HI,

I believe i have come across a defect in the OIDCAttributeMapperHelper class.  The issue occurs when you have a String Attribute which is set with no value using a custom federation provider.  The code blows up on the line:
return attributeValue.toString(); (Line 64)

in the section of code:
String type = mappingModel.getConfig().get(JSON_TYPE);
if (type == null) return attributeValue;
if (type.equals("boolean")) {
     if (attributeValue instanceof Boolean) return attributeValue;
     if (attributeValue instanceof String) return Boolean.valueOf((String)attributeValue);
     throw new RuntimeException("cannot map type for token claim");
} else if (type.equals("String")) {
     if (attributeValue instanceof String) return attributeValue;
     return attributeValue.toString();
} else if (type.equals("long")) {
     if (attributeValue instanceof Long) return attributeValue;
     if (attributeValue instanceof String) return Long.valueOf((String)attributeValue);
     throw new RuntimeException("cannot map type for token claim");
} else if (type.equals("int")) {
     if (attributeValue instanceof Integer) return attributeValue;
     if (attributeValue instanceof String) return Integer.valueOf((String)attributeValue);
     throw new RuntimeException("cannot map type for token claim");
}
return attributeValue;

The attribute exists with no value which causes the attrbuteValue to be null and there is no check for null at that point.  I would expect it would return empty string if the type is string and the value is null.

Thanks,
jeff