How to edit an array in Form from JSTL

I have to do something and I don't know how, could you help me, please?

I have a form where there is an array of positions. Here is the code:

public class DataFieldForm  implements Serializable {   

private int id;

private List<Position> positions = new ArrayList<Position>();

public List<Position> getPositions() {
        return positions;
    }

public void setPositions(List<Position> positions) {
    this.positions = positions;
}
}

... (There are more getters and setter for id I have hidden)

And now in my JSP I want to show the data contained in the array but linked to the Form so any change made bu the user would be reflected in the form, so I tried with the following:

<form:form action="${actionManageRegisteresDataFieldURL}" commandName="registeredDataForm"  method="POST">

<c:forEach items="${positions}" var="position">
                    <div class="datosregistradoscampo-items">

                        <div class="datosregistradoscampo-item">

                            <form:input class="nuevocampoformulario-input" name="position.id" type="text" autocomplete="off" path="position.id" id="position.id" size="20" />                           
                        </div>

                    </div>  
                    </c:forEach>

But it doesnt work... so I'm getting something completely wrong...

Thanks in advance.