1. mybatis where条件 is null
xml
<if test="strA != null and strA != '' and strA != 'ISNULL'"> and te.str_a = #{strA}</if>
<if test="strA != null and strA == 'ISNULL'"> and te.str_a is null</if>
2.if判断变量名
xml
<if test="aaaBbb == @com.xx.aa.constant.XXXConstant@CC_DD_EE "></if>
3. 更新变量赋值
sql
update T_XXX set AA_BB = '${@com.xx.aa.constant.XXXConstant@CC_DD_EE}'