filter.addField(new StringField("username", "base.user.table.username", ""));
ComboBoxField groupField = new ComboBoxField("userGroup", "base.user.label.usergroupkey", "");
groupField.addOption("", "*");
for (UserGroup userGroup : getUserGroups()) {
groupField.addOption(userGroup.getId(), userGroup.getGroupKey());
}
filter.addField(groupField);
ComboBoxField deletedField = new ComboBoxField("deleted", "base.user.label.deleted", "");