Question

I defined the following drop down box in my page:
…

<td>
  <h:selectOneMenu id="bootenvironment1" value="#{detailModel.selectedBootenvironment1}"
                   disabled="#{detailModel.mode == detailModel.viewMode}">
    <f:selectItems value="#{detailModel.availableBootenvironments}"/>
  </h:selectOneMenu>
</td>

In my model I have:

...
  private Map<String, Bootenvironment> availableBootenvironments;

  public DefinitionDetailModel()
  {
    super();
  }

  public String getSelectedBootenvironment1()
  {
    if (((Definition) getAfterObject()).getBootenvironment1() != null)
    {
      return ((Definition) getAfterObject()).getBootenvironment1().getEnvironmentName();
    }

    return "--Please select one--";
  }

  public void setSelectedBootenvironment1( String selectedBootenvironment )
  {
    ((Definition) getAfterObject()).setBootenvironment1(availableBootenvironments.get(selectedBootenvironment));
  }
  ...

And in the controller I set the availableBootenvironments map:

private void fetchBootenvironments()
  {
    ...
    @SuppressWarnings( "unchecked" )
    List<Bootenvironment> bootenvironments = (List<Bootenvironment>) ...

    Map<String, Bootenvironment> availableBootenvironments = new HashMap<String, Bootenvironment>();

    availableBootenvironments.put("--Please select one--", null);

    for(Bootenvironment bootenvironment : bootenvironments)
    {
      availableBootenvironments.put(bootenvironment.getEnvironmentName(), bootenvironment);
    }

    ((DefinitionDetailModel) detailModel).setAvailableBootenvironments(availableBootenvironments);
  }

The problem is that when I click a button in the page (which is bound to an action), I get the error:

detailForm:bootenvironment1: Validation error: value is not valid.

I don’t understand where the error is; the value for selectItems is a map with the object’s name-field(so a string) as key and the object itself as value. Then the value for the default selected (value="#{detailModel.selectedBootenvironment1}") is a string too as you can see in the getter/setter method of the model.

Another problem (maybe related to the previous one) is that when the page first loads, the default selected value should be –Please select one— as the getBootenvironment1() returns null, but this does not happen: another one from the list is selected.

Can you please help me understanding what/where am I doing wrong?

EDIT

I implemented the Converter as you said:

@FacesConverter( forClass = Bootenvironment.class )
public class BootenvironmentConverter implements Converter
{

  @Override
  public String getAsString( FacesContext context, UIComponent component, Object modelValue ) throws ConverterException
  {
    return String.valueOf(((Bootenvironment) modelValue).getDbId());
  }

  @Override
  public Object getAsObject( FacesContext context, UIComponent component, String submittedValue ) throws ConverterException
  {
    List<Bootenvironment> bootenvironments = ... (get from DB where dbid=submittedValue)

    return bootenvironments.get(0);
  }

}

But now I have the following error:

java.lang.ClassCastException: java.lang.String cannot be cast to
ch.ethz.id.wai.bootrobot.bo.Bootenvironment

Answer 1

You will get this error when the selected item value doesn’t pass the equals() test on any of the available item values.

And indeed, you’ve there a list of Bootenvironment item values, but you’ve bound the property to a String which indicates that you’re relying on the Bootenvironment#toString() value being passed as submitted value and that you aren’t using a normal JSF Converter at all. A String can never return true on an equals() test with an Bootenvironment object.

You’d need to provide a Converter which converts between Bootenvironment and its unique String representation. Usually, the technical ID (such as the autogenerated PK from the database) is been used as the unique String representation.

@FacesConverter(forClass=Bootenvironment.class)
public class BootenvironmentConverter implements Converter {

    @Override
    public void getAsString(FacesContext context, UIComponent component, Object modelValue) throws ConverterException {
        // Write code to convert Bootenvironment to its unique String representation. E.g.
        return String.valueOf(((Bootenvironment) modelValue).getId());
    }

    @Override 
    public void getAsObject(FacesContext context, UIComponent component, Object submittedValue) throws ConverterException {
        // Write code to convert unique String representation of Bootenvironment to concrete Bootenvironment. E.g.
        return someBootenvironmentService.find(Long.valueOf(submittedValue));
    }

}

Finally, after implementing the converter accordingly, you should be able to fix the selectedBootenvironment1 property to be a normal property without any mess in getter/setter:

private Bootenvironment selectedBootenvironment1;

public Bootenvironment getSelectedBootenvironment1() {
    return selectedBootenvironment1;
}

public void setSelectedBootenvironment1(Bootenvironment selectedBootenvironment1) {
    this.selectedBootenvironment1 = selectedBootenvironment1;
}