What causes "Unable to encode String in encoding [" + Const.XML_ENCODING + "]" in pentaho/pentaho-kettle?

Restore the JVM's charset configuration (remove unusual -Dfile.encoding or charset provider overrides) and restart the client.

pentaho/pentaho-kettle · error · RuntimeException

Unable to encode String in encoding [" + Const.XML_ENCODING…

Error message

Unable to encode String in encoding [" + Const.XML_ENCODING + "]

What it means

DragAndDropContainer.getXML serializes drag-and-drop payload bytes as Base64 using Const.XML_ENCODING; because that charset is a compile-time constant that Java must support, UnsupportedEncodingException is treated as an unrecoverable condition and rethrown as a RuntimeException. In practice this should never occur unless the JVM lacks the standard charset.

Solutions

Restore the JVM's charset configuration (remove unusual -Dfile.encoding or charset provider overrides) and restart the client.
Use a standard, unmodified JDK/JRE distribution for Spoon/PDI.
Verify Const.XML_ENCODING ('UTF-8') is supported: Charset.forName("UTF-8") in the same JVM.
Report as a bug if it occurs on a stock JVM — the code could safely use StandardCharsets.UTF_8.

Example fix

// before
new String(Base64.encodeBase64(data.getBytes(Const.XML_ENCODING)))
// after (no checked exception possible)
new String(Base64.encodeBase64(data.getBytes(StandardCharsets.UTF_8)))

Defensive patterns

Strategy: try-catch

Validate before calling

// confirm the JVM supports the XML encoding before operations
if (!Charset.isSupported(Const.XML_ENCODING)) {
  throw new IllegalStateException("JVM does not support " + Const.XML_ENCODING);
}

Try / catch

try { String xml = container.getXML(); }
catch (RuntimeException e) {
  if (e.getMessage() != null && e.getMessage().startsWith("Unable to encode String")) {
    log.error("Charset broken in JVM: reinstall/standard JDK");
  }
  throw e;
}

Prevention

Run Spoon/PDI on a stock JDK without charset provider overrides.
Avoid custom -Dfile.encoding experiments in production clients.
Add a startup charset sanity check (Charset.isSupported("UTF-8")).

When it happens

Trigger: getXML (public) is called to serialize the container for drag-and-drop transfer; data.getBytes(Const.XML_ENCODING) throws UnsupportedEncodingException — essentially only on a broken/limited JVM charset configuration (e.g. unusual charset provider setup).

Common situations: Custom JVM builds without standard encodings, exotic -Dfile.encoding/charset provider misconfiguration, instrumentation environments that intercept charset lookups.

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/4f2ff79ab496d110. Report an issue: GitHub.

Appendix: source

Thrown at ui/src/main/java/org/pentaho/di/core/dnd/DragAndDropContainer.java:148

  public String getXML() {
    try {
      StringBuilder xml = new StringBuilder( 100 );

      xml.append( XMLHandler.getXMLHeader() ); // UFT-8 XML header
      xml.append( XMLHandler.openTag( XML_TAG ) ).append( Const.CR );

      if ( id != null ) {
        xml.append( "  " ).append( XMLHandler.addTagValue( "ID", id ) );
      }
      xml.append( "  " ).append( XMLHandler.addTagValue( "DragType", getTypeCode() ) );
      xml.append( "  " ).append(
        XMLHandler
          .addTagValue( "Data", new String( Base64.encodeBase64( data.getBytes( Const.XML_ENCODING ) ) ) ) );
      xml.append( XMLHandler.closeTag( XML_TAG ) ).append( Const.CR );

      return xml.toString();
    } catch ( UnsupportedEncodingException e ) {
      throw new RuntimeException( "Unable to encode String in encoding [" + Const.XML_ENCODING + "]", e );
    }
  }

  /**
   * Construct a Drag and drop container from an XML String
   *
   * @param xml
   *          The XML string to convert from
   */
  public DragAndDropContainer( String xml ) throws KettleXMLException {
    try {
      Document doc = XMLHandler.loadXMLString( xml );
      Node dnd = XMLHandler.getSubNode( doc, XML_TAG );

      id = XMLHandler.getTagValue( dnd, "ID" );
      type = getType( XMLHandler.getTagValue( dnd, "DragType" ) );
      data =
        new String( Base64.decodeBase64( XMLHandler.getTagValue( dnd, "Data" ).getBytes() ), Const.XML_ENCODING );

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