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Forum: Seam Users Forum ListTopic List
29. Jul 2008, 04:19 CET | Link

Well, this is not strictly related to Seam I think but more related to JSF. In particular, in a Seam JSF-based application I am building, I found that converter seems not being called at all if the value expression returns null.

The details: I have an @entity with a property whose type is a java.util.Date. However, this property can be null in the database, but on rendering I would like it to be displayed - Nil - rather than null or empty string. So I made a custom Converter that extends DateTimeConverter that returns that string when the value is null, like so: 


@Converter(id="lastLogin")
public class LastLoginDateConverter extends DateTimeConverter {

	/* (non-Javadoc)
	 * @see javax.faces.convert.Converter#getAsString(javax.faces.context.FacesContext, javax.faces.component.UIComponent, java.lang.Object)
	 */
	@Override
	public String getAsString(FacesContext arg0, UIComponent arg1, Object arg2) {
		// TODO Auto-generated method stub
		if (arg2 != null && !(arg2 instanceof java.util.Date)) {
			throw new ConverterException("Not valid date");
		}
		String s = super.getAsString(arg0, arg1, arg2);
		return (s.isEmpty() ? "- Nil -" : s);
	}

}

and install it on the h:outputText on the JSP page where I would like it to be with a converter attribute. However, it seems like the null/empty part never get called. In fact, I tried comment-out everything in the converter and simply return 'xxxxx' and only the non-null values are affected.

I searched the Web and someone suggested the specification for JSF 1.1 seems to require implementations to bypass converter when the value is null, but I suppose Seam 2.0.x ships JSF 1.2? I checked JSF 1.2 specification and I could not find the same requirements, but still that would not explain why converter is bypassed with null values.

So, being new with JSF/Seam-based development, is making a JSF converter for presentation appropriate for this situation, or is there a better way?

3 Replies:
29. Jul 2008, 13:10 CET | Link

Yup, converters aren't run in this case.

I'll bring it up as an improvement to make to JSF 2.

 

Read about how to report a bug.
02. Oct 2008, 13:45 CET | Link

Hi Pete,

I can't believe that is not possible yet. It's such a shortcoming. Actually converters where called until you switched the jsf libraries in seam.

I used a converter like this to be able to type in NULL into a textfield to actually set the value to null. If I typed in an empty string, then this would be treated as such.

I noticed that in the new sun jsf libraries a converter is never run if the value of the field is null. I think that is really bad.

This converter used to work for NULLvalues with apache myfaces: 


public class NullTextFieldConverter implements Converter
{
  
  public Object getAsObject(FacesContext facesContext, UIComponent uiComponent, String value)
  {

    if (facesContext == null)
    {
      throw new NullPointerException("facesContext");
    }
    if (uiComponent == null)
    {
      throw new NullPointerException("uiComponent");
    }

    return stringToValue(value);
  }

  protected Object stringToValue(String value)
  {
    if (value != null && value.equals("NULL"))
      return null;

    return value;
  }

  public String getAsString(FacesContext facesContext, UIComponent uiComponent, Object value)
  {
   // Note, this function is never called for null values! This used to work with myfaces but not with the sun libs
    
    System.out.println("getAsString " + value);
   

    if (facesContext == null)
    {
      throw new NullPointerException("facesContext");
    }
    if (uiComponent == null)
    {
      throw new NullPointerException("uiComponent");
    }
    return valueToString(value);
  }

  
  protected String valueToString(Object value)
  {
    
    if (value == null)
    {
      return "NULL";
    }
    if (value instanceof String)
    {
      return (String) value;
    }
    
    return value.toString();
  }
}