mybatis中判断字符串

mapper.xml中判断字符串

<if test="flag == 'N'">

AND cust.certificate_no NOT IN (#{idCards})

</if>

这种写法会报：org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.exceptions.PersistenceException: 
### Error querying database.  Cause: java.lang.NumberFormatException: For input string: "N"
### Cause: java.lang.NumberFormatException: For input string: "N"

因为mybatis映射文件，是使用的ognl表达式，所以会把‘Y'解析为char，java是强类型的语言，不能这样写，正确写法：

<if test="flag == 'N'.toString()">

AND cust.certificate_no NOT IN (#{idCards})

</if>

或者

<if test='flag == "N"'>

AND cust.certificate_no NOT IN (#{idCards})

</if>