pentaho/pentaho-kettle · error · RuntimeException

Unknown XML event:

Error message

Unknown XML event:

What it means

XMLFormatter.format() walks an XML stream (StaX) and throws this RuntimeException in its default case when it encounters an XML stream event type it does not explicitly handle (only start/end element, characters, etc. are supported).

Solutions

  1. Inspect the numeric event value in the message and map it to an XMLStreamConstants constant
  2. Add a case for the missing event type (e.g. XMLStreamConstants.COMMENT) in the switch to ignore or copy it
  3. Strip comments/processing instructions/doctype from the XML before formatting
  4. Set the input factory to coalesce/replacement-safe properties (e.g. P_LAZY? coalescing true, replacing entity references) so exotic events are not emitted
  5. Wrap format() in a try-catch if formatting is best-effort

Example fix

// before
default:
  throw new RuntimeException( "Unknown XML event: " + event );
// after
case XMLStreamConstants.PROCESSING_INSTRUCTION:
case XMLStreamConstants.COMMENT:
case XMLStreamConstants.DTD:
  break; // skip unhandled events
default:
  throw new RuntimeException( "Unknown XML event: " + event );
Defensive patterns

Strategy: try-catch

Validate before calling

// Detect constructs that map to unhandled events before formatting:
boolean risky = xml.contains( "<!DOCTYPE" ) || xml.contains( "<?" ) || xml.contains( "<!--" );

Try / catch

try {
  result = XMLFormatter.format( xml );
} catch ( RuntimeException e ) {
  if ( e.getMessage().startsWith( "Unknown XML event:" ) ) {
    // handle/strip the offending construct and retry, or skip formatting
  } else {
    throw e;
  }
}

Prevention

When it happens

Trigger: Formatting XML whose stream emits unhandled event types, e.g. PROCESSING_INSTRUCTION, DTD, ENTITY_REFERENCE, CDATA variants or COMMENT depending on handled cases.

Common situations: Formatting documents with DOCTYPE declarations, processing instructions (<?xml-stylesheet?>), comments or entity references; different StaX implementations surfacing more event types.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

AI-assisted analysis of pentaho/pentaho-kettle@f3058517a1 (2026-09-13). Data as JSON: /api/errors/8739ab080c330de4. Report an issue: GitHub.

Appendix: source

Thrown at core/src/main/java/org/pentaho/di/core/xml/XMLFormatter.java:143

            cdata.append( rd.getText() );
            wasSomething = true;
            break;
          case XMLStreamConstants.COMMENT:
            if ( !whitespacesOnly( str ) ) {
              wr.writeCharacters( str.toString() );
            } else if ( wasSomething ) {
              wr.writeCharacters( "\n" + prefix );
            }
            str.setLength( 0 );
            wr.writeComment( rd.getText() );
            wasSomething = true;
            break;
          case XMLStreamConstants.END_DOCUMENT:
            wr.writeCharacters( "\n" );
            wr.writeEndDocument();
            break;
          default:
            throw new RuntimeException( "Unknown XML event: " + event );
        }
      }

      wr.flush();

      return result.toString();
    } catch ( XMLStreamException ex ) {
      throw new RuntimeException( ex );
    } finally {
      try {
        if ( wr != null ) {
          wr.close();
        }
      } catch ( Exception ex ) {
      }
      try {
        if ( rd != null ) {
          rd.close();

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