Replacing MyBatis with MyBatis-Plus: Troubleshooting LocalDateTime Conversion Issues and Version Compatibility

Background

An existing project uses MySQL 5.7.36, MyBatis 3.5.0, and mysql‑connector‑java 5.1.26. A new developer finds MyBatis cumbersome and decides to replace it with MyBatis‑Plus 3.1.1 while keeping other component versions unchanged.

Migration Steps and Initial Failure

A demo table tbl_order is created and populated with two rows. When running com.qsl.OrderTest#orderListAllTest , a TransientDataAccessResourceException occurs, indicating "Conversion not supported for type java.time.LocalDateTime".

org.springframework.dao.TransientDataAccessResourceException: Error attempting to get column 'pay_time' from result set. Cause: java.sql.SQLException: Conversion not supported for type java.time.LocalDateTime ...

The stack trace shows the failure originates from the JDBC driver, not MyBatis‑Plus itself.

Root Cause Analysis

MyBatis 3.5.1 stopped handling LocalDateTime , LocalDate , and LocalTime conversions, delegating them to the JDBC driver. The used driver version (5.1.26) does not support these Java 8 time types, leading to the exception.

Upgrading mysql‑connector‑java to 5.1.37 adds support for the missing types, and the test runs successfully.

Further Issues and Fixes

After a version upgrade, inserting a record with a NULL pay_time triggers another exception. Investigating the driver source confirms that getObject throws a conversion error when the type is unsupported.

Upgrading the driver further to 5.1.42 resolves the null‑handling problem.

Additional Case: File‑Generation Validation Bug

The author shares a separate incident where a validation bug in a file‑generation service was “fixed” but later caused production failures due to hidden dirty data. The story highlights the risk of changing code without comprehensive testing.

Conclusion

Component upgrades can have far‑reaching effects; careful version compatibility checks and thorough testing are essential. When migrating MyBatis to MyBatis‑Plus, ensure the JDBC driver supports Java 8 time types, and avoid unnecessary changes unless fully validated.