pentaho/pentaho-kettle · error · KettleException

Can't encode object of class : className

Error message

Can't encode object of class : className

What it means

encodeAttributeValue only supports String, Double, Long/Integer, and Boolean objects; any other class (Date, BigDecimal, maps, POJOs) throws KettleException "Can't encode object of class ...". The metastore attribute store has a fixed value type set.

Solutions

1. Convert unsupported objects before storing: use toString()/ISO-8601 for Date, toPlainString() for BigDecimal
2. Encode as String and decode on read in your application code
3. Restrict element attributes to the supported types (String, Double, Long/Integer, Boolean)
4. Reject unsupported types at your API boundary with a clear validation error

Example fix

// before
attributes.put("created", new Date()); // throws
element.setProperty("created", attributes.get("created"));
// after
element.setProperty("created", new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'").format(new Date()));

boolean encodable(Object v) { return v == null || v instanceof String || v instanceof Double || v instanceof Long || v instanceof Integer || v instanceof Boolean; }

Object coerceEncodable(Object v) {
  if (v instanceof java.util.Date) return new java.text.SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'").format((java.util.Date) v);
  if (v instanceof java.math.BigDecimal) return ((java.math.BigDecimal) v).toPlainString();
  return v;
}

try { delegate.encodeAttributeValue(obj); } catch (KettleException e) { logError("Unsupported metastore attribute type: " + obj.getClass(), e); }

When it happens

Trigger: Calling encodeAttributeValue (via insertAttributes when saving a metastore element) with an attribute value that is not String, Double, Long, Integer, or Boolean.

Common situations: Putting Date or BigDecimal values into a metastore element; framework code storing arbitrary objects in element properties; API change returning a boxed type different from what was stored before.

Understand the failure class

Background: Type mismatch errors: IllegalArgumentException, TypeError and type guards across 150 open-source libraries — this error's family across 150 libraries.

Related errors

• Unable to parse attribute from attribute row: attributeRow
• Unknown data type : type
• AuthenticationManager.ConsumedTypeError
• AvroInput.Error.UnexpectedRecordFieldTypeAtNonExpansionPoint
• BaseStep.SafeMode.Exception.MixingTypes

AI-assisted analysis of pentaho/pentaho-kettle@f3058517a1 (2026-09-13). Data as JSON: /api/errors/995ae322e903ac2f. Report an issue: GitHub.

Appendix: source

Thrown at engine/src/main/java/org/pentaho/di/repository/kdr/delegates/KettleDatabaseRepositoryMetaStoreDelegate.java:421

    }
    if ( object instanceof Timestamp ) {
      return "T:" + new SimpleTimestampFormat(
        ValueMetaBase.DEFAULT_TIMESTAMP_FORMAT_MASK ).format( (Timestamp) object );
    }
    if ( object instanceof Date ) {
      return "D:" + new SimpleDateFormat( ValueMetaBase.DEFAULT_DATE_FORMAT_MASK ).format( (Date) object );
    }
    if ( object instanceof Double ) {
      return "N:" + Double.toString( (Double) object );
    }
    if ( object instanceof Long ) {
      return "I:" + Long.toString( (Long) object );
    }
    if ( object instanceof Boolean ) {
      return "B:" + ( ( (Boolean) object ) ? "true" : "false" );
    }

    throw new KettleException( "Can't encode object of class : " + object.getClass().getName() );
  }

  public ObjectId insertElement( IMetaStoreElementType elementType, IMetaStoreElement element ) throws MetaStoreException {
    try {

      LongObjectId elementId =
        repository.connectionDelegate.getNextID(
          quoteTable( KettleDatabaseRepository.TABLE_R_ELEMENT ),
          quote( KettleDatabaseRepository.FIELD_ELEMENT_ID_ELEMENT ) );
      RowMetaAndData table = new RowMetaAndData();

      table.addValue( new ValueMetaInteger(
        KettleDatabaseRepository.FIELD_ELEMENT_ID_ELEMENT ), elementId
        .longValue() );
      table.addValue( new ValueMetaInteger(
        KettleDatabaseRepository.FIELD_ELEMENT_ID_ELEMENT_TYPE ), Long
        .valueOf( elementType.getId() ) );
      table.addValue(

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