ModelAttribute not working with lists in spring - spring

Question

I want to bind a List using ModelAttribute. The list contains objects of type Transaction each of which contains transactionid (type int). This is my controller code:
#RequestMapping(value = "/approvecreditdebit.do", method = RequestMethod.POST)
public ModelAndView doActions(HttpServletRequest request,
#ModelAttribute("clc") Clc transactionList, BindingResult result,
ModelMap model) {
/*
* switch (action) { case "approve":
*/
System.out.println("Obj = " + transactionList.getClass());
System.out.println("Val = " + transactionList.getTransactionList());
Users users = new Users();
return new ModelAndView("internal","internal",users);
}
This is my jsp code:
<form:form action="approvecreditdebit.do" method="POST"
modelAttribute="clc">
<table border="1">
<tr>
<th>no</th>
<th>ID</th>
</tr>
<c:forEach items="${clc.transactionList}"
var="transaction" varStatus="status">
<tr>
<td>${status.index}</td>
<td><input name = "transaction[${status.index}].transactionId"
value="${transaction.transactionId}" /></td>
</tr>
</c:forEach>
</table>
<br>
<br>
<center>
<input type="submit" value="approve" />
</center>
</form:form>
This is the Clc class:
public class Clc{
private List<Transaction> transactionList;
public List<Transaction> getTransactionList() {
return transactionList;
}
public void setTransactionList(List<Transaction> transactionList) {
this.transactionList = transactionList;
}
}
The value of transactionList is not being set to the values received from the form. I receive the following error:
Request processing failed; nested exception is java.lang.NullPointerException
I tried searching for the solution on google and got a lot of solutions from stackoverflow but none of them seem to work.

Answer 1

Try something like this (notice the use of <form:input>). I just tried it on a simple Spring MVC app and it works (list is not null and has the values from the form when I try to access it in my POST method).
<c:forEach var="transaction" varStatus="status" items="${clc.transactionList}">
<tr>
<td>${status.index}</td>
<td><form:input path="transactionList[${status.index}].id" /></td>
</tr>
</c:forEach>