MyBatis Null Value Handling Guide

In MyBatis, the nullValue attribute can be used to set the method for handling empty values. This attribute can be used in the or tags in mapping files to specify a default value when the query result is null. For example:

<resultMap id="userResultMap" type="User">
    <result property="id" column="id" nullValue="0" />
    <result property="name" column="name" nullValue="Unknown" />
    <result property="age" column="age" nullValue="-1" />
</resultMap>

In the example above, if a field in the query result is null, MyBatis will set the value of that field to 0, Unknown, or -1 instead of keeping it as null.