mybatis异常: invalid comparison: java.util.ArrayList and java.lang.String] with root cause

mybatis中使用动态sql，报错： invalid comparison: java.util.ArrayList and java.lang.String] with root cause

是由于  list != ' ' 导致的,引起了集合与string类型的比较

<if test="lsit != null and list != ''">

     B.COMMID IN (

     <foreach collection="list" item="commId" index="index" separator=",">

        #{commId,jdbcType=VARCHAR}

     </foreach>

     )

</if>

修改为

<if test="lsit != null and list.size > 0">

     B.COMMID IN (

     <foreach collection="list" item="commId" index="index" separator=",">

        #{commId,jdbcType=VARCHAR}

     </foreach>

     )

</if>