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!

Anonymous said...

10 Years later...but thank you this was a huge help!