spring-mvc + jpa: data binding

Question

I have simple application which manages football teams and matches. I am using JPA, in the form editMatch.jsp i have property team_1, team_2 (instance of class Team) for choosing the team from the list. The problem is when editing match, the team_1 and team_2 dont select in the list, and after submitting the error message is: Property team_1 threw exception; nested exception is java.lang.NullPointerException. In the controller I am binding team_1, team_2 and I suppose that the error is somewhere between binding and initialization of the form.

editMatch.jsp

  <form:select path="team_1">
       <form:options items="${teamList}" itemLabel="name" itemValue="id"/>
  </form:select>

EditMatchController

public class EditMatchController extends SimpleFormController {
private MatchManager manager;
public EditMatchController() {}

@Override
protected void initBinder(HttpServletRequest request, ServletRequestDataBinder binder) throws Exception {


    Match match = (Match)binder.getTarget();
    SimpleDateFormat sdf = new SimpleDateFormat("dd-MM-yyyy");
    try{
        binder.registerCustomEditor(Date.class, "datum", new CustomDateEditor(sdf, false));
    } catch(Exception e){}

    binder.registerCustomEditor(Team.class,  new TeamPropertyEditor());
    binder.registerCustomEditor(Team.class,  new TeamPropertyEditor());

}

@Override
protected Map referenceData(HttpServletRequest request) throws Exception {
    Map<Object, Object> dataMap = new HashMap<Object, Object>();
    dataMap.put("teamList", manager.getTeams());
    return dataMap;
}

@Override
protected Object formBackingObject(HttpServletRequest request) throws Exception {
    int idMatch = Integer.parseInt(request.getParameter("id"));
    Match match_d = manager.getMatchById(idMatch);
    if (match_d == null) {
        throw new GenericException("Neplatný záznam.");
    }
    return match_d;
}


@Override
protected ModelAndView onSubmit(
        HttpServletRequest request,
        HttpServletResponse response,
        Object command,
        BindException errors) throws Exception {
    Match match = (Match)command;
    manager.updateMatch(match);
    RedirectView redirect = new RedirectView(getSuccessView());
    return new ModelAndView(redirect).addObject("message", match);
}

public void setManager(MatchManager manager) {
    this.manager = manager;
}

}

TeamPropertyEditor

public class TeamPropertyEditor extends PropertyEditorSupport {

private MatchManager manager;

public void setManager(MatchManager manager) {
    this.manager = manager;
}


@Override
public void setAsText(String text) throws IllegalArgumentException {
    if (text != null && text.length() > 0) {
            try {
                    Team team = this.manager.getTeamById(new Integer(text));
                    super.setValue(team);
            } catch (NumberFormatException ex) {
                    throw new IllegalArgumentException();
            }
    } else {
            super.setValue(null);
    }
}

@Override
public String getAsText() {
    Team team = (Team) super.getValue();
    return  (team != null ? (team.getId()+"").toString(): "");
}

}

edit:

errors.getFieldError("team_1"):

Field error in object 'match' on field 'team_1': rejected value [6]; codes [methodInvocation.match.team_1,methodInvocation.team_1,methodInvocation.model.Team,methodInvocation]; arguments [org.springframework.context.support.DefaultMessageSourceResolvable: codes [match.team_1,team_1]; arguments []; default message [team_1]]; default message [Property 'team_1' threw exception; nested exception is java.lang.NullPointerException]

Answer 1

You instantiate TeamPropertyEditor but don't call setManager() on it, so its manager field is null, therefore you get NPE when trying to call manager.getTeamById(...).