mybatis/mybatis-3 · error · ExecutorException

Could not process result for mapping: " + constructorMapping

Error message

Could not process result for mapping: " + constructorMapping

What it means

While building a constructor-arg value for constructor-based result mapping, either the nested-row load (getRowValue for a nested resultMap arg) or the TypeHandler read (typeHandler.getResult on the column) threw SQLException/ResultMapException. MyBatis wraps it with the offending constructorMapping printed, so you can see exactly which <arg> failed.

Source

Thrown at src/main/java/org/apache/ibatis/executor/resultset/DefaultResultSetHandler.java:831

            value = collection.getOriginalObject();
          } else {
            value = toSingleObj(result);
          }
        } else if (constructorMapping.getNestedResultMapId() != null) {
          final String constructorColumnPrefix = getColumnPrefix(columnPrefix, constructorMapping);
          final ResultMap resultMap = resolveDiscriminatedResultMap(rsw,
              configuration.getResultMap(constructorMapping.getNestedResultMapId()), constructorColumnPrefix);
          value = getRowValue(rsw, resultMap, constructorColumnPrefix,
              useCollectionConstructorInjection ? parentRowKey : null);
        } else {
          TypeHandler<?> typeHandler = constructorMapping.getTypeHandler();
          if (typeHandler == null) {
            typeHandler = typeHandlerRegistry.getTypeHandler(constructorMapping.getJavaType(), rsw.getJdbcType(column));
          }
          value = typeHandler.getResult(rsw.getResultSet(), prependPrefix(column, columnPrefix));
        }
      } catch (ResultMapException | SQLException e) {
        throw new ExecutorException("Could not process result for mapping: " + constructorMapping, e);
      }

      constructorArgTypes.add(parameterType);
      constructorArgs.add(value);

      foundValues = value != null || foundValues;
    }

    if (!foundValues) {
      return null;
    }

    if (useCollectionConstructorInjection) {
      // at least one of the nestedResultMaps contained a collection, we have to defer until later
      return new PendingConstructorCreation(resultType, constructorArgTypes, constructorArgs);
    }

    return objectFactory.create(resultType, constructorArgTypes, constructorArgs);

View on GitHub (pinned to 008069adb1)

Solutions

Inspect the printed constructorMapping and the cause exception: fix the named column (typo, missing alias, columnPrefix) or the javaType
Pin an explicit typeHandler on the <arg> if the default lookup picks the wrong one
Keep result column aliases in the SELECT in sync with the <arg column=...> names

Example fix

<!-- before -->
<constructor>
  <arg column="usr_name" javaType="string"/>  <!-- column is actually user_name -->
</constructor>
<!-- after -->
<constructor>
  <arg column="user_name" javaType="string"/>
</constructor>

Defensive patterns

Strategy: try-catch

Validate before calling

// Keep <arg column> names in sync with the SELECT aliases: assert at test time
try (SqlSession s = factory.openSession()) {
  s.selectList("sel.usersCtor"); // integration test exercising every constructor-mapped statement
}

Try / catch

catch (ExecutorException e) { if (e.getMessage() != null && e.getMessage().contains("Could not process result for mapping")) { log.error("Failing mapping: {}", e.getMessage(), e.getCause()); } throw e; }

Prevention

Column aliases in SQL must exactly match <arg column> values
Specify javaType and typeHandler explicitly on constructor args for non-obvious columns
Run a row-fetch smoke test per resultMap in CI

When it happens

Trigger: createParameterizedResultObject processes a <constructor><arg> whose column has no readable value, whose typeHandler is unresolved/mismatched, or whose nested resultMap fails — the catch on ResultMapException | SQLException converts it to this ExecutorException with the mapping as context.

Common situations: Constructor arg column name typo so rs.getXxx fails; jdbcType/javaType mismatch in the constructor arg (e.g. mapping a VARCHAR to int); nested collection constructor args hitting their own mapping errors; stored procs returning fewer columns than mapped after schema change.

Related errors

AI-assisted analysis of mybatis/mybatis-3@008069adb1 (2026-08-14). Data as JSON: /api/errors/8004b28d336e3007. Report an issue: GitHub.