Monday, June 25, 2012

Multi value fields and Beans in XPages

I had an issue with multi value fields bound to bean fields in an XPages I worked on.

I got this error message on refresh:
java.lang.IllegalArgumentException: argument type mismatch

The issue turned out to be a somewhat inconsistent underlying API. When the field is empty, or has single value, it tries to set a string. When there are multiple values, it tries to set a list.

To work around the issue, have the getter return an Object, and the setter accept an object.

public Object getInputMulti() {
 return this.inputMulti;
@SuppressWarnings( "unchecked" )
public void setInputMulti( Object inputMulti ) {
 if( inputMulti == null ){
  this.inputMulti = null;
 if( inputMulti instanceof String ) {
  Vector inputNameList = new Vector();
  inputNameList.add( (String) inputMulti );
  this.inputMulti = inputNameList;  
 if( inputMulti instanceof List ) {
  this.inputMulti = (Vector) inputMulti;

You can have the translation for the setter be done in a utility method. E.g.
public static Vector translateToVector( Object object ){
 if( object instanceof String ){
  Vector list = new Vector();
  list.add( object );
  return list;
 if( object instanceof List ){
  return (Vector)object;
 return null;

Then, for the setter:

@SuppressWarnings( "unchecked" )
public void setInputMulti( Object inputMulti ) {
  this.inputMulti = UtilityClass.translateToVector( inputMulti );

Example of multi value fields: Checkbox group, multi value fields (fields with multipleSeparator), list boxes.


Jeff Byrd said...

Thanks for this post Tommy. It saved me a lot of time this morning!

-- Jeff

Cameron Gregor said...

Thanks for this, exactly what I was looking for! I also saw it through the defect list on openntf

Anonymous said...

And where to enter this code?

Unknown said...

Thank you so much... You save my day!