springMVC：视图不会向控制器提交值

Question

I've got the following setup:

public class MyController extends BaseFormController {
  public MyController() {
    setCommandClass(MyObject.class);
    setCommandName("object");
    setSessionForm("true);
  }

  @Override
  protected ModelAndView onSubmit(HttpServletRequest request, HttpServletResponse response, Object command, BindException errors)
        throws Exception {
    MyObject o = (MyObject) command;
    ...
  }

MyObject has a member of type MyOtherObject which, in turn, has a member Set<String> foo :

public class MyObject {
  ...
  MyOtherObject otherObject;
  ...
}

public class MyOtherObject {
  ...
  Set<String> foo = new HashSet<String>();
  ...
}

and all corresponding setters and getters are implemented. Then I've got a view, written in jsp and:

<form:form method="POST" action="" commandName="object" ...
...
    <form:select path="otherObject.foo" multiple="multiple" size="4">
      <c:forEach var="entry" items="${listOfItems}">
        <option value="${entry.size}" <c:if test="${!entry.enabled}">disabled</c:if>>${entry.name}</option>
      </c:forEach>
    </form:select>
 ...
 </form:form>

My goal is to map the size s of some entries in the list to the set foo .

All other entries in the form are set to the values the user types in, so the overall syntax should be right. However when it comes to this multiple select form, which should be mapped to object.otherObject.foo, the controller acts as if no values whatsoever were ever provided in the view, ie even if I were to select multiple values from the box before hitting submit, the command object in the Controller still gets an empty otherObject.foo member.

Any ideas what may be causing this?

PS I also tried adding a Set<String> foo directly in MyObject and using it in the path="" of the view. It still didn't work out.

Answer 1

Did you override formBackingObject method? if yes, did you assign MyOtherObject to MyObject?

Answer 2

After a lot of poking around I found the solution - foo had to be declared as String[] foo and from there on spring took care of all the rest, just as expected. Beats me why spring would use "old-fashioned" arrays in this day and age but it apparently does.