pentaho/pentaho-kettle · error · RuntimeException

Unable to clone import rule

Error message

Unable to clone import rule

What it means

BaseImportRule.clone() overrides Object.clone() to copy import rules; since CloneNotSupportedException is checked and the interface contract expects clonability, it rethrows it as a RuntimeException "Unable to clone import rule" with the cause attached. Reaching it means a rule subclass somehow inherited clone support incorrectly (effectively an internal invariant violation).

Solutions

  1. Ensure your rule class (and BaseImportRule hierarchy) implements java.lang.Cloneable.
  2. Inspect getCause() (CloneNotSupportedException) to identify which class in the hierarchy is not cloneable.
  3. In a custom rule, override clone() to use super.clone() and implement Cloneable rather than replacing the mechanism.
  4. As a workaround, perform a deep copy by re-creating the rule and copying its fields instead of relying on clone().

Example fix

// before
public class MyRule extends BaseImportRule { // no Cloneable handling
  public MyRule copy() { return (MyRule) clone(); }
}
// after
public class MyRule extends BaseImportRule implements Cloneable {
  public MyRule copy() { return (MyRule) super.clone(); }
}
Defensive patterns

Strategy: try-catch

Validate before calling

if (!(rule instanceof Cloneable)) {
  throw new IllegalStateException("Rule must implement Cloneable to be copied");
}

Try / catch

try {
  ImportRuleInterface copy = rule.clone();
} catch (RuntimeException e) {
  if (e.getMessage() != null && e.getMessage().contains("Unable to clone")) {
    log.error("Rule class does not support cloning: " + rule.getClass().getName(), e.getCause());
  } else {
    throw e;
  }
}

Prevention

When it happens

Trigger: Calling clone() (directly or via ImportRules copy/duplicate operations) on a rule whose class hierarchy does not properly support cloning — e.g. a subclass not implementing Clonenable transitively or super.clone() failing in a custom rule implementation.

Common situations: Custom import rule plugins that override clone or reshape the hierarchy without honoring the Cloneable contract; classloader/version mixing where the rule class was loaded in a way that broke the standard clone path.

Understand the failure class

Background: "This is a bug, please report it": internal invariant violations, unreachable panics, and SNH errors explained — this error's family across 47 libraries.

Related errors

AI-assisted analysis of pentaho/pentaho-kettle@f3058517a1 (2026-09-13). Data as JSON: /api/errors/03e3b8c746dffbfe. Report an issue: GitHub.

Appendix: source

Thrown at engine/src/main/java/org/pentaho/di/imp/rules/BaseImportRule.java:45

import org.w3c.dom.Node;

public abstract class BaseImportRule implements ImportRuleInterface {

  public static String XML_TAG = "rule";

  private String id;
  private boolean enabled;

  public BaseImportRule() {
    this.enabled = false;
  }

  @Override
  public ImportRuleInterface clone() {
    try {
      return (ImportRuleInterface) super.clone();
    } catch ( CloneNotSupportedException e ) {
      throw new RuntimeException( "Unable to clone import rule", e );
    }
  }

  @Override
  public boolean isUnique() {
    return true;
  }

  @Override
  public abstract List<ImportValidationFeedback> verifyRule( Object subject );

  @Override
  public String getXML() {
    StringBuilder xml = new StringBuilder();

    xml.append( XMLHandler.addTagValue( "id", id ) );
    xml.append( XMLHandler.addTagValue( "enabled", enabled ) );

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