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Type Handlers

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A Type Handler converts between Java types and database column types for reading and writing. For example, using String to read and write a VARCHAR column.

Type Handlers can effectively handle special database types such as geospatial types, currency types, timezone-aware times, enums, and serialization.

Type Handler Selection Priority​

When no Type Handler is explicitly specified, dbVisitor automatically selects one in the following priority order:

  1. Java type + JDBC type (combo type table)
  2. Java type (single type table), most common
  3. JDBC type
  4. Use UnknownTypeHandler (fallback)
Example: specify via javaType
select * from users where name = #{name, javaType=java.lang.String}
Example: specify via javaType + jdbcType
select * from users where name = #{name, jdbcType=varchar, javaType=java.lang.String}
  • JDBC type VARCHAR + Java type java.lang.String maps to StringTypeHandler (see the combo type table).
info
  • Most Type Handlers do not require a JDBC type when reading or writing data.
  • Usually you only need to specify the Java type for parameter setting and result set reading (stored procedure OUT parameters are the main exception).

If the built-in Type Handlers do not meet your needs, you can create a custom Type Handler to handle special cases.

Usage Guide​