Spring 3: Select value to enum value mapping - spring

Question

I have a very simple scenario to handle. An enum is created to represent a set of options for select control. The select control needs to have a prompt mapped to '-' as the prompt value. The corresponding enum does not have this dash. When page is submitted with select control still sitting at the prompt, exception is thrown. How do you handle such cases?
Page:
<select id="filterUserAccessLevel" name="filterUserAccessLevel">
<option value="-">Select Value</option>
<option value="DEPOSITOR">Depositor</option>
<option value="READER">Reader</option>
<option value="AUTHOR">Author</option>
<option value="EDITOR">Editor</option>
<option value="ADMINISTRATOR">Administrator</option>
</select>
<input type="submit" name="resetFilter" value="<spring:message code="common.filterResetButtonLabel" />" />
UserAccessLevel enum:
public enum UserAccessLevel {
DEPOSITOR("DEPOSITOR"),
READER("READER"),
AUTHOR("AUTHOR"),
EDITOR("EDITOR"),
ADMINISTRATOR("ADMINISTRATOR");
private String code;
private UserAccessLevel(String code) {
this.code=code;
}
public String getCode() {
return this.code;
}
}
Controller:
#RequestMapping(value="/userIndex/", method=RequestMethod.POST, params="resetFilter")
public void resetFilter(#ModelAttribute("userIndexBean") UserIndexBean bean, Model model) {
System.out.println("resetFilter()");
bean.resetFilterSection();
loadBean(1, bean, model);
}
Exception:
Field error in object 'userIndexBean' on field 'filterUserAccessLevel': rejected value [-];

Answer 1

Why is necessary an option mapped to "-"? Can't it be just an empty String?
In this case, I think that the simplest solution is:
<option value="">Select Value</option>
.
#RequestMapping("userIndex")
public void resetFilter(#RequestParam(required = false) UserAccessLevel filterUserAccessLevel) {
...
}