Unsigned Fields

MySql supports both signed, and unsigned, numeric fields. These are not JDBC types, so MyBatis generator cannot automatically account for these types of fields. The Java data types are always signed. This can lead to a loss of precision when using unsigned fields. The solution is to provide a <columnOverride> for any unsigned numeric field in MySql. Here is an example of how to deal with an unsigned bigint field in MySql:

  <table tableName="ALLTYPES" >
    <columnOverride column="UNSIGNED_BIGINT_FIELD" javaType="java.lang.Object" jdbcType="LONG" />
  </table>

You will have to cast the returned value to the appropriate type yourself (in this case, java.math.BigInteger).

Catalogs and Schema

MySql does not properly support SQL catalogs and schema. If you run the create schema command in MySql, it actually creates a database - and the JDBC driver reports it back as a catalog. But MySql syntax does not support the standard catalog..table SQL syntax.

For this reason, it is best to not specify either catalog or schema in generator configurations. Just specify table names and specify the database in the JDBC URL.

If you are using version 8.x of Connector/J you may notice that the generator attempts to generate code for tables in the MySql information schemas (sys, information_schema, performance_schema, etc.) This is probably not what you want! To disable this behavior, add the property "nullCatalogMeansCurrent=true" to your JDBC URL.

For example:

    <jdbcConnection driverClass="com.mysql.jdbc.Driver" connectionURL="jdbc:mysql://localhost/my_schema"
            userId="my_user" password="my_password">
        <property name="nullCatalogMeansCurrent" value="true" />
    </jdbcConnection>