ibatis自动生成char(32)的key

<insert id="InsertCat" parameterClass="Cat" >
    <selectKey resultClass="string" type="pre" property="Id" >
        select replace(CONVERT(nvarchar(36), newid()), '-','') as value
    </selectKey>
    insert into Cat ( name, sex, weight, catid )
    values
    (#Name#, #Sex#, #Weight#, #Id#)
</insert>