What is the function of the MyBatis type handler?

The role of MyBatis type handlers is to convert Java types to database types and vice versa. In MyBatis, there are differences between Java types and database types, such as the mapping relationship between the Date type in Java and the TIMESTAMP type in the database. Type handlers can address these differences by converting Java objects to types recognizable by the database, and converting query results from database types to Java objects.

The main purpose of a type handler is:

1. Convert Java objects to database types: When performing insertion or update operations through MyBatis, type handlers can convert Java objects to the corresponding database types, allowing them to be stored in the database.
2. Convert database types to Java objects: When retrieving data from a database, type handlers can convert the database types into corresponding Java objects, allowing them to be used in a Java program.
3. Handling null values: The type handler is able to handle null values by converting them into values that the database can accept, or by converting null values from the database into null in Java.
4. Enum type handling: Type handlers can convert Java enum types to strings or integers in the database, allowing them to be properly stored and retrieved.

By customizing type handlers, MyBatis’ ability to convert types can be expanded to support a wider range of mappings between Java types and database types.