentry;
    }

}

POST

@RequestMapping(value = "/samplepage", method = RequestMethod.POST)
public String bulkuploadPost(Model model,
        @ModelAttribute("samplepage") AccountService acctservice,
        @ModelAttribute  Accounts accountentry,
        HttpSession session, @RequestParam("file") MultipartFile file,HttpServletRequest request) {
    String action = request.getParameter("action");



        try {
            if (action.equalsIgnoreCase("Import CSV"))  // This part  to load data into html table accountentry which is work fine
            {
            byte[] bytes= file.getBytes();
            ByteArrayInputStream inputFilestream = new ByteArrayInputStream(bytes);
            BufferedReader br = new BufferedReader(new InputStreamReader(inputFilestream));
            String line = "";
            ArrayList<AccountService> arraylist = new ArrayList<AccountService>();
            while ((line = br.readLine()) != null) {
                TypeWhiteListAccountDetails accountDetails = new TypeWhiteListAccountDetails();
                accountDetails.Tablebulkupdate(line,arraylist); //getting array from here to load it in  accountentry variable 

            }
            br.close();
            accountentry.setAccountentry(arraylist);

        model.addAttribute("accountentry", accountentry.getAccountentry());


            }
            else if (action.equalsIgnoreCase("Start Update")) // after I am having data in accountentry start calling data from html to load in DB
            {

                model.addAttribute("accountentry", accountentry);
                System.out.println(accountentry.getAccountentry()); // always am getting as null for attribute accountentry
            }

        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return "samplepage";

}

I am always getting null value for the line which I mentioned above in comment,please help me on this part