mybatis/mybatis-3 · error · ExecutorException

Error cloning cache key. Cause: {}

Error message

Error cloning cache key.  Cause: {}

What it means

While combining the row cache key of a nested result with its parent row key (used to deduplicate nested rows for collections/associations), cloning the CacheKey threw CloneNotSupportedException. CacheKey implements clone() and this is a defensive wrap that in practice should never fire; if it does, it indicates a corrupted/patched mybatis build or an unexpected runtime environment rather than a user mapping error.

Source

Thrown at src/main/java/org/apache/ibatis/executor/resultset/DefaultResultSetHandler.java:1519

      } else {
        createRowKeyForUnmappedProperties(resultMap, rsw, cacheKey, columnPrefix);
      }
    } else {
      createRowKeyForMappedProperties(resultMap, rsw, cacheKey, resultMappings, columnPrefix);
    }
    if (cacheKey.getUpdateCount() < 2) {
      return CacheKey.NULL_CACHE_KEY;
    }
    return cacheKey;
  }

  private CacheKey combineKeys(CacheKey rowKey, CacheKey parentRowKey) {
    if (rowKey.getUpdateCount() > 1 && parentRowKey.getUpdateCount() > 1) {
      CacheKey combinedKey;
      try {
        combinedKey = rowKey.clone();
      } catch (CloneNotSupportedException e) {
        throw new ExecutorException("Error cloning cache key.  Cause: " + e, e);
      }
      combinedKey.update(parentRowKey);
      return combinedKey;
    }
    return CacheKey.NULL_CACHE_KEY;
  }

  private List<ResultMapping> getResultMappingsForRowKey(ResultMap resultMap) {
    List<ResultMapping> resultMappings = resultMap.getIdResultMappings();
    if (resultMappings.isEmpty()) {
      resultMappings = resultMap.getPropertyResultMappings();
    }
    return resultMappings;
  }

  private void createRowKeyForMappedProperties(ResultMap resultMap, ResultSetWrapper rsw, CacheKey cacheKey,
      List<ResultMapping> resultMappings, String columnPrefix) throws SQLException {
    for (ResultMapping resultMapping : resultMappings) {

View on GitHub (pinned to 008069adb1)

Solutions

1. Verify only one MyBatis jar is on the classpath and it is the official unmodified artifact (mvn dependency:tree | grep mybatis).
2. Clean and rebuild to eliminate stale instrumented classes.
3. If the exception occurs, report a bug to the MyBatis project with the full stack trace — stock CacheKey cannot throw this.

// verify a clean classpath at startup
new org.apache.ibatis.cache.CacheKey().clone(); // must never throw; smoke-test the mybatis jar

catch (ExecutorException e) when e.getMessage().contains("Error cloning cache key") -> treat as environment/classpath defect: fail startup and require dependency audit rather than continuing with possibly-corrupted mapping state.

When it happens

Trigger: Nested result mapping with multiple id/contributing columns on both parent and nested rows (both rowKey and parentRowKey update counts > 1) so combineKeys performs rowKey.clone(); clone() throws CloneNotSupportedException.

Common situations: Essentially untriggerable with stock MyBatis (CacheKey.clone() never throws); appears only with modified classpath versions, old forked copies of mybatis on the classpath shadowing the real one, or exotic bytecode transformations.

Related errors

• Unknown statement type: {}
• Unknown execution method for: {name}
• Mapper method '{name}' attempted to return null from a metho
• Mapper method '{name}' has an unsupported return type: {retu
• method {name} needs either a @ResultMap annotation, a @Resul

AI-assisted analysis of mybatis/mybatis-3@008069adb1 (2026-08-14). Data as JSON: /api/errors/4348c2a6f8978ddf. Report an issue: GitHub.