Why Replacing MyBatis with MyBatis-Plus Can Break Your Java App—and How to Fix It

MyBatis Replaced by MyBatis-Plus

Background

An old project uses MySQL 5.7, MyBatis 3.5.0, and mysql-connector-java 5.1.26.

Why replace

A new developer found MyBatis cumbersome and decided to switch to MyBatis-Plus for simpler code.

Migration steps

Created table tbl_order with two rows, then switched the ORM to MyBatis-Plus 3.1.1 while keeping the same connector version.

Running com.qsl.OrderTest#orderListAllTest produced the exception “Conversion not supported for type java.time.LocalDateTime”.

Root cause analysis

The exception originates from MyBatis 3.5.1, which stopped handling LocalDateTime, LocalDate, and LocalTime conversions and delegated them to the JDBC driver. The driver version 5.1.26 does not support these types.

Upgrading mysql-connector-java to 5.1.37 adds support for the three Java time types, eliminating the error.

Further issues

After the upgrade, inserting a row with a NULL timestamp caused a NullPointerException. The stack trace showed that getTimestamp(columnIndex) returned NULL. Updating the driver to 5.1.42 resolved the problem.

Lesson

Component upgrades can introduce subtle incompatibilities. Always verify the compatibility of ORM libraries, JDBC drivers, and Java time types, and perform thorough testing after any version change.